xref: /btstack/src/classic/avrcp.c (revision 227d16a53b98d7af4a4ae1aaa120a80c32074b9e)
1 /*
2  * Copyright (C) 2016 BlueKitchen GmbH
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  *
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. Neither the name of the copyright holders nor the names of
14  *    contributors may be used to endorse or promote products derived
15  *    from this software without specific prior written permission.
16  * 4. Any redistribution, use, or modification is done solely for
17  *    personal benefit and not for any commercial purpose or for
18  *    monetary gain.
19  *
20  * THIS SOFTWARE IS PROVIDED BY BLUEKITCHEN GMBH AND CONTRIBUTORS
21  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MATTHIAS
24  * RINGWALD OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
26  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
27  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
30  * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  *
33  * Please inquire about commercial licensing options at
34  * [email protected]
35  *
36  */
37 
38 #define __BTSTACK_FILE__ "avrcp.c"
39 
40 #include <stdint.h>
41 #include <stdio.h>
42 #include <stdlib.h>
43 #include <string.h>
44 
45 #include "btstack.h"
46 #include "classic/avrcp.h"
47 
48 #define PSM_AVCTP                       BLUETOOTH_PROTOCOL_AVCTP
49 #define PSM_AVCTP_BROWSING              0x001b
50 
51 /*
52 Category 1: Player/Recorder
53 Category 2: Monitor/Amplifier
54 Category 3: Tuner
55 Category 4: Menu
56 */
57 
58 /* controller supported features
59 Bit 0 = Category 1
60 Bit 1 = Category 2
61 Bit 2 = Category 3
62 Bit 3 = Category 4
63 Bit 4-5 = RFA
64 Bit 6 = Supports browsing
65 Bit 7-15 = RFA
66 The bits for supported categories are set to 1. Others are set to 0.
67 */
68 
69 /* target supported features
70 Bit 0 = Category 1
71 Bit 1 = Category 2
72 Bit 2 = Category 3
73 Bit 3 = Category 4
74 Bit 4 = Player Application Settings. Bit 0 should be set for this bit to be set.
75 Bit 5 = Group Navigation. Bit 0 should be set for this bit to be set.
76 Bit 6 = Supports browsing*4
77 Bit 7 = Supports multiple media player applications
78 Bit 8-15 = RFA
79 The bits for supported categories are set to 1. Others are set to 0.
80 */
81 
82 static uint16_t avrcp_cid_counter = 1;
83 
84 // TODO: merge with avdtp_packet_type_t
85 typedef enum {
86     AVRCP_SINGLE_PACKET= 0,
87     AVRCP_START_PACKET    ,
88     AVRCP_CONTINUE_PACKET ,
89     AVRCP_END_PACKET
90 } avrcp_packet_type_t;
91 
92 typedef enum {
93     AVRCP_COMMAND_FRAME = 0,
94     AVRCP_RESPONSE_FRAME
95 } avrcp_frame_type_t;
96 
97 static int record_id = -1;
98 static uint8_t   attribute_value[1000];
99 static const unsigned int attribute_value_buffer_size = sizeof(attribute_value);
100 
101 static const char * default_avrcp_controller_service_name = "BTstack AVRCP Controller Service";
102 static const char * default_avrcp_controller_service_provider_name = "BTstack AVRCP Controller Service Provider";
103 static const char * default_avrcp_target_service_name = "BTstack AVRCP Target Service";
104 static const char * default_avrcp_target_service_provider_name = "BTstack AVRCP Target Service Provider";
105 
106 static btstack_packet_handler_t avrcp_callback;
107 
108 static avrcp_context_t avrcp_controller_context;
109 
110 static const char * avrcp_subunit_type_name[] = {
111     "MONITOR", "AUDIO", "PRINTER", "DISC", "TAPE_RECORDER_PLAYER", "TUNER",
112     "CA", "CAMERA", "RESERVED", "PANEL", "BULLETIN_BOARD", "CAMERA_STORAGE",
113     "VENDOR_UNIQUE", "RESERVED_FOR_ALL_SUBUNIT_TYPES",
114     "EXTENDED_TO_NEXT_BYTE", "UNIT", "ERROR"
115 };
116 const char * avrcp_subunit2str(uint16_t index){
117     if (index <= 11) return avrcp_subunit_type_name[index];
118     if (index >= 0x1C && index <= 0x1F) return avrcp_subunit_type_name[index - 0x10];
119     return avrcp_subunit_type_name[16];
120 }
121 
122 static const char * avrcp_event_name[] = {
123     "ERROR", "PLAYBACK_STATUS_CHANGED",
124     "TRACK_CHANGED", "TRACK_REACHED_END", "TRACK_REACHED_START",
125     "PLAYBACK_POS_CHANGED", "BATT_STATUS_CHANGED", "SYSTEM_STATUS_CHANGED",
126     "PLAYER_APPLICATION_SETTING_CHANGED", "NOW_PLAYING_CONTENT_CHANGED",
127     "AVAILABLE_PLAYERS_CHANGED", "ADDRESSED_PLAYER_CHANGED", "UIDS_CHANGED", "VOLUME_CHANGED"
128 };
129 const char * avrcp_event2str(uint16_t index){
130     if (index <= 0x0d) return avrcp_event_name[index];
131     return avrcp_event_name[0];
132 }
133 
134 static const char * avrcp_operation_name[] = {
135     "NOT SUPPORTED", // 0x3B
136     "SKIP", "NOT SUPPORTED", "NOT SUPPORTED", "NOT SUPPORTED", "NOT SUPPORTED",
137     "VOLUME_UP", "VOLUME_DOWN", "MUTE", "PLAY", "STOP", "PAUSE", "NOT SUPPORTED",
138     "REWIND", "FAST_FORWARD", "NOT SUPPORTED", "FORWARD", "BACKWARD" // 0x4C
139 };
140 const char * avrcp_operation2str(uint8_t index){
141     if (index >= 0x3B && index <= 0x4C) return avrcp_operation_name[index - 0x3B];
142     return avrcp_operation_name[0];
143 }
144 
145 static const char * avrcp_media_attribute_id_name[] = {
146     "NONE", "TITLE", "ARTIST", "ALBUM", "TRACK", "TOTAL TRACKS", "GENRE", "SONG LENGTH"
147 };
148 const char * avrcp_attribute2str(uint8_t index){
149     if (index >= 1 && index <= 7) return avrcp_media_attribute_id_name[index];
150     return avrcp_media_attribute_id_name[0];
151 }
152 
153 static const char * avrcp_play_status_name[] = {
154     "STOPPED", "PLAYING", "PAUSED", "FORWARD SEEK", "REVERSE SEEK",
155     "ERROR" // 0xFF
156 };
157 const char * avrcp_play_status2str(uint8_t index){
158     if (index >= 1 && index <= 4) return avrcp_play_status_name[index];
159     return avrcp_play_status_name[5];
160 }
161 
162 static const char * avrcp_ctype_name[] = {
163     "CONTROL",
164     "STATUS",
165     "SPECIFIC_INQUIRY",
166     "NOTIFY",
167     "GENERAL_INQUIRY",
168     "RESERVED5",
169     "RESERVED6",
170     "RESERVED7",
171     "NOT IMPLEMENTED IN REMOTE",
172     "ACCEPTED BY REMOTE",
173     "REJECTED BY REMOTE",
174     "IN_TRANSITION",
175     "IMPLEMENTED_STABLE",
176     "CHANGED_STABLE",
177     "RESERVED",
178     "INTERIM"
179 };
180 const char * avrcp_ctype2str(uint8_t index){
181     if (index < sizeof(avrcp_ctype_name)){
182         return avrcp_ctype_name[index];
183     }
184     return "NONE";
185 }
186 
187 static const char * avrcp_shuffle_mode_name[] = {
188     "SHUFFLE OFF",
189     "SHUFFLE ALL TRACKS",
190     "SHUFFLE GROUP"
191 };
192 
193 const char * avrcp_shuffle2str(uint8_t index){
194     if (index >= 1 && index <= 3) return avrcp_shuffle_mode_name[index-1];
195     return "NONE";
196 }
197 
198 static const char * avrcp_repeat_mode_name[] = {
199     "REPEAT OFF",
200     "REPEAT SINGLE TRACK",
201     "REPEAT ALL TRACKS",
202     "REPEAT GROUP"
203 };
204 
205 const char * avrcp_repeat2str(uint8_t index){
206     if (index >= 1 && index <= 4) return avrcp_repeat_mode_name[index-1];
207     return "NONE";
208 }
209 static void packet_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size, avrcp_context_t * context);
210 
211 static avrcp_sdp_query_context_t sdp_query_context;
212 static void avrcp_handle_sdp_client_query_result(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size);
213 
214 static void avrcp_create_sdp_record(uint8_t controller, uint8_t * service, uint32_t service_record_handle, uint8_t browsing, uint16_t supported_features, const char * service_name, const char * service_provider_name){
215     uint8_t* attribute;
216     de_create_sequence(service);
217 
218     // 0x0000 "Service Record Handle"
219     de_add_number(service, DE_UINT, DE_SIZE_16, BLUETOOTH_ATTRIBUTE_SERVICE_RECORD_HANDLE);
220     de_add_number(service, DE_UINT, DE_SIZE_32, service_record_handle);
221 
222     // 0x0001 "Service Class ID List"
223     de_add_number(service,  DE_UINT, DE_SIZE_16, BLUETOOTH_ATTRIBUTE_SERVICE_CLASS_ID_LIST);
224     attribute = de_push_sequence(service);
225     {
226         if (controller){
227             de_add_number(attribute, DE_UUID, DE_SIZE_16, BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL);
228             de_add_number(attribute, DE_UUID, DE_SIZE_16, BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL_CONTROLLER);
229         } else {
230             de_add_number(attribute, DE_UUID, DE_SIZE_16, BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL_TARGET);
231         }
232     }
233     de_pop_sequence(service, attribute);
234 
235     // 0x0004 "Protocol Descriptor List"
236     de_add_number(service,  DE_UINT, DE_SIZE_16, BLUETOOTH_ATTRIBUTE_PROTOCOL_DESCRIPTOR_LIST);
237     attribute = de_push_sequence(service);
238     {
239         uint8_t* l2cpProtocol = de_push_sequence(attribute);
240         {
241             de_add_number(l2cpProtocol,  DE_UUID, DE_SIZE_16, BLUETOOTH_PROTOCOL_L2CAP);
242             de_add_number(l2cpProtocol,  DE_UINT, DE_SIZE_16, BLUETOOTH_PROTOCOL_AVCTP);
243         }
244         de_pop_sequence(attribute, l2cpProtocol);
245 
246         uint8_t* avctpProtocol = de_push_sequence(attribute);
247         {
248             de_add_number(avctpProtocol,  DE_UUID, DE_SIZE_16, BLUETOOTH_PROTOCOL_AVCTP);  // avctpProtocol_service
249             de_add_number(avctpProtocol,  DE_UINT, DE_SIZE_16,  0x0103);    // version
250         }
251         de_pop_sequence(attribute, avctpProtocol);
252     }
253     de_pop_sequence(service, attribute);
254 
255     // 0x0005 "Public Browse Group"
256     de_add_number(service,  DE_UINT, DE_SIZE_16, BLUETOOTH_ATTRIBUTE_BROWSE_GROUP_LIST); // public browse group
257     attribute = de_push_sequence(service);
258     {
259         de_add_number(attribute,  DE_UUID, DE_SIZE_16, BLUETOOTH_ATTRIBUTE_PUBLIC_BROWSE_ROOT);
260     }
261     de_pop_sequence(service, attribute);
262 
263     // 0x0009 "Bluetooth Profile Descriptor List"
264     de_add_number(service,  DE_UINT, DE_SIZE_16, BLUETOOTH_ATTRIBUTE_BLUETOOTH_PROFILE_DESCRIPTOR_LIST);
265     attribute = de_push_sequence(service);
266     {
267         uint8_t *avrcProfile = de_push_sequence(attribute);
268         {
269             de_add_number(avrcProfile,  DE_UUID, DE_SIZE_16, BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL);
270             de_add_number(avrcProfile,  DE_UINT, DE_SIZE_16, 0x0105);
271         }
272         de_pop_sequence(attribute, avrcProfile);
273     }
274     de_pop_sequence(service, attribute);
275 
276     // 0x000d "Additional Bluetooth Profile Descriptor List"
277     de_add_number(service,  DE_UINT, DE_SIZE_16, BLUETOOTH_ATTRIBUTE_ADDITIONAL_PROTOCOL_DESCRIPTOR_LISTS);
