xref: /btstack/src/classic/avrcp_controller.c (revision c823631b5a0ff4a81ba4e8da529d5334f8dd60c7)
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_controller.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 #include "classic/avrcp_controller.h"
48 
49 static avrcp_context_t avrcp_controller_context;
50 
51 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){
52     avrcp_create_sdp_record(1, service, service_record_handle, browsing, supported_features, service_name, service_provider_name);
53 }
54 
55 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){
56     if (!callback) return;
57     uint8_t event[8];
58     int pos = 0;
59     event[pos++] = HCI_EVENT_AVRCP_META;
60     event[pos++] = sizeof(event) - 2;
61     event[pos++] = AVRCP_SUBEVENT_SHUFFLE_AND_REPEAT_MODE;
62     little_endian_store_16(event, pos, avrcp_cid);
63     pos += 2;
64     event[pos++] = ctype;
65     event[pos++] = repeat_mode;
66     event[pos++] = shuffle_mode;
67     (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
68 }
69 
70 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){
71     if (!callback) return;
72     uint8_t event[7];
73     int pos = 0;
74     event[pos++] = HCI_EVENT_AVRCP_META;
75     event[pos++] = sizeof(event) - 2;
76     event[pos++] = subevent;
77     little_endian_store_16(event, pos, avrcp_cid);
78     pos += 2;
79     event[pos++] = ctype;
80     event[pos++] = operation_id;
81     (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
82 }
83 
84 static void avrcp_press_and_hold_timeout_handler(btstack_timer_source_t * timer){
85     UNUSED(timer);
86     avrcp_connection_t * connection = btstack_run_loop_get_timer_context(timer);
87     btstack_run_loop_set_timer(&connection->press_and_hold_cmd_timer, 2000); // 2 seconds timeout
88     btstack_run_loop_add_timer(&connection->press_and_hold_cmd_timer);
89     connection->state = AVCTP_W2_SEND_PRESS_COMMAND;
90     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
91 }
92 
93 static void avrcp_press_and_hold_timer_start(avrcp_connection_t * connection){
94     btstack_run_loop_remove_timer(&connection->press_and_hold_cmd_timer);
95     btstack_run_loop_set_timer_handler(&connection->press_and_hold_cmd_timer, avrcp_press_and_hold_timeout_handler);
96     btstack_run_loop_set_timer_context(&connection->press_and_hold_cmd_timer, connection);
97     btstack_run_loop_set_timer(&connection->press_and_hold_cmd_timer, 2000); // 2 seconds timeout
98     btstack_run_loop_add_timer(&connection->press_and_hold_cmd_timer);
99 }
100 
101 static void avrcp_press_and_hold_timer_stop(avrcp_connection_t * connection){
102     connection->continuous_fast_forward_cmd = 0;
103     btstack_run_loop_remove_timer(&connection->press_and_hold_cmd_timer);
104 }
105 
106 static uint8_t request_pass_through_release_control_cmd(avrcp_connection_t * connection){
107     connection->state = AVCTP_W2_SEND_RELEASE_COMMAND;
108     if (connection->continuous_fast_forward_cmd){
109         avrcp_press_and_hold_timer_stop(connection);
110     }
111     connection->cmd_operands[0] = 0x80 | connection->cmd_operands[0];
112     connection->transaction_label++;
113     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
114     return ERROR_CODE_SUCCESS;
115 }
116 
117 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){
118     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, context);
119     if (!connection){
120         log_error("avrcp: could not find a connection.");
121         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
122     }
123     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
124     connection->state = AVCTP_W2_SEND_PRESS_COMMAND;
125     connection->command_opcode =  AVRCP_CMD_OPCODE_PASS_THROUGH;
126     connection->command_type = AVRCP_CTYPE_CONTROL;
127     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
128     connection->subunit_id =   AVRCP_SUBUNIT_ID;
129     connection->cmd_operands_length = 0;
130 
131     connection->continuous_fast_forward_cmd = continuous_fast_forward_cmd;
132     connection->cmd_operands_length = 2;
133     connection->cmd_operands[0] = opid;
134     if (playback_speed > 0){
135         connection->cmd_operands[2] = playback_speed;
136         connection->cmd_operands_length++;
137     }
138     connection->cmd_operands[1] = connection->cmd_operands_length - 2;
139 
140     if (connection->continuous_fast_forward_cmd){
141         avrcp_press_and_hold_timer_start(connection);
142     }
143 
144     connection->transaction_label++;
145     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
146     return ERROR_CODE_SUCCESS;
147 }
148 
149 static uint8_t request_single_pass_through_press_control_cmd(uint16_t avrcp_cid, avrcp_operation_id_t opid, uint16_t playback_speed){