278     attribute = de_push_sequence(service);
279     if (browsing){
280         uint8_t* browsing_l2cpProtocol = de_push_sequence(attribute);
281         {
282             de_add_number(browsing_l2cpProtocol,  DE_UUID, DE_SIZE_16, BLUETOOTH_PROTOCOL_L2CAP);
283             de_add_number(browsing_l2cpProtocol,  DE_UINT, DE_SIZE_16, PSM_AVCTP_BROWSING);
284         }
285         de_pop_sequence(attribute, browsing_l2cpProtocol);
286 
287         uint8_t* browsing_avctpProtocol = de_push_sequence(attribute);
288         {
289             de_add_number(browsing_avctpProtocol,  DE_UUID, DE_SIZE_16, BLUETOOTH_PROTOCOL_AVCTP);  // browsing_avctpProtocol_service
290             de_add_number(browsing_avctpProtocol,  DE_UINT, DE_SIZE_16,  0x0103);    // version
291         }
292         de_pop_sequence(attribute, browsing_avctpProtocol);
293     }
294     de_pop_sequence(service, attribute);
295 
296 
297     // 0x0100 "Service Name"
298     de_add_number(service,  DE_UINT, DE_SIZE_16, 0x0100);
299     if (service_name){
300         de_add_data(service,  DE_STRING, strlen(service_name), (uint8_t *) service_name);
301     } else {
302         if (controller){
303             de_add_data(service,  DE_STRING, strlen(default_avrcp_controller_service_name), (uint8_t *) default_avrcp_controller_service_name);
304         } else {
305             de_add_data(service,  DE_STRING, strlen(default_avrcp_target_service_name), (uint8_t *) default_avrcp_target_service_name);
306         }
307     }
308 
309     // 0x0100 "Provider Name"
310     de_add_number(service,  DE_UINT, DE_SIZE_16, 0x0102);
311     if (service_provider_name){
312         de_add_data(service,  DE_STRING, strlen(service_provider_name), (uint8_t *) service_provider_name);
313     } else {
314         if (controller){
315             de_add_data(service,  DE_STRING, strlen(default_avrcp_controller_service_provider_name), (uint8_t *) default_avrcp_controller_service_provider_name);
316         } else {
317             de_add_data(service,  DE_STRING, strlen(default_avrcp_target_service_provider_name), (uint8_t *) default_avrcp_target_service_provider_name);
318         }
319     }
320 
321     // 0x0311 "Supported Features"
322     de_add_number(service, DE_UINT, DE_SIZE_16, 0x0311);
323     de_add_number(service, DE_UINT, DE_SIZE_16, supported_features);
324 }
325 
326 void avrcp_controller_create_sdp_record(uint8_t * service, uint32_t service_record_handle, uint8_t browsing, uint16_t supported_features, const char * service_name, const char * service_provider_name){
327     avrcp_create_sdp_record(1, service, service_record_handle, browsing, supported_features, service_name, service_provider_name);
328 }
329 
330 void avrcp_target_create_sdp_record(uint8_t * service, uint32_t service_record_handle, uint8_t browsing, uint16_t supported_features, const char * service_name, const char * service_provider_name){
331     avrcp_create_sdp_record(0, service, service_record_handle, browsing, supported_features, service_name, service_provider_name);
332 }
333 
334 static void avrcp_emit_connection_established(btstack_packet_handler_t callback, uint16_t avrcp_cid, bd_addr_t addr, uint8_t status){
335     if (!callback) return;
336     uint8_t event[12];
337     int pos = 0;
338     event[pos++] = HCI_EVENT_AVRCP_META;
339     event[pos++] = sizeof(event) - 2;
340     event[pos++] = AVRCP_SUBEVENT_CONNECTION_ESTABLISHED;
341     event[pos++] = status;
342     reverse_bd_addr(addr,&event[pos]);
343     pos += 6;
344     little_endian_store_16(event, pos, avrcp_cid);
345     pos += 2;
346     (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
347 }
348 
349 static void avrcp_emit_repeat_and_shuffle_mode(btstack_packet_handler_t callback, uint16_t avrcp_cid, uint8_t ctype, avrcp_repeat_mode_t repeat_mode, avrcp_shuffle_mode_t shuffle_mode){
350     if (!callback) return;
351     uint8_t event[8];
352     int pos = 0;
353     event[pos++] = HCI_EVENT_AVRCP_META;
354     event[pos++] = sizeof(event) - 2;
355     event[pos++] = AVRCP_SUBEVENT_SHUFFLE_AND_REPEAT_MODE;
356     little_endian_store_16(event, pos, avrcp_cid);
357     pos += 2;
358     event[pos++] = ctype;
359     event[pos++] = repeat_mode;
360     event[pos++] = shuffle_mode;
361     (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
362 }
363 
364 static void avrcp_emit_operation_status(btstack_packet_handler_t callback, uint8_t subevent, uint16_t avrcp_cid, uint8_t ctype, uint8_t operation_id){
365     if (!callback) return;
366     uint8_t event[7];
367     int pos = 0;
368     event[pos++] = HCI_EVENT_AVRCP_META;
369     event[pos++] = sizeof(event) - 2;
370     event[pos++] = subevent;
371     little_endian_store_16(event, pos, avrcp_cid);
372     pos += 2;
373     event[pos++] = ctype;
374     event[pos++] = operation_id;
375     (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
376 }
377 
378 static void avrcp_emit_connection_closed(btstack_packet_handler_t callback, uint16_t avrcp_cid){
379     if (!callback) return;
380     uint8_t event[5];
381     int pos = 0;
382     event[pos++] = HCI_EVENT_AVRCP_META;
383     event[pos++] = sizeof(event) - 2;
384     event[pos++] = AVRCP_SUBEVENT_CONNECTION_RELEASED;
385     little_endian_store_16(event, pos, avrcp_cid);
386     pos += 2;
387     (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
388 }
389 
390 static avrcp_connection_t * get_avrcp_connection_for_bd_addr(bd_addr_t addr, avrcp_context_t * context){
391     btstack_linked_list_iterator_t it;
392     btstack_linked_list_iterator_init(&it, (btstack_linked_list_t *) &context->connections);
393     while (btstack_linked_list_iterator_has_next(&it)){
394         avrcp_connection_t * connection = (avrcp_connection_t *)btstack_linked_list_iterator_next(&it);
395         if (memcmp(addr, connection->remote_addr, 6) != 0) continue;
396         return connection;
397     }
398     return NULL;
399 }
400 
401 static avrcp_connection_t * get_avrcp_connection_for_l2cap_signaling_cid(uint16_t l2cap_cid, avrcp_context_t * context){
402     btstack_linked_list_iterator_t it;
403     btstack_linked_list_iterator_init(&it, (btstack_linked_list_t *)  &context->connections);
404     while (btstack_linked_list_iterator_has_next(&it)){
405         avrcp_connection_t * connection = (avrcp_connection_t *)btstack_linked_list_iterator_next(&it);
406         if (connection->l2cap_signaling_cid != l2cap_cid) continue;
407         return connection;
408     }
409     return NULL;
410 }
411 
412 static avrcp_connection_t * get_avrcp_connection_for_avrcp_cid(uint16_t l2cap_cid, avrcp_context_t * context){
413     btstack_linked_list_iterator_t it;
414     btstack_linked_list_iterator_init(&it, (btstack_linked_list_t *)  &context->connections);
415     while (btstack_linked_list_iterator_has_next(&it)){
416         avrcp_connection_t * connection = (avrcp_connection_t *)btstack_linked_list_iterator_next(&it);
417         if (connection->avrcp_cid != l2cap_cid) continue;
418         return connection;
419     }
420     return NULL;
421 }
422 
423 static void avrcp_request_can_send_now(avrcp_connection_t * connection, uint16_t l2cap_cid){
424     connection->wait_to_send = 1;
425     l2cap_request_can_send_now_event(l2cap_cid);
426 }
427 
428 static void avrcp_press_and_hold_timeout_handler(btstack_timer_source_t * timer){
429     UNUSED(timer);
430     avrcp_connection_t * connection = btstack_run_loop_get_timer_context(timer);
431     btstack_run_loop_set_timer(&connection->press_and_hold_cmd_timer, 2000); // 2 seconds timeout
432     btstack_run_loop_add_timer(&connection->press_and_hold_cmd_timer);
433     connection->state = AVCTP_W2_SEND_PRESS_COMMAND;
434     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
435 }
436 
437 static void avrcp_press_and_hold_timer_start(avrcp_connection_t * connection){
438     btstack_run_loop_remove_timer(&connection->press_and_hold_cmd_timer);
439     btstack_run_loop_set_timer_handler(&connection->press_and_hold_cmd_timer, avrcp_press_and_hold_timeout_handler);
440     btstack_run_loop_set_timer_context(&connection->press_and_hold_cmd_timer, connection);
441     btstack_run_loop_set_timer(&connection->press_and_hold_cmd_timer, 2000); // 2 seconds timeout
442     btstack_run_loop_add_timer(&connection->press_and_hold_cmd_timer);
443 }
444 
445 static void avrcp_press_and_hold_timer_stop(avrcp_connection_t * connection){
446     connection->continuous_fast_forward_cmd = 0;
447     btstack_run_loop_remove_timer(&connection->press_and_hold_cmd_timer);
448 }
449 
450 static uint8_t request_pass_through_release_control_cmd(avrcp_connection_t * connection){
451     connection->state = AVCTP_W2_SEND_RELEASE_COMMAND;
452     if (connection->continuous_fast_forward_cmd){
453         avrcp_press_and_hold_timer_stop(connection);
454     }
455     connection->cmd_operands[0] = 0x80 | connection->cmd_operands[0];
456     connection->transaction_label++;
457     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
458     return ERROR_CODE_SUCCESS;
459 }
460 
461 static inline uint8_t request_pass_through_press_control_cmd(uint16_t avrcp_cid, avrcp_operation_id_t opid, uint16_t playback_speed, uint8_t continuous_fast_forward_cmd, avrcp_context_t * context){
462     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, context);
463     if (!connection){
464         log_error("avrcp: could not find a connection.");
465         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
466     }
467     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
468     connection->state = AVCTP_W2_SEND_PRESS_COMMAND;
469     connection->command_opcode =  AVRCP_CMD_OPCODE_PASS_THROUGH;
470     connection->command_type = AVRCP_CTYPE_CONTROL;
471     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
472     connection->subunit_id =   AVRCP_SUBUNIT_ID;
473     connection->cmd_operands_length = 0;
474 
475     connection->continuous_fast_forward_cmd = continuous_fast_forward_cmd;
476     connection->cmd_operands_length = 2;
477     connection->cmd_operands[0] = opid;
478     if (playback_speed > 0){
479         connection->cmd_operands[2] = playback_speed;
480         connection->cmd_operands_length++;
481     }
482     connection->cmd_operands[1] = connection->cmd_operands_length - 2;
483 
484     if (connection->continuous_fast_forward_cmd){
485         avrcp_press_and_hold_timer_start(connection);
486     }
487 
488     connection->transaction_label++;
489     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
490     return ERROR_CODE_SUCCESS;
491 }
492 
493 static uint8_t request_single_pass_through_press_control_cmd(uint16_t avrcp_cid, avrcp_operation_id_t opid, uint16_t playback_speed){
494     return request_pass_through_press_control_cmd(avrcp_cid, opid, playback_speed, 0, &avrcp_controller_context);
495 }
496 
497 static uint8_t request_continuous_pass_through_press_control_cmd(uint16_t avrcp_cid, avrcp_operation_id_t opid, uint16_t playback_speed){
498     return request_pass_through_press_control_cmd(avrcp_cid, opid, playback_speed, 1, &avrcp_controller_context);
499 }
500 
501 static int avrcp_send_cmd(uint16_t cid, avrcp_connection_t * connection){
502     uint8_t command[30];
503     int pos = 0;
504     // transport header
505     // Transaction label | Packet_type | C/R | IPID (1 == invalid profile identifier)
506     command[pos++] = (connection->transaction_label << 4) | (AVRCP_SINGLE_PACKET << 2) | (AVRCP_COMMAND_FRAME << 1) | 0;
507     // Profile IDentifier (PID)
508     command[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL >> 8;
509     command[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL & 0x00FF;
510 
511     // command_type
512     command[pos++] = connection->command_type;
513     // subunit_type | subunit ID
514     command[pos++] = (connection->subunit_type << 3) | connection->subunit_id;
515     // opcode
516     command[pos++] = (uint8_t)connection->command_opcode;
517     // operands
518     memcpy(command+pos, connection->cmd_operands, connection->cmd_operands_length);
519     pos += connection->cmd_operands_length;
520 
521     return l2cap_send(cid, command, pos);
522 }
523 
524 static int avrcp_register_notification(avrcp_connection_t * connection, avrcp_notification_event_id_t event_id){
525     if (connection->notifications_to_deregister & (1 << event_id)) return 0;
526     if (connection->notifications_enabled & (1 << event_id)) return 0;
527     if (connection->notifications_to_register & (1 << event_id)) return 0;
528     connection->notifications_to_register |= (1 << event_id);
529     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
530     return 1;
531 }
532 
533 static void avrcp_prepare_notification(avrcp_connection_t * connection, avrcp_notification_event_id_t event_id){
534     connection->transaction_label++;
535     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
536     connection->command_type = AVRCP_CTYPE_NOTIFY;
537     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
538     connection->subunit_id = AVRCP_SUBUNIT_ID;
539     int pos = 0;
540     big_endian_store_24(connection->cmd_operands, pos, BT_SIG_COMPANY_ID);
541     pos += 3;
542     connection->cmd_operands[pos++] = AVRCP_PDU_ID_REGISTER_NOTIFICATION;
543     connection->cmd_operands[pos++] = 0;                     // reserved(upper 6) | packet_type -> 0
544     big_endian_store_16(connection->cmd_operands, pos, 5);     // parameter length
545     pos += 2;
546     connection->cmd_operands[pos++] = event_id;
547     big_endian_store_32(connection->cmd_operands, pos, 0);
548     pos += 4;
549     connection->cmd_operands_length = pos;
550     // AVRCP_SPEC_V14.pdf 166
551     // answer page 61
552 }
553 
554 static uint8_t avrcp_cmd_opcode(uint8_t *packet, uint16_t size){
555     uint8_t cmd_opcode_index = 5;
556     if (cmd_opcode_index > size) return AVRCP_CMD_OPCODE_UNDEFINED;
557     return packet[cmd_opcode_index];
558 }
559 
560 static void avrcp_handle_sdp_client_query_result(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
561     if (!sdp_query_context.connection) return;
562     if (sdp_query_context.connection->state != AVCTP_SIGNALING_W4_SDP_QUERY_COMPLETE) return;
563     UNUSED(packet_type);
564     UNUSED(channel);
565     UNUSED(size);
566 
567     des_iterator_t des_list_it;
568     des_iterator_t prot_it;
569     // uint32_t avdtp_remote_uuid    = 0;
570 
571     switch (hci_event_packet_get_type(packet)){
572         case SDP_EVENT_QUERY_ATTRIBUTE_VALUE:
573             // Handle new SDP record
574             if (sdp_event_query_attribute_byte_get_record_id(packet) != record_id) {
575                 record_id = sdp_event_query_attribute_byte_get_record_id(packet);
576                 // log_info("SDP Record: Nr: %d", record_id);
577             }
578 
579             if (sdp_event_query_attribute_byte_get_attribute_length(packet) <= attribute_value_buffer_size) {
580                 attribute_value[sdp_event_query_attribute_byte_get_data_offset(packet)] = sdp_event_query_attribute_byte_get_data(packet);
581 
582                 if ((uint16_t)(sdp_event_query_attribute_byte_get_data_offset(packet)+1) == sdp_event_query_attribute_byte_get_attribute_length(packet)) {
583                     switch(sdp_event_query_attribute_byte_get_attribute_id(packet)) {
584                         case BLUETOOTH_ATTRIBUTE_SERVICE_CLASS_ID_LIST:
585                             if (de_get_element_type(attribute_value) != DE_DES) break;
586                             for (des_iterator_init(&des_list_it, attribute_value); des_iterator_has_more(&des_list_it); des_iterator_next(&des_list_it)) {
587                                 uint8_t * element = des_iterator_get_element(&des_list_it);
588                                 if (de_get_element_type(element) != DE_UUID) continue;
589                                 uint32_t uuid = de_get_uuid32(element);
590                                 switch (uuid){
591                                     case BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL_TARGET:
592                                         if (sdp_query_context.avrcp_context->role == AVRCP_TARGET) {
593                                             sdp_query_context.role_supported = 1;
594                                             break;
595                                         }
596                                         break;
597                                     case BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL:
598                                     case BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL_CONTROLLER:
599                                         if (sdp_query_context.avrcp_context->role == AVRCP_CONTROLLER) {
600                                             sdp_query_context.role_supported = 1;
601                                             break;
602                                         }
603                                         break;
604                                     default:
605                                         break;
606                                 }
607                             }
608                             break;
609 
610                         case BLUETOOTH_ATTRIBUTE_PROTOCOL_DESCRIPTOR_LIST: {
611                                 // log_info("SDP Attribute: 0x%04x", sdp_event_query_attribute_byte_get_attribute_id(packet));
612                                 for (des_iterator_init(&des_list_it, attribute_value); des_iterator_has_more(&des_list_it); des_iterator_next(&des_list_it)) {
613                                     uint8_t       *des_element;
614                                     uint8_t       *element;
615                                     uint32_t       uuid;
616 
617                                     if (des_iterator_get_type(&des_list_it) != DE_DES) continue;
618 
619                                     des_element = des_iterator_get_element(&des_list_it);
620                                     des_iterator_init(&prot_it, des_element);
621                                     element = des_iterator_get_element(&prot_it);
622 
623                                     if (de_get_element_type(element) != DE_UUID) continue;
624 
625                                     uuid = de_get_uuid32(element);
626                                     switch (uuid){
627                                         case BLUETOOTH_PROTOCOL_L2CAP:
628                                             if (!des_iterator_has_more(&prot_it)) continue;
629                                             des_iterator_next(&prot_it);
630                                             de_element_get_uint16(des_iterator_get_element(&prot_it), &sdp_query_context.avrcp_l2cap_psm);
631                                             break;
632                                         case BLUETOOTH_PROTOCOL_AVCTP:
633                                             if (!des_iterator_has_more(&prot_it)) continue;
634                                             des_iterator_next(&prot_it);
635                                             de_element_get_uint16(des_iterator_get_element(&prot_it), &sdp_query_context.avrcp_version);
636                                             break;
637                                         default:
638                                             break;
639                                     }
640                                 }
641                             }
642                             break;
643                         case BLUETOOTH_ATTRIBUTE_ADDITIONAL_PROTOCOL_DESCRIPTOR_LISTS: {
644                                 // log_info("SDP Attribute: 0x%04x", sdp_event_query_attribute_byte_get_attribute_id(packet));
645                                 if (de_get_element_type(attribute_value) != DE_DES) break;
646 
647                                 des_iterator_t des_list_0_it;
648                                 uint8_t       *element_0;
649 
650                                 des_iterator_init(&des_list_0_it, attribute_value);
651                                 element_0 = des_iterator_get_element(&des_list_0_it);
652 
653                                 for (des_iterator_init(&des_list_it, element_0); des_iterator_has_more(&des_list_it); des_iterator_next(&des_list_it)) {
654                                     uint8_t       *des_element;
655                                     uint8_t       *element;
656                                     uint32_t       uuid;
657 
658                                     if (des_iterator_get_type(&des_list_it) != DE_DES) continue;
659 
660                                     des_element = des_iterator_get_element(&des_list_it);
661                                     des_iterator_init(&prot_it, des_element);
662                                     element = des_iterator_get_element(&prot_it);
663 
664                                     if (de_get_element_type(element) != DE_UUID) continue;
665 
666                                     uuid = de_get_uuid32(element);