150     return request_pass_through_press_control_cmd(avrcp_cid, opid, playback_speed, 0, &avrcp_controller_context);
151 }
152 
153 static uint8_t request_continuous_pass_through_press_control_cmd(uint16_t avrcp_cid, avrcp_operation_id_t opid, uint16_t playback_speed){
154     return request_pass_through_press_control_cmd(avrcp_cid, opid, playback_speed, 1, &avrcp_controller_context);
155 }
156 
157 static int avrcp_send_cmd(uint16_t cid, avrcp_connection_t * connection){
158     uint8_t command[30];
159     int pos = 0;
160     // transport header
161     // Transaction label | Packet_type | C/R | IPID (1 == invalid profile identifier)
162     command[pos++] = (connection->transaction_label << 4) | (AVRCP_SINGLE_PACKET << 2) | (AVRCP_COMMAND_FRAME << 1) | 0;
163     // Profile IDentifier (PID)
164     command[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL >> 8;
165     command[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL & 0x00FF;
166 
167     // command_type
168     command[pos++] = connection->command_type;
169     // subunit_type | subunit ID
170     command[pos++] = (connection->subunit_type << 3) | connection->subunit_id;
171     // opcode
172     command[pos++] = (uint8_t)connection->command_opcode;
173     // operands
174     memcpy(command+pos, connection->cmd_operands, connection->cmd_operands_length);
175     pos += connection->cmd_operands_length;
176 
177     return l2cap_send(cid, command, pos);
178 }
179 
180 static int avrcp_register_notification(avrcp_connection_t * connection, avrcp_notification_event_id_t event_id){
181     if (connection->notifications_to_deregister & (1 << event_id)) return 0;
182     if (connection->notifications_enabled & (1 << event_id)) return 0;
183     if (connection->notifications_to_register & (1 << event_id)) return 0;
184     connection->notifications_to_register |= (1 << event_id);
185     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
186     return 1;
187 }
188 
189 static void avrcp_prepare_notification(avrcp_connection_t * connection, avrcp_notification_event_id_t event_id){
190     connection->transaction_label++;
191     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
192     connection->command_type = AVRCP_CTYPE_NOTIFY;
193     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
194     connection->subunit_id = AVRCP_SUBUNIT_ID;
195     int pos = 0;
196     big_endian_store_24(connection->cmd_operands, pos, BT_SIG_COMPANY_ID);
197     pos += 3;
198     connection->cmd_operands[pos++] = AVRCP_PDU_ID_REGISTER_NOTIFICATION;
199     connection->cmd_operands[pos++] = 0;                     // reserved(upper 6) | packet_type -> 0
200     big_endian_store_16(connection->cmd_operands, pos, 5);     // parameter length
201     pos += 2;
202     connection->cmd_operands[pos++] = event_id;
203     big_endian_store_32(connection->cmd_operands, pos, 0);
204     pos += 4;
205     connection->cmd_operands_length = pos;
206     // AVRCP_SPEC_V14.pdf 166
207     // answer page 61
208 }
209 
210 static uint8_t avrcp_cmd_opcode(uint8_t *packet, uint16_t size){
211     uint8_t cmd_opcode_index = 5;
212     if (cmd_opcode_index > size) return AVRCP_CMD_OPCODE_UNDEFINED;
213     return packet[cmd_opcode_index];
214 }
215 
216 
217 static void avrcp_handle_l2cap_data_packet_for_signaling_connection(avrcp_connection_t * connection, uint8_t *packet, uint16_t size){
218     uint8_t operands[20];
219     uint8_t opcode;
220     int     pos = 3;
221     // uint8_t transport_header = packet[0];
222     // uint8_t transaction_label = transport_header >> 4;
223     // uint8_t packet_type = (transport_header & 0x0F) >> 2;
224     // uint8_t frame_type = (transport_header & 0x03) >> 1;
225     // uint8_t ipid = transport_header & 0x01;
226     // uint8_t byte_value = packet[2];
227     // uint16_t pid = (byte_value << 8) | packet[2];
228 
229     avrcp_command_type_t ctype = (avrcp_command_type_t) packet[pos++];
230     uint8_t byte_value = packet[pos++];
231     avrcp_subunit_type_t subunit_type = (avrcp_subunit_type_t) (byte_value >> 3);
232     avrcp_subunit_type_t subunit_id = (avrcp_subunit_type_t)   (byte_value & 0x07);
233     opcode = packet[pos++];
234 
235     // printf("    Transport header 0x%02x (transaction_label %d, packet_type %d, frame_type %d, ipid %d), pid 0x%4x\n",
236     //     transport_header, transaction_label, packet_type, frame_type, ipid, pid);
237     // // printf_hexdump(packet+pos, size-pos);
238 
239     uint8_t pdu_id;
240     uint16_t param_length;
241     switch (avrcp_cmd_opcode(packet,size)){
242         case AVRCP_CMD_OPCODE_UNIT_INFO:{
243             if (connection->state != AVCTP_W2_RECEIVE_RESPONSE) return;