667                                     switch (uuid){
668                                         case BLUETOOTH_PROTOCOL_L2CAP:
669                                             if (!des_iterator_has_more(&prot_it)) continue;
670                                             des_iterator_next(&prot_it);
671                                             de_element_get_uint16(des_iterator_get_element(&prot_it), &sdp_query_context.avrcp_browsing_l2cap_psm);
672                                             break;
673                                         case BLUETOOTH_PROTOCOL_AVCTP:
674                                             if (!des_iterator_has_more(&prot_it)) continue;
675                                             des_iterator_next(&prot_it);
676                                             de_element_get_uint16(des_iterator_get_element(&prot_it), &sdp_query_context.avrcp_browsing_version);
677                                             break;
678                                         default:
679                                             break;
680                                     }
681                                 }
682                             }
683                             break;
684                         default:
685                             break;
686                     }
687                 }
688             } else {
689                 log_error("SDP attribute value buffer size exceeded: available %d, required %d", attribute_value_buffer_size, sdp_event_query_attribute_byte_get_attribute_length(packet));
690             }
691             break;
692 
693         case SDP_EVENT_QUERY_COMPLETE:
694             log_info("General query done with status %d.", sdp_event_query_complete_get_status(packet));
695             if (!sdp_query_context.role_supported || !sdp_query_context.avrcp_l2cap_psm){
696                 sdp_query_context.connection->state = AVCTP_CONNECTION_IDLE;
697                 avrcp_emit_connection_established(sdp_query_context.avrcp_context->avrcp_callback, sdp_query_context.connection->avrcp_cid, sdp_query_context.connection->remote_addr, SDP_SERVICE_NOT_FOUND);
698                 break;
699             }
700             log_info("AVRCP Control PSM 0x%02x, Browsing PSM 0x%02x", sdp_query_context.avrcp_l2cap_psm, sdp_query_context.avrcp_browsing_l2cap_psm);
701 
702             sdp_query_context.connection->state = AVCTP_CONNECTION_W4_L2CAP_CONNECTED;
703             l2cap_create_channel(sdp_query_context.avrcp_context->packet_handler, sdp_query_context.connection->remote_addr, sdp_query_context.avrcp_l2cap_psm, l2cap_max_mtu(), NULL);
704             break;
705     }
706 }
707 
708 static void avrcp_handle_l2cap_data_packet_for_signaling_connection(avrcp_connection_t * connection, uint8_t *packet, uint16_t size){
709     uint8_t operands[20];
710     uint8_t opcode;
711     int     pos = 3;
712     // uint8_t transport_header = packet[0];
713     // uint8_t transaction_label = transport_header >> 4;
714     // uint8_t packet_type = (transport_header & 0x0F) >> 2;
715     // uint8_t frame_type = (transport_header & 0x03) >> 1;
716     // uint8_t ipid = transport_header & 0x01;
717     // uint8_t byte_value = packet[2];
718     // uint16_t pid = (byte_value << 8) | packet[2];
719 
720     avrcp_command_type_t ctype = (avrcp_command_type_t) packet[pos++];
721     uint8_t byte_value = packet[pos++];
722     avrcp_subunit_type_t subunit_type = (avrcp_subunit_type_t) (byte_value >> 3);
723     avrcp_subunit_type_t subunit_id = (avrcp_subunit_type_t)   (byte_value & 0x07);
724     opcode = packet[pos++];
725 
726     // printf("    Transport header 0x%02x (transaction_label %d, packet_type %d, frame_type %d, ipid %d), pid 0x%4x\n",
727     //     transport_header, transaction_label, packet_type, frame_type, ipid, pid);
728     // // printf_hexdump(packet+pos, size-pos);
729 
730     uint8_t pdu_id;
731     uint16_t param_length;
732     switch (avrcp_cmd_opcode(packet,size)){
733         case AVRCP_CMD_OPCODE_UNIT_INFO:{
734             if (connection->state != AVCTP_W2_RECEIVE_RESPONSE) return;
735             connection->state = AVCTP_CONNECTION_OPENED;
736 
737             // operands:
738             memcpy(operands, packet+pos, 5);
739             uint8_t unit_type = operands[1] >> 3;
740             uint8_t unit = operands[1] & 0x07;
741             uint32_t company_id = operands[2] << 16 | operands[3] << 8 | operands[4];
742             log_info("    UNIT INFO response: ctype 0x%02x (0C), subunit_type 0x%02x (1F), subunit_id 0x%02x (07), opcode 0x%02x (30), unit_type 0x%02x, unit %d, company_id 0x%06x",
743                 ctype, subunit_type, subunit_id, opcode, unit_type, unit, company_id );
744             break;
745         }
746         case AVRCP_CMD_OPCODE_VENDOR_DEPENDENT:
747             if (size - pos < 7) {
748                 log_error("avrcp: wrong packet size");
749                 return;
750             };
751             // operands:
752             memcpy(operands, packet+pos, 7);
753             pos += 7;
754             // uint32_t company_id = operands[0] << 16 | operands[1] << 8 | operands[2];
755             pdu_id = operands[3];
756 
757             if (connection->state != AVCTP_W2_RECEIVE_RESPONSE && pdu_id != AVRCP_PDU_ID_REGISTER_NOTIFICATION){
758                 log_info("AVRCP_CMD_OPCODE_VENDOR_DEPENDENT state %d", connection->state);
759                 return;
760             }
761             connection->state = AVCTP_CONNECTION_OPENED;
762 
763 
764             // uint8_t unit_type = operands[4] >> 3;
765             // uint8_t unit = operands[4] & 0x07;
766             param_length = big_endian_read_16(operands, 5);
767 
768             // printf("    VENDOR DEPENDENT response: ctype 0x%02x (0C), subunit_type 0x%02x (1F), subunit_id 0x%02x (07), opcode 0x%02x (30), unit_type 0x%02x, unit %d, company_id 0x%06x\n",
769             //     ctype, subunit_type, subunit_id, opcode, unit_type, unit, company_id );
770 
771             // if (ctype == AVRCP_CTYPE_RESPONSE_INTERIM) return;
772             log_info("        VENDOR DEPENDENT response: pdu id 0x%02x, param_length %d, status %s", pdu_id, param_length, avrcp_ctype2str(ctype));
773             switch (pdu_id){
774                 case AVRCP_PDU_ID_GetCurrentPlayerApplicationSettingValue:{
775                     uint8_t num_attributes = packet[pos++];
776                     int i;
777                     avrcp_repeat_mode_t  repeat_mode =  AVRCP_REPEAT_MODE_INVALID;
778                     avrcp_shuffle_mode_t shuffle_mode = AVRCP_SHUFFLE_MODE_INVALID;
779                     for (i = 0; i < num_attributes; i++){
780                         uint8_t attribute_id    = packet[pos++];
781                         uint8_t value = packet[pos++];
782                         switch (attribute_id){
783                             case 0x02:
784                                 repeat_mode = (avrcp_repeat_mode_t) value;
785                                 break;
786                             case 0x03:
787                                 shuffle_mode = (avrcp_shuffle_mode_t) value;
788                                 break;
789                             default:
790                                 break;
791                         }
792                     }
793                     avrcp_emit_repeat_and_shuffle_mode(avrcp_callback, connection->avrcp_cid, ctype, repeat_mode, shuffle_mode);
794                     break;
795                 }
796                 case AVRCP_PDU_ID_SetPlayerApplicationSettingValue:{
797                     uint8_t event[6];
798                     int offset = 0;
799                     event[offset++] = HCI_EVENT_AVRCP_META;
800                     event[offset++] = sizeof(event) - 2;
801                     event[offset++] = AVRCP_SUBEVENT_PLAYER_APPLICATION_VALUE_RESPONSE;
802                     little_endian_store_16(event, offset, connection->avrcp_cid);
803                     offset += 2;
804                     event[offset++] = ctype;
805                     (*avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
806                     break;
807                 }
808                 case AVRCP_PDU_ID_SET_ABSOLUTE_VOLUME:{
809                     uint8_t event[7];
810                     int offset = 0;
811                     event[offset++] = HCI_EVENT_AVRCP_META;
812                     event[offset++] = sizeof(event) - 2;
813                     event[offset++] = AVRCP_SUBEVENT_SET_ABSOLUTE_VOLUME_RESPONSE;
814                     little_endian_store_16(event, offset, connection->avrcp_cid);
815                     offset += 2;
816                     event[offset++] = ctype;
817                     event[offset++] = packet[pos++];
818                     (*avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
819                     break;
820                 }
821                 case AVRCP_PDU_ID_GET_CAPABILITIES:{
822                     avrcp_capability_id_t capability_id = (avrcp_capability_id_t) packet[pos++];
823                     uint8_t capability_count = packet[pos++];
824                     int i;
825                     switch (capability_id){
826                         case AVRCP_CAPABILITY_ID_COMPANY:
827                             // log_info("Supported companies %d: ", capability_count);
828                             for (i = 0; i < capability_count; i++){
829                                 uint32_t company_id = big_endian_read_24(packet, pos);
830                                 pos += 3;
831                                 log_info("  0x%06x, ", company_id);
832                             }
833                             break;
834                         case AVRCP_CAPABILITY_ID_EVENT:
835                             // log_info("Supported events %d: ", capability_count);
836                             for (i = 0; i < capability_count; i++){
837                                 uint8_t event_id = packet[pos++];
838                                 log_info("  0x%02x %s", event_id, avrcp_event2str(event_id));
839                             }
840                             break;
841                     }
842                     break;
843                 }
844                 case AVRCP_PDU_ID_GET_PLAY_STATUS:{
845                     uint32_t song_length = big_endian_read_32(packet, pos);
846                     pos += 4;
847                     uint32_t song_position = big_endian_read_32(packet, pos);
848                     pos += 4;
849                     uint8_t play_status = packet[pos];
850                     // log_info("        GET_PLAY_STATUS length 0x%04X, position 0x%04X, status %s", song_length, song_position, avrcp_play_status2str(play_status));
851 
852                     uint8_t event[15];
853                     int offset = 0;
854                     event[offset++] = HCI_EVENT_AVRCP_META;
855                     event[offset++] = sizeof(event) - 2;
856                     event[offset++] = AVRCP_SUBEVENT_PLAY_STATUS;
857                     little_endian_store_16(event, offset, connection->avrcp_cid);
858                     offset += 2;
859                     event[offset++] = ctype;
860                     little_endian_store_32(event, offset, song_length);
861                     offset += 4;
862                     little_endian_store_32(event, offset, song_position);
863                     offset += 4;
864                     event[offset++] = play_status;
865                     (*avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
866                     break;
867                 }
868                 case AVRCP_PDU_ID_REGISTER_NOTIFICATION:{
869                     avrcp_notification_event_id_t  event_id = (avrcp_notification_event_id_t) packet[pos++];
870                     uint16_t event_mask = (1 << event_id);
871                     uint16_t reset_event_mask = ~event_mask;
872                     switch (ctype){
873                         case AVRCP_CTYPE_RESPONSE_INTERIM:
874                             // register as enabled
875                             connection->notifications_enabled |= event_mask;
876                             // printf("INTERIM notifications_enabled 0x%2x, notifications_to_register 0x%2x\n", connection->notifications_enabled,  connection->notifications_to_register);
877                             break;
878                         case AVRCP_CTYPE_RESPONSE_CHANGED_STABLE:
879                             // received change, event is considered deregistered
880                             // we are re-enabling it automatically, if it is not
881                             // explicitly disabled
882                             connection->notifications_enabled &= reset_event_mask;
883                             if (! (connection->notifications_to_deregister & event_mask)){
884                                 avrcp_register_notification(connection, event_id);
885                                 // printf("CHANGED_STABLE notifications_enabled 0x%2x, notifications_to_register 0x%2x\n", connection->notifications_enabled,  connection->notifications_to_register);
886                             } else {
887                                 connection->notifications_to_deregister &= reset_event_mask;
888                             }
889                             break;
890                         default:
891                             connection->notifications_to_register &= reset_event_mask;
892                             connection->notifications_enabled &= reset_event_mask;
893                             connection->notifications_to_deregister &= reset_event_mask;
894                             break;
895                     }
896 
897                     switch (event_id){
898                         case AVRCP_NOTIFICATION_EVENT_PLAYBACK_STATUS_CHANGED:{
899                             uint8_t event[7];
900                             int offset = 0;
901                             event[offset++] = HCI_EVENT_AVRCP_META;
902                             event[offset++] = sizeof(event) - 2;
903                             event[offset++] = AVRCP_SUBEVENT_NOTIFICATION_PLAYBACK_STATUS_CHANGED;
904                             little_endian_store_16(event, offset, connection->avrcp_cid);
905                             offset += 2;
906                             event[offset++] = ctype;
907                             event[offset++] = packet[pos];
908                             (*avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
909                             break;
910                         }
911                         case AVRCP_NOTIFICATION_EVENT_TRACK_CHANGED:{
912                             uint8_t event[6];
913                             int offset = 0;
914                             event[offset++] = HCI_EVENT_AVRCP_META;
915                             event[offset++] = sizeof(event) - 2;
916                             event[offset++] = AVRCP_SUBEVENT_NOTIFICATION_TRACK_CHANGED;
917                             little_endian_store_16(event, offset, connection->avrcp_cid);
918                             offset += 2;
919                             event[offset++] = ctype;
920                             (*avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
921                             break;
922                         }
923                         case AVRCP_NOTIFICATION_EVENT_NOW_PLAYING_CONTENT_CHANGED:{
924                             uint8_t event[6];
925                             int offset = 0;
926                             event[offset++] = HCI_EVENT_AVRCP_META;
927                             event[offset++] = sizeof(event) - 2;
928                             event[offset++] = AVRCP_SUBEVENT_NOTIFICATION_NOW_PLAYING_CONTENT_CHANGED;
929                             little_endian_store_16(event, offset, connection->avrcp_cid);
930                             offset += 2;
931                             event[offset++] = ctype;
932                             (*avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
933                             break;
934                         }
935                         case AVRCP_NOTIFICATION_EVENT_AVAILABLE_PLAYERS_CHANGED:{
936                             uint8_t event[6];
937                             int offset = 0;
938                             event[offset++] = HCI_EVENT_AVRCP_META;
939                             event[offset++] = sizeof(event) - 2;
940                             event[offset++] = AVRCP_SUBEVENT_NOTIFICATION_AVAILABLE_PLAYERS_CHANGED;
941                             little_endian_store_16(event, offset, connection->avrcp_cid);
942                             offset += 2;
943                             event[offset++] = ctype;
944                             (*avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
945                             break;
946                         }
947                         case AVRCP_NOTIFICATION_EVENT_VOLUME_CHANGED:{
948                             uint8_t event[7];
949                             int offset = 0;
950                             event[offset++] = HCI_EVENT_AVRCP_META;
951                             event[offset++] = sizeof(event) - 2;
952                             event[offset++] = AVRCP_SUBEVENT_NOTIFICATION_VOLUME_CHANGED;
953                             little_endian_store_16(event, offset, connection->avrcp_cid);
954                             offset += 2;
955                             event[offset++] = ctype;
956                             event[offset++] = packet[pos++] & 0x7F;
957                             (*avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
958                             break;
959                         }
960                         // case AVRCP_NOTIFICATION_EVENT_PLAYER_APPLICATION_SETTING_CHANGED:{
961                         //     uint8_t num_PlayerApplicationSettingAttributes = packet[pos++];
962                         //     int i;
963                         //     for (i = 0; i < num_PlayerApplicationSettingAttributes; i++){
964                         //         uint8_t PlayerApplicationSetting_AttributeID = packet[pos++];
965                         //         uint8_t PlayerApplicationSettingValueID = packet[pos++];
966                         //     }
967                         //     break;
968                         // }
969                         // case AVRCP_NOTIFICATION_EVENT_ADDRESSED_PLAYER_CHANGED:
970                         //     uint16_t player_id = big_endian_read_16(packet, pos);
971                         //     pos += 2;
972                         //     uint16_t uid_counter = big_endian_read_16(packet, pos);
973                         //     pos += 2;
974                         //     break;
975                         // case AVRCP_NOTIFICATION_EVENT_UIDS_CHANGED:
976                         //     uint16_t uid_counter = big_endian_read_16(packet, pos);
977                         //     pos += 2;
978                         //     break;
979                         default:
980                             log_info("avrcp: not implemented");
981                             break;
982                     }
983                     if (connection->notifications_to_register != 0){
984                         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
985                     }
986                     break;
987                 }
988 
989                 case AVRCP_PDU_ID_GET_ELEMENT_ATTRIBUTES:{
990                     uint8_t num_attributes = packet[pos++];
991                     int i;
992                     struct item {
993                         uint16_t len;
994                         uint8_t  * value;
995                     } items[AVRCP_MEDIA_ATTR_COUNT];
996                     memset(items, 0, sizeof(items));
997 
998                     uint16_t string_attributes_len = 0;
999                     uint8_t  num_string_attributes = 0;
1000                     uint16_t total_event_payload_for_string_attributes = HCI_EVENT_PAYLOAD_SIZE-2;
1001                     uint16_t max_string_attribute_value_len = 0;
1002                     if (ctype == AVRCP_CTYPE_RESPONSE_IMPLEMENTED_STABLE || ctype == AVRCP_CTYPE_RESPONSE_CHANGED_STABLE){
1003                         for (i = 0; i < num_attributes; i++){
1004                             avrcp_media_attribute_id_t attr_id = (avrcp_media_attribute_id_t) big_endian_read_32(packet, pos);
1005                             pos += 4;
1006                             // uint16_t character_set = big_endian_read_16(packet, pos);
1007                             pos += 2;
1008                             uint16_t attr_value_length = big_endian_read_16(packet, pos);
1009                             pos += 2;
1010 
1011                             // debug - to remove later
1012                             uint8_t  value[100];
1013                             uint16_t value_len = sizeof(value) <= attr_value_length? sizeof(value) - 1 : attr_value_length;