244             connection->state = AVCTP_CONNECTION_OPENED;
245 
246             // operands:
247             memcpy(operands, packet+pos, 5);
248             uint8_t unit_type = operands[1] >> 3;
249             uint8_t unit = operands[1] & 0x07;
250             uint32_t company_id = operands[2] << 16 | operands[3] << 8 | operands[4];
251             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",
252                 ctype, subunit_type, subunit_id, opcode, unit_type, unit, company_id );
253             break;
254         }
255         case AVRCP_CMD_OPCODE_VENDOR_DEPENDENT:
256             if (size - pos < 7) {
257                 log_error("avrcp: wrong packet size");
258                 return;
259             };
260             // operands:
261             memcpy(operands, packet+pos, 7);
262             pos += 7;
263             // uint32_t company_id = operands[0] << 16 | operands[1] << 8 | operands[2];
264             pdu_id = operands[3];
265 
266             if (connection->state != AVCTP_W2_RECEIVE_RESPONSE && pdu_id != AVRCP_PDU_ID_REGISTER_NOTIFICATION){
267                 log_info("AVRCP_CMD_OPCODE_VENDOR_DEPENDENT state %d", connection->state);
268                 return;
269             }
270             connection->state = AVCTP_CONNECTION_OPENED;
271 
272 
273             // uint8_t unit_type = operands[4] >> 3;
274             // uint8_t unit = operands[4] & 0x07;
275             param_length = big_endian_read_16(operands, 5);
276 
277             // 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",
278             //     ctype, subunit_type, subunit_id, opcode, unit_type, unit, company_id );
279 
280             // if (ctype == AVRCP_CTYPE_RESPONSE_INTERIM) return;
281             log_info("        VENDOR DEPENDENT response: pdu id 0x%02x, param_length %d, status %s", pdu_id, param_length, avrcp_ctype2str(ctype));
282             switch (pdu_id){
283                 case AVRCP_PDU_ID_GetCurrentPlayerApplicationSettingValue:{
284                     uint8_t num_attributes = packet[pos++];
285                     int i;
286                     avrcp_repeat_mode_t  repeat_mode =  AVRCP_REPEAT_MODE_INVALID;
287                     avrcp_shuffle_mode_t shuffle_mode = AVRCP_SHUFFLE_MODE_INVALID;
288                     for (i = 0; i < num_attributes; i++){
289                         uint8_t attribute_id    = packet[pos++];
290                         uint8_t value = packet[pos++];
291                         switch (attribute_id){
292                             case 0x02:
293                                 repeat_mode = (avrcp_repeat_mode_t) value;
294                                 break;
295                             case 0x03:
296                                 shuffle_mode = (avrcp_shuffle_mode_t) value;
297                                 break;
298                             default:
299                                 break;
300                         }
301                     }
302                     avrcp_emit_repeat_and_shuffle_mode(avrcp_controller_context.avrcp_callback, connection->avrcp_cid, ctype, repeat_mode, shuffle_mode);
303                     break;
304                 }
305                 case AVRCP_PDU_ID_SetPlayerApplicationSettingValue:{
306                     uint8_t event[6];
307                     int offset = 0;
308                     event[offset++] = HCI_EVENT_AVRCP_META;
309                     event[offset++] = sizeof(event) - 2;
310                     event[offset++] = AVRCP_SUBEVENT_PLAYER_APPLICATION_VALUE_RESPONSE;
311                     little_endian_store_16(event, offset, connection->avrcp_cid);
312                     offset += 2;
313                     event[offset++] = ctype;
314                     (*avrcp_controller_context.avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
315                     break;
316                 }
317                 case AVRCP_PDU_ID_SET_ABSOLUTE_VOLUME:{
318                     uint8_t event[7];
319                     int offset = 0;
320                     event[offset++] = HCI_EVENT_AVRCP_META;
321                     event[offset++] = sizeof(event) - 2;
322                     event[offset++] = AVRCP_SUBEVENT_SET_ABSOLUTE_VOLUME_RESPONSE;
323                     little_endian_store_16(event, offset, connection->avrcp_cid);
324                     offset += 2;
325                     event[offset++] = ctype;
326                     event[offset++] = packet[pos++];
327                     (*avrcp_controller_context.avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
328                     break;
329                 }
330                 case AVRCP_PDU_ID_GET_CAPABILITIES:{