1014                             memcpy(value, packet+pos, value_len);
1015                             value[value_len] = 0;
1016                             // printf("Now Playing Info %s: %s \n", attribute2str(attr_id), value);
1017                             // end debug
1018 
1019                             if ((attr_id >= 1) || (attr_id <= AVRCP_MEDIA_ATTR_COUNT)) {
1020                                 items[attr_id-1].len = attr_value_length;
1021                                 items[attr_id-1].value = &packet[pos];
1022                                 switch (attr_id){
1023                                     case AVRCP_MEDIA_ATTR_TITLE:
1024                                     case AVRCP_MEDIA_ATTR_ARTIST:
1025                                     case AVRCP_MEDIA_ATTR_ALBUM:
1026                                     case AVRCP_MEDIA_ATTR_GENRE:
1027                                         num_string_attributes++;
1028                                         string_attributes_len += attr_value_length;
1029                                         if (max_string_attribute_value_len < attr_value_length){
1030                                             max_string_attribute_value_len = attr_value_length;
1031                                         }
1032                                         break;
1033                                     default:
1034                                         break;
1035                                 }
1036                             }
1037                             pos += attr_value_length;
1038                         }
1039                     }
1040 
1041                     // subtract space for fixed fields
1042                     total_event_payload_for_string_attributes -= 14 + 4;    // 4 for '\0'
1043 
1044                     // @TODO optimize space by repeatedly decreasing max_string_attribute_value_len until it fits into buffer instead of crude divion
1045                     uint16_t max_value_len = total_event_payload_for_string_attributes > string_attributes_len? max_string_attribute_value_len : total_event_payload_for_string_attributes/(string_attributes_len+1) - 1;
1046                     // printf("num_string_attributes %d, string_attributes_len %d, total_event_payload_for_string_attributes %d, max_value_len %d \n", num_string_attributes, string_attributes_len, total_event_payload_for_string_attributes, max_value_len);
1047 
1048                     const uint8_t attribute_order[] = {
1049                         AVRCP_MEDIA_ATTR_TRACK,
1050                         AVRCP_MEDIA_ATTR_TOTAL_TRACKS,
1051                         AVRCP_MEDIA_ATTR_SONG_LENGTH,
1052                         AVRCP_MEDIA_ATTR_TITLE,
1053                         AVRCP_MEDIA_ATTR_ARTIST,
1054                         AVRCP_MEDIA_ATTR_ALBUM,
1055                         AVRCP_MEDIA_ATTR_GENRE
1056                     };
1057 
1058                     uint8_t event[HCI_EVENT_BUFFER_SIZE];
1059                     event[0] = HCI_EVENT_AVRCP_META;
1060                     pos = 2;
1061                     event[pos++] = AVRCP_SUBEVENT_NOW_PLAYING_INFO;
1062                     little_endian_store_16(event, pos, connection->avrcp_cid);
1063                     pos += 2;
1064                     event[pos++] = ctype;
1065                     for (i = 0; i < sizeof(attribute_order); i++){
1066                         avrcp_media_attribute_id_t attr_id = (avrcp_media_attribute_id_t) attribute_order[i];
1067                         uint16_t value_len = 0;
1068                         switch (attr_id){
1069                             case AVRCP_MEDIA_ATTR_TITLE:
1070                             case AVRCP_MEDIA_ATTR_ARTIST:
1071                             case AVRCP_MEDIA_ATTR_ALBUM:
1072                             case AVRCP_MEDIA_ATTR_GENRE:
1073                                 if (items[attr_id-1].value){
1074                                     value_len = items[attr_id-1].len <= max_value_len ? items[attr_id-1].len : max_value_len;
1075                                 }
1076                                 event[pos++] = value_len + 1;
1077                                 if (value_len){
1078                                     memcpy(event+pos, items[attr_id-1].value, value_len);
1079                                     pos += value_len;
1080                                 }
1081                                 event[pos++] = 0;
1082                                 break;
1083                             case AVRCP_MEDIA_ATTR_SONG_LENGTH:
1084                                 if (items[attr_id-1].value){
1085                                     little_endian_store_32(event, pos, btstack_atoi((char *)items[attr_id-1].value));
1086                                 } else {
1087                                     little_endian_store_32(event, pos, 0);
1088                                 }
1089                                 pos += 4;
1090                                 break;
1091                             case AVRCP_MEDIA_ATTR_TRACK:
1092                             case AVRCP_MEDIA_ATTR_TOTAL_TRACKS:
1093                                 if (items[attr_id-1].value){
1094                                     event[pos++] = btstack_atoi((char *)items[attr_id-1].value);
1095                                 } else {
1096                                     event[pos++] = 0;
1097                                 }
1098                                 break;
1099                         }
1100                     }
1101                     event[1] = pos - 2;
1102                     // printf_hexdump(event, pos);
1103                     (*avrcp_callback)(HCI_EVENT_PACKET, 0, event, pos);
1104                     break;
1105                 }
1106                 default:
1107                     break;
1108             }
1109             break;
1110         case AVRCP_CMD_OPCODE_PASS_THROUGH:{
1111             // 0x80 | connection->cmd_operands[0]
1112             uint8_t operation_id = packet[pos++];
1113             switch (connection->state){
1114                 case AVCTP_W2_RECEIVE_PRESS_RESPONSE:
1115                     if (connection->continuous_fast_forward_cmd){
1116                         connection->state = AVCTP_W4_STOP;
1117                     } else {
1118                         connection->state = AVCTP_W2_SEND_RELEASE_COMMAND;
1119                     }
1120                     break;
1121                 case AVCTP_W2_RECEIVE_RESPONSE:
1122                     connection->state = AVCTP_CONNECTION_OPENED;
1123                     break;
1124                 default:
1125                     // check for notifications? move state transition down
1126                     // log_info("AVRCP_CMD_OPCODE_PASS_THROUGH state %d\n", connection->state);
1127                     break;
1128             }
1129             if (connection->state == AVCTP_W4_STOP){
1130                 avrcp_emit_operation_status(avrcp_callback, AVRCP_SUBEVENT_OPERATION_START, connection->avrcp_cid, ctype, operation_id);
1131             }
1132             if (connection->state == AVCTP_CONNECTION_OPENED) {
1133                 // RELEASE response
1134                 operation_id = operation_id & 0x7F;
1135                 avrcp_emit_operation_status(avrcp_callback, AVRCP_SUBEVENT_OPERATION_COMPLETE, connection->avrcp_cid, ctype, operation_id);
1136             }
1137             if (connection->state == AVCTP_W2_SEND_RELEASE_COMMAND){
1138                 // PRESS response
1139                 request_pass_through_release_control_cmd(connection);
1140             }
1141             break;
1142         }
1143         default:
1144             break;
1145     }
1146 }
1147 
1148 static void avrcp_handle_can_send_now(avrcp_connection_t * connection){
1149     int i;
1150     switch (connection->state){
1151         case AVCTP_W2_SEND_PRESS_COMMAND:
1152             connection->state = AVCTP_W2_RECEIVE_PRESS_RESPONSE;
1153             avrcp_send_cmd(connection->l2cap_signaling_cid, connection);
1154             break;
1155         case AVCTP_W2_SEND_COMMAND:
1156         case AVCTP_W2_SEND_RELEASE_COMMAND:
1157             connection->state = AVCTP_W2_RECEIVE_RESPONSE;
1158             avrcp_send_cmd(connection->l2cap_signaling_cid, connection);
1159             break;
1160         case AVCTP_CONNECTION_OPENED:
1161             if (connection->notifications_to_register != 0){
1162                 for (i = 1; i <= AVRCP_NOTIFICATION_EVENT_VOLUME_CHANGED; i++){
1163                     if (connection->notifications_to_register & (1<<i)){
1164                         connection->notifications_to_register &= ~ (1 << i);
1165                         avrcp_prepare_notification(connection, (avrcp_notification_event_id_t) i);
1166                         connection->state = AVCTP_W2_RECEIVE_RESPONSE;
1167                         avrcp_send_cmd(connection->l2cap_signaling_cid, connection);
1168                         return;
1169                     }
1170                 }
1171             }
1172             return;
1173         default:
1174             return;
1175     }
1176 }
1177 
1178 static avrcp_connection_t * avrcp_create_connection(bd_addr_t remote_addr, avrcp_context_t * context){
1179     avrcp_connection_t * connection = btstack_memory_avrcp_connection_get();
1180     memset(connection, 0, sizeof(avrcp_connection_t));
1181     connection->state = AVCTP_CONNECTION_IDLE;
1182     connection->transaction_label = 0xFF;
1183     memcpy(connection->remote_addr, remote_addr, 6);
1184     btstack_linked_list_add(&context->connections, (btstack_linked_item_t *) connection);
1185     return connection;
1186 }
1187 
1188 static void packet_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size, avrcp_context_t * context){
1189     bd_addr_t event_addr;
1190     uint16_t local_cid;
1191     avrcp_connection_t * connection = NULL;
1192 
1193     switch (packet_type) {
1194         case L2CAP_DATA_PACKET:
1195             connection = get_avrcp_connection_for_l2cap_signaling_cid(channel, context);
1196             if (!connection) break;
1197             avrcp_handle_l2cap_data_packet_for_signaling_connection(connection, packet, size);
1198             break;
1199 
1200         case HCI_EVENT_PACKET:
1201             switch (hci_event_packet_get_type(packet)) {
1202                 case L2CAP_EVENT_INCOMING_CONNECTION:
1203                     l2cap_event_incoming_connection_get_address(packet, event_addr);
1204                     local_cid = l2cap_event_incoming_connection_get_local_cid(packet);
1205                     connection = avrcp_create_connection(event_addr, context);
1206                     if (!connection) {
1207                         log_error("Failed to alloc connection structure");
1208                         l2cap_decline_connection(local_cid);
1209                         break;
1210                     }
1211                     connection->state = AVCTP_CONNECTION_W4_L2CAP_CONNECTED;
1212                     connection->l2cap_signaling_cid = local_cid;
1213                     l2cap_accept_connection(local_cid);
1214                     break;
1215 
1216                 case L2CAP_EVENT_CHANNEL_OPENED:
1217                     l2cap_event_channel_opened_get_address(packet, event_addr);
1218 
1219                     connection = get_avrcp_connection_for_bd_addr(event_addr, context);
1220                     local_cid  = l2cap_event_channel_opened_get_local_cid(packet);
1221 
1222                     if (!connection){
1223                         // incoming connection
1224                         connection = avrcp_create_connection(event_addr, context);
1225                         if (!connection) {
1226                             log_error("Failed to alloc connection structure");
1227                             l2cap_disconnect(local_cid, 0); // reason isn't used
1228                             break;
1229                         }
1230                         connection->l2cap_signaling_cid = local_cid;
1231                         connection->avrcp_cid = avrcp_cid_counter++;
1232                     }
1233 
1234                     if (l2cap_event_channel_opened_get_status(packet)){
1235                         log_info("L2CAP connection to connection %s failed. status code 0x%02x",
1236                             bd_addr_to_str(event_addr), l2cap_event_channel_opened_get_status(packet));
1237                         if (connection->state == AVCTP_CONNECTION_W4_L2CAP_CONNECTED && connection->l2cap_signaling_cid == local_cid){
1238                             avrcp_emit_connection_established(avrcp_callback, connection->avrcp_cid, event_addr, l2cap_event_channel_opened_get_status(packet));
1239                         }
1240                         // free connection
1241                         btstack_linked_list_remove(&context->connections, (btstack_linked_item_t*) connection);
1242                         btstack_memory_avrcp_connection_free(connection);
1243                         break;
1244                     }
1245                     connection->l2cap_signaling_cid = local_cid;
1246                     log_info("L2CAP_EVENT_CHANNEL_OPENED avrcp_cid 0x%02x, l2cap_signaling_cid 0x%02x",connection->avrcp_cid, connection->l2cap_signaling_cid);
1247                     connection->state = AVCTP_CONNECTION_OPENED;
1248                     avrcp_emit_connection_established(avrcp_callback, connection->avrcp_cid, event_addr, ERROR_CODE_SUCCESS);
1249                     break;
1250 
1251                 case L2CAP_EVENT_CAN_SEND_NOW:
1252                     connection = get_avrcp_connection_for_l2cap_signaling_cid(channel, context);
1253                     if (!connection) break;
1254                     avrcp_handle_can_send_now(connection);
1255                     break;
1256 
1257                 case L2CAP_EVENT_CHANNEL_CLOSED:
1258                     // data: event (8), len(8), channel (16)
1259                     local_cid = l2cap_event_channel_closed_get_local_cid(packet);
1260                     connection = get_avrcp_connection_for_l2cap_signaling_cid(local_cid, context);
1261                     if (connection){
1262                         avrcp_emit_connection_closed(avrcp_callback, connection->avrcp_cid);
1263                         // free connection
1264                         btstack_linked_list_remove(&context->connections, (btstack_linked_item_t*) connection);
1265                         btstack_memory_avrcp_connection_free(connection);
1266                         break;
1267                     }
1268                     break;
1269                 default:
1270                     break;
1271             }
1272             break;
1273         default:
1274             break;
1275     }
1276 }
1277 
1278 static void avrcp_controller_packet_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
1279     packet_handler(packet_type, channel, packet, size, &avrcp_controller_context);
1280 }
1281 
1282 void avrcp_controller_init(void){
1283     avrcp_controller_context.role = AVRCP_CONTROLLER;
1284     avrcp_controller_context.connections = NULL;
1285     avrcp_controller_context.avrcp_callback = avrcp_callback;
1286     avrcp_controller_context.packet_handler = avrcp_controller_packet_handler;
1287     l2cap_register_service(&avrcp_controller_packet_handler, BLUETOOTH_PROTOCOL_AVCTP, 0xffff, LEVEL_0);
1288 }
1289 
1290 void avrcp_register_packet_handler(btstack_packet_handler_t callback){
1291     if (callback == NULL){
1292         log_error("avrcp_register_packet_handler called with NULL callback");
1293         return;
1294     }
1295     avrcp_callback = callback;
1296     avrcp_controller_context.avrcp_callback = avrcp_callback;
1297 }
1298 
1299 uint8_t avrcp_connect(bd_addr_t bd_addr, avrcp_context_t * context, uint16_t * avrcp_cid){
1300     avrcp_connection_t * connection = get_avrcp_connection_for_bd_addr(bd_addr, context);
1301     if (connection){
1302         return ERROR_CODE_COMMAND_DISALLOWED;
1303     }
1304 
1305     connection = avrcp_create_connection(bd_addr, context);
1306     if (!connection){
1307         log_error("avrcp: could not allocate connection struct.");
1308         return BTSTACK_MEMORY_ALLOC_FAILED;
1309     }
1310 
1311     if (!avrcp_cid) return L2CAP_LOCAL_CID_DOES_NOT_EXIST;
1312 
1313     *avrcp_cid = avrcp_cid_counter++;
1314     connection->avrcp_cid = *avrcp_cid;
1315 
1316     connection->state = AVCTP_SIGNALING_W4_SDP_QUERY_COMPLETE;
1317     sdp_query_context.avrcp_context = context;
1318     sdp_query_context.avrcp_l2cap_psm = 0;
1319     sdp_query_context.avrcp_version = 0;
1320     sdp_query_context.connection = connection;
1321 
1322     sdp_client_query_uuid16(&avrcp_handle_sdp_client_query_result, bd_addr, BLUETOOTH_PROTOCOL_AVCTP);
1323     return ERROR_CODE_SUCCESS;
1324 }
1325 
1326 uint8_t avrcp_controller_connect(bd_addr_t bd_addr, uint16_t * avrcp_cid){
1327     return avrcp_connect(bd_addr, &avrcp_controller_context, avrcp_cid);
1328 }
1329 
1330 uint8_t avrcp_unit_info(uint16_t avrcp_cid){
1331     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1332     if (!connection){
1333         log_error("avrcp_unit_info: could not find a connection.");
1334         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1335     }
1336     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
1337     connection->state = AVCTP_W2_SEND_COMMAND;
1338 
1339     connection->transaction_label++;
1340     connection->command_opcode = AVRCP_CMD_OPCODE_UNIT_INFO;
1341     connection->command_type = AVRCP_CTYPE_STATUS;
1342     connection->subunit_type = AVRCP_SUBUNIT_TYPE_UNIT; //vendor unique
1343     connection->subunit_id =   AVRCP_SUBUNIT_ID_IGNORE;
1344     memset(connection->cmd_operands, 0xFF, connection->cmd_operands_length);
1345     connection->cmd_operands_length = 5;
1346     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1347     return ERROR_CODE_SUCCESS;
1348 }
1349 
1350 static uint8_t avrcp_get_capabilities(uint16_t avrcp_cid, uint8_t capability_id){
1351     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1352     if (!connection){
1353         log_error("avrcp_get_capabilities: could not find a connection.");
1354         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1355     }
1356     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
1357     connection->state = AVCTP_W2_SEND_COMMAND;
1358 
1359     connection->transaction_label++;
1360     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
1361     connection->command_type = AVRCP_CTYPE_STATUS;
1362     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
1363     connection->subunit_id = AVRCP_SUBUNIT_ID;
1364     big_endian_store_24(connection->cmd_operands, 0, BT_SIG_COMPANY_ID);
1365     connection->cmd_operands[3] = AVRCP_PDU_ID_GET_CAPABILITIES; // PDU ID
1366     connection->cmd_operands[4] = 0;
1367     big_endian_store_16(connection->cmd_operands, 5, 1); // parameter length
1368     connection->cmd_operands[7] = capability_id;                  // capability ID
1369     connection->cmd_operands_length = 8;
1370     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1371     return ERROR_CODE_SUCCESS;
1372 }
1373 
1374 uint8_t avrcp_get_supported_company_ids(uint16_t avrcp_cid){
1375     return avrcp_get_capabilities(avrcp_cid, AVRCP_CAPABILITY_ID_COMPANY);
1376 }
1377 
1378 uint8_t avrcp_get_supported_events(uint16_t avrcp_cid){
1379     return avrcp_get_capabilities(avrcp_cid, AVRCP_CAPABILITY_ID_EVENT);
1380 }
1381 
1382 
1383 uint8_t avrcp_play(uint16_t avrcp_cid){
1384     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_PLAY, 0);
1385 }
1386 
1387 uint8_t avrcp_stop(uint16_t avrcp_cid){
1388     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_STOP, 0);
1389 }
1390 
1391 uint8_t avrcp_pause(uint16_t avrcp_cid){
1392     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_PAUSE, 0);
1393 }
1394 
1395 uint8_t avrcp_forward(uint16_t avrcp_cid){
1396     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_FORWARD, 0);
1397 }
1398 
1399 uint8_t avrcp_backward(uint16_t avrcp_cid){
1400     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_BACKWARD, 0);
1401 }
1402 
1403 uint8_t avrcp_start_rewind(uint16_t avrcp_cid){
1404     return request_continuous_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_REWIND, 0);
1405 }
1406 
1407 uint8_t avrcp_volume_up(uint16_t avrcp_cid){
1408     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_VOLUME_UP, 0);
1409 }
1410 
1411 uint8_t avrcp_volume_down(uint16_t avrcp_cid){
1412     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_VOLUME_DOWN, 0);
1413 }
1414 
1415 uint8_t avrcp_mute(uint16_t avrcp_cid){
1416     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_MUTE, 0);
1417 }
1418 
1419 uint8_t avrcp_skip(uint16_t avrcp_cid){
1420     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_SKIP, 0);
1421 }
1422 
1423 uint8_t avrcp_stop_rewind(uint16_t avrcp_cid){
1424     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1425     if (!connection){