331                     avrcp_capability_id_t capability_id = (avrcp_capability_id_t) packet[pos++];
332                     uint8_t capability_count = packet[pos++];
333                     int i;
334                     switch (capability_id){
335                         case AVRCP_CAPABILITY_ID_COMPANY:
336                             // log_info("Supported companies %d: ", capability_count);
337                             for (i = 0; i < capability_count; i++){
338                                 uint32_t company_id = big_endian_read_24(packet, pos);
339                                 pos += 3;
340                                 log_info("  0x%06x, ", company_id);
341                             }
342                             break;
343                         case AVRCP_CAPABILITY_ID_EVENT:
344                             // log_info("Supported events %d: ", capability_count);
345                             for (i = 0; i < capability_count; i++){
346                                 uint8_t event_id = packet[pos++];
347                                 log_info("  0x%02x %s", event_id, avrcp_event2str(event_id));
348                             }
349                             break;
350                     }
351                     break;
352                 }
353                 case AVRCP_PDU_ID_GET_PLAY_STATUS:{
354                     uint32_t song_length = big_endian_read_32(packet, pos);
355                     pos += 4;
356                     uint32_t song_position = big_endian_read_32(packet, pos);
357                     pos += 4;
358                     uint8_t play_status = packet[pos];
359                     // log_info("        GET_PLAY_STATUS length 0x%04X, position 0x%04X, status %s", song_length, song_position, avrcp_play_status2str(play_status));
360 
361                     uint8_t event[15];
362                     int offset = 0;
363                     event[offset++] = HCI_EVENT_AVRCP_META;
364                     event[offset++] = sizeof(event) - 2;
365                     event[offset++] = AVRCP_SUBEVENT_PLAY_STATUS;
366                     little_endian_store_16(event, offset, connection->avrcp_cid);
367                     offset += 2;
368                     event[offset++] = ctype;
369                     little_endian_store_32(event, offset, song_length);
370                     offset += 4;
371                     little_endian_store_32(event, offset, song_position);
372                     offset += 4;
373                     event[offset++] = play_status;
374                     (*avrcp_controller_context.avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
375                     break;
376                 }
377                 case AVRCP_PDU_ID_REGISTER_NOTIFICATION:{
378                     avrcp_notification_event_id_t  event_id = (avrcp_notification_event_id_t) packet[pos++];
379                     uint16_t event_mask = (1 << event_id);
380                     uint16_t reset_event_mask = ~event_mask;
381                     switch (ctype){
382                         case AVRCP_CTYPE_RESPONSE_INTERIM:
383                             // register as enabled
384                             connection->notifications_enabled |= event_mask;
385                             // printf("INTERIM notifications_enabled 0x%2x, notifications_to_register 0x%2x\n", connection->notifications_enabled,  connection->notifications_to_register);
386                             break;
387                         case AVRCP_CTYPE_RESPONSE_CHANGED_STABLE:
388                             // received change, event is considered deregistered
389                             // we are re-enabling it automatically, if it is not
390                             // explicitly disabled
391                             connection->notifications_enabled &= reset_event_mask;
392                             if (! (connection->notifications_to_deregister & event_mask)){
393                                 avrcp_register_notification(connection, event_id);
394                                 // printf("CHANGED_STABLE notifications_enabled 0x%2x, notifications_to_register 0x%2x\n", connection->notifications_enabled,  connection->notifications_to_register);
395                             } else {
396                                 connection->notifications_to_deregister &= reset_event_mask;
397                             }
398                             break;
399                         default:
400                             connection->notifications_to_register &= reset_event_mask;
401                             connection->notifications_enabled &= reset_event_mask;
402                             connection->notifications_to_deregister &= reset_event_mask;
403                             break;
404                     }
405 
406                     switch (event_id){
407                         case AVRCP_NOTIFICATION_EVENT_PLAYBACK_STATUS_CHANGED:{
408                             uint8_t event[7];
409                             int offset = 0;
410                             event[offset++] = HCI_EVENT_AVRCP_META;
411                             event[offset++] = sizeof(event) - 2;
412                             event[offset++] = AVRCP_SUBEVENT_NOTIFICATION_PLAYBACK_STATUS_CHANGED;
413                             little_endian_store_16(event, offset, connection->avrcp_cid);
414                             offset += 2;
415                             event[offset++] = ctype;
416                             event[offset++] = packet[pos];
417                             (*avrcp_controller_context.avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
418                             break;
419                         }
420                         case AVRCP_NOTIFICATION_EVENT_TRACK_CHANGED:{
421                             uint8_t event[6];
422                             int offset = 0;
423                             event[offset++] = HCI_EVENT_AVRCP_META;
424                             event[offset++] = sizeof(event) - 2;
425                             event[offset++] = AVRCP_SUBEVENT_NOTIFICATION_TRACK_CHANGED;
426                             little_endian_store_16(event, offset, connection->avrcp_cid);
427                             offset += 2;
428                             event[offset++] = ctype;
429                             (*avrcp_controller_context.avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
430                             break;
431                         }
432                         case AVRCP_NOTIFICATION_EVENT_NOW_PLAYING_CONTENT_CHANGED:{
433                             uint8_t event[6];
434                             int offset = 0;
435                             event[offset++] = HCI_EVENT_AVRCP_META;
436                             event[offset++] = sizeof(event) - 2;
437                             event[offset++] = AVRCP_SUBEVENT_NOTIFICATION_NOW_PLAYING_CONTENT_CHANGED;
438                             little_endian_store_16(event, offset, connection->avrcp_cid);
439                             offset += 2;
440                             event[offset++] = ctype;
441                             (*avrcp_controller_context.avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
442                             break;
443                         }
444                         case AVRCP_NOTIFICATION_EVENT_AVAILABLE_PLAYERS_CHANGED:{
445                             uint8_t event[6];
446                             int offset = 0;
447                             event[offset++] = HCI_EVENT_AVRCP_META;
448                             event[offset++] = sizeof(event) - 2;
449                             event[offset++] = AVRCP_SUBEVENT_NOTIFICATION_AVAILABLE_PLAYERS_CHANGED;
450                             little_endian_store_16(event, offset, connection->avrcp_cid);
451                             offset += 2;
452                             event[offset++] = ctype;
453                             (*avrcp_controller_context.avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
454                             break;
455                         }
456                         case AVRCP_NOTIFICATION_EVENT_VOLUME_CHANGED:{
457                             uint8_t event[7];
458                             int offset = 0;
459                             event[offset++] = HCI_EVENT_AVRCP_META;
460                             event[offset++] = sizeof(event) - 2;
461                             event[offset++] = AVRCP_SUBEVENT_NOTIFICATION_VOLUME_CHANGED;
462                             little_endian_store_16(event, offset, connection->avrcp_cid);
463                             offset += 2;
464                             event[offset++] = ctype;
465                             event[offset++] = packet[pos++] & 0x7F;
466                             (*avrcp_controller_context.avrcp_callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
467                             break;
468                         }
469                         // case AVRCP_NOTIFICATION_EVENT_PLAYER_APPLICATION_SETTING_CHANGED:{
470                         //     uint8_t num_PlayerApplicationSettingAttributes = packet[pos++];
471                         //     int i;
472                         //     for (i = 0; i < num_PlayerApplicationSettingAttributes; i++){
473                         //         uint8_t PlayerApplicationSetting_AttributeID = packet[pos++];
474                         //         uint8_t PlayerApplicationSettingValueID = packet[pos++];
475                         //     }
476                         //     break;
477                         // }
478                         // case AVRCP_NOTIFICATION_EVENT_ADDRESSED_PLAYER_CHANGED:
479                         //     uint16_t player_id = big_endian_read_16(packet, pos);
480                         //     pos += 2;
481                         //     uint16_t uid_counter = big_endian_read_16(packet, pos);
482                         //     pos += 2;
483                         //     break;
484                         // case AVRCP_NOTIFICATION_EVENT_UIDS_CHANGED:
485                         //     uint16_t uid_counter = big_endian_read_16(packet, pos);
486                         //     pos += 2;
487                         //     break;
488                         default:
489                             log_info("avrcp: not implemented");
490                             break;
491                     }
492                     if (connection->notifications_to_register != 0){
493                         avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
494                     }
495                     break;
496                 }
497 
498                 case AVRCP_PDU_ID_GET_ELEMENT_ATTRIBUTES:{
499                     uint8_t num_attributes = packet[pos++];
500                     int i;
501                     struct item {
502                         uint16_t len;
503                         uint8_t  * value;
504                     } items[AVRCP_MEDIA_ATTR_COUNT];
505                     memset(items, 0, sizeof(items));
506 
507                     uint16_t string_attributes_len = 0;
508                     uint8_t  num_string_attributes = 0;
509                     uint16_t total_event_payload_for_string_attributes = HCI_EVENT_PAYLOAD_SIZE-2;
510                     uint16_t max_string_attribute_value_len = 0;
511                     if (ctype == AVRCP_CTYPE_RESPONSE_IMPLEMENTED_STABLE || ctype == AVRCP_CTYPE_RESPONSE_CHANGED_STABLE){
512                         for (i = 0; i < num_attributes; i++){
513                             avrcp_media_attribute_id_t attr_id = (avrcp_media_attribute_id_t) big_endian_read_32(packet, pos);
514                             pos += 4;
515                             // uint16_t character_set = big_endian_read_16(packet, pos);
516                             pos += 2;
517                             uint16_t attr_value_length = big_endian_read_16(packet, pos);
518                             pos += 2;
519 
520                             // debug - to remove later
521                             uint8_t  value[100];
522                             uint16_t value_len = sizeof(value) <= attr_value_length? sizeof(value) - 1 : attr_value_length;
523                             memcpy(value, packet+pos, value_len);
524                             value[value_len] = 0;
525                             // printf("Now Playing Info %s: %s \n", attribute2str(attr_id), value);
526                             // end debug
527 
528                             if ((attr_id >= 1) || (attr_id <= AVRCP_MEDIA_ATTR_COUNT)) {
529                                 items[attr_id-1].len = attr_value_length;
530                                 items[attr_id-1].value = &packet[pos];
531                                 switch (attr_id){
532                                     case AVRCP_MEDIA_ATTR_TITLE:
533                                     case AVRCP_MEDIA_ATTR_ARTIST:
534                                     case AVRCP_MEDIA_ATTR_ALBUM:
535                                     case AVRCP_MEDIA_ATTR_GENRE:
536                                         num_string_attributes++;
537                                         string_attributes_len += attr_value_length;
538                                         if (max_string_attribute_value_len < attr_value_length){
539                                             max_string_attribute_value_len = attr_value_length;
540                                         }
541                                         break;
542                                     default:
543                                         break;
544                                 }
545                             }
546                             pos += attr_value_length;
547                         }
548                     }
549 
550                     // subtract space for fixed fields
551                     total_event_payload_for_string_attributes -= 14 + 4;    // 4 for '\0'
552 
553                     // @TODO optimize space by repeatedly decreasing max_string_attribute_value_len until it fits into buffer instead of crude divion