1426         log_error("avrcp_stop_rewind: could not find a connection.");
1427         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1428     }
1429     if (connection->state != AVCTP_W4_STOP) return ERROR_CODE_COMMAND_DISALLOWED;
1430     return request_pass_through_release_control_cmd(connection);
1431 }
1432 
1433 uint8_t avrcp_start_fast_forward(uint16_t avrcp_cid){
1434     return request_continuous_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_FAST_FORWARD, 0);
1435 }
1436 
1437 uint8_t avrcp_fast_forward(uint16_t avrcp_cid){
1438     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_FAST_FORWARD, 0);
1439 }
1440 
1441 uint8_t avrcp_rewind(uint16_t avrcp_cid){
1442     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_REWIND, 0);
1443 }
1444 
1445 
1446 uint8_t avrcp_stop_fast_forward(uint16_t avrcp_cid){
1447     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1448     if (!connection){
1449         log_error("avrcp_stop_fast_forward: could not find a connection.");
1450         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1451     }
1452     if (connection->state != AVCTP_W4_STOP) return ERROR_CODE_COMMAND_DISALLOWED;
1453     return request_pass_through_release_control_cmd(connection);
1454 }
1455 
1456 uint8_t avrcp_get_play_status(uint16_t avrcp_cid){
1457     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1458     if (!connection){
1459         log_error("avrcp_get_play_status: could not find a connection.");
1460         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1461     }
1462     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
1463     connection->state = AVCTP_W2_SEND_COMMAND;
1464     connection->transaction_label++;
1465     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
1466     connection->command_type = AVRCP_CTYPE_STATUS;
1467     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
1468     connection->subunit_id = AVRCP_SUBUNIT_ID;
1469     big_endian_store_24(connection->cmd_operands, 0, BT_SIG_COMPANY_ID);
1470     connection->cmd_operands[3] = AVRCP_PDU_ID_GET_PLAY_STATUS;
1471     connection->cmd_operands[4] = 0;                     // reserved(upper 6) | packet_type -> 0
1472     big_endian_store_16(connection->cmd_operands, 5, 0); // parameter length
1473     connection->cmd_operands_length = 7;
1474     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1475     return ERROR_CODE_SUCCESS;
1476 }
1477 
1478 uint8_t avrcp_enable_notification(uint16_t avrcp_cid, avrcp_notification_event_id_t event_id){
1479     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1480     if (!connection){
1481         log_error("avrcp_get_play_status: could not find a connection.");
1482         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1483     }
1484     avrcp_register_notification(connection, event_id);
1485     return ERROR_CODE_SUCCESS;
1486 }
1487 
1488 uint8_t avrcp_disable_notification(uint16_t avrcp_cid, avrcp_notification_event_id_t event_id){
1489     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1490     if (!connection){
1491         log_error("avrcp_get_play_status: could not find a connection.");
1492         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1493     }
1494     connection->notifications_to_deregister |= (1 << event_id);
1495     return ERROR_CODE_SUCCESS;
1496 }
1497 
1498 uint8_t avrcp_get_now_playing_info(uint16_t avrcp_cid){
1499     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1500     if (!connection){
1501         log_error("avrcp_get_capabilities: could not find a connection.");
1502         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1503     }
1504     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
1505     connection->state = AVCTP_W2_SEND_COMMAND;
1506 
1507     connection->transaction_label++;
1508     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
1509     connection->command_type = AVRCP_CTYPE_STATUS;
1510     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
1511     connection->subunit_id = AVRCP_SUBUNIT_ID;
1512     int pos = 0;
1513     big_endian_store_24(connection->cmd_operands, pos, BT_SIG_COMPANY_ID);
1514     pos += 3;
1515     connection->cmd_operands[pos++] = AVRCP_PDU_ID_GET_ELEMENT_ATTRIBUTES; // PDU ID
1516     connection->cmd_operands[pos++] = 0;
1517 
1518     // Parameter Length
1519     big_endian_store_16(connection->cmd_operands, pos, 9);
1520     pos += 2;
1521 
1522     // write 8 bytes value
1523     memset(connection->cmd_operands + pos, 0, 8); // identifier: PLAYING
1524     pos += 8;
1525 
1526     connection->cmd_operands[pos++] = 0; // attribute count, if 0 get all attributes
1527     // every attribute is 4 bytes long
1528 
1529     connection->cmd_operands_length = pos;
1530     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1531     return ERROR_CODE_SUCCESS;
1532 }
1533 
1534 uint8_t avrcp_set_absolute_volume(uint16_t avrcp_cid, uint8_t volume){
1535      avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1536     if (!connection){
1537         log_error("avrcp_get_capabilities: could not find a connection.");
1538         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1539     }
1540     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
1541     connection->state = AVCTP_W2_SEND_COMMAND;
1542 
1543     connection->transaction_label++;
1544     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
1545     connection->command_type = AVRCP_CTYPE_CONTROL;
1546     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
1547     connection->subunit_id = AVRCP_SUBUNIT_ID;
1548     int pos = 0;
1549     big_endian_store_24(connection->cmd_operands, pos, BT_SIG_COMPANY_ID);
1550     pos += 3;
1551     connection->cmd_operands[pos++] = AVRCP_PDU_ID_SET_ABSOLUTE_VOLUME; // PDU ID
1552     connection->cmd_operands[pos++] = 0;
1553 
1554     // Parameter Length
1555     big_endian_store_16(connection->cmd_operands, pos, 1);
1556     pos += 2;
1557     connection->cmd_operands[pos++] = volume;
1558 
1559     connection->cmd_operands_length = pos;
1560     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1561     return ERROR_CODE_SUCCESS;
1562 }
1563 
1564 uint8_t avrcp_query_shuffle_and_repeat_modes(uint16_t avrcp_cid){
1565     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1566     if (!connection){
1567         log_error("avrcp_get_capabilities: could not find a connection.");
1568         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1569     }
1570     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
1571     connection->state = AVCTP_W2_SEND_COMMAND;
1572 
1573     connection->transaction_label++;
1574     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
1575     connection->command_type = AVRCP_CTYPE_STATUS;
1576     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
1577     connection->subunit_id = AVRCP_SUBUNIT_ID;
1578     big_endian_store_24(connection->cmd_operands, 0, BT_SIG_COMPANY_ID);
1579     connection->cmd_operands[3] = AVRCP_PDU_ID_GetCurrentPlayerApplicationSettingValue; // PDU ID
1580     connection->cmd_operands[4] = 0;
1581     big_endian_store_16(connection->cmd_operands, 5, 5); // parameter length
1582     connection->cmd_operands[7] = 4;                     // NumPlayerApplicationSettingAttributeID
1583     // PlayerApplicationSettingAttributeID1 AVRCP Spec, Appendix F, 133
1584     connection->cmd_operands[8]  = 0x01;    // equalizer  (1-OFF, 2-ON)
1585     connection->cmd_operands[9]  = 0x02;    // repeat     (1-off, 2-single track, 3-all tracks, 4-group repeat)
1586     connection->cmd_operands[10] = 0x03;    // shuffle    (1-off, 2-all tracks, 3-group shuffle)
1587     connection->cmd_operands[11] = 0x04;    // scan       (1-off, 2-all tracks, 3-group scan)
1588     connection->cmd_operands_length = 12;
1589     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1590     return ERROR_CODE_SUCCESS;
1591 }
1592 
1593 static uint8_t avrcp_set_current_player_application_setting_value(uint16_t avrcp_cid, uint8_t attr_id, uint8_t attr_value){
1594     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1595     if (!connection){
1596         log_error("avrcp_get_capabilities: could not find a connection.");
1597         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1598     }
1599     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
1600     connection->state = AVCTP_W2_SEND_COMMAND;
1601 
1602     connection->transaction_label++;
1603     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
1604     connection->command_type = AVRCP_CTYPE_CONTROL;
1605     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
1606     connection->subunit_id = AVRCP_SUBUNIT_ID;
1607     int pos = 0;
1608     big_endian_store_24(connection->cmd_operands, pos, BT_SIG_COMPANY_ID);
1609     pos += 3;
1610     connection->cmd_operands[pos++] = AVRCP_PDU_ID_SetPlayerApplicationSettingValue; // PDU ID
1611     connection->cmd_operands[pos++] = 0;
1612     // Parameter Length
1613     big_endian_store_16(connection->cmd_operands, pos, 3);
1614     pos += 2;
1615     connection->cmd_operands[pos++] = 2;
1616     connection->cmd_operands_length = pos;
1617     connection->cmd_operands[pos++]  = attr_id;
1618     connection->cmd_operands[pos++]  = attr_value;
1619     connection->cmd_operands_length = pos;
1620     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1621     return ERROR_CODE_SUCCESS;
1622 }
1623 
1624 uint8_t avrcp_set_shuffle_mode(uint16_t avrcp_cid, avrcp_shuffle_mode_t mode){
1625     if (mode < AVRCP_SHUFFLE_MODE_OFF || mode > AVRCP_SHUFFLE_MODE_GROUP) return ERROR_CODE_UNSUPPORTED_FEATURE_OR_PARAMETER_VALUE;
1626     return avrcp_set_current_player_application_setting_value(avrcp_cid, 0x03, mode);
1627 }
1628 
1629 uint8_t avrcp_set_repeat_mode(uint16_t avrcp_cid, avrcp_repeat_mode_t mode){
1630     if (mode < AVRCP_REPEAT_MODE_OFF || mode > AVRCP_REPEAT_MODE_GROUP) return ERROR_CODE_UNSUPPORTED_FEATURE_OR_PARAMETER_VALUE;
1631     return avrcp_set_current_player_application_setting_value(avrcp_cid, 0x02, mode);
1632 }
1633 
1634 uint8_t avrcp_disconnect(uint16_t avrcp_cid){
1635     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1636     if (!connection){
1637         log_error("avrcp_get_capabilities: could not find a connection.");
1638         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1639     }
1640     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
1641     l2cap_disconnect(connection->l2cap_signaling_cid, 0);
1642     return ERROR_CODE_SUCCESS;
1643 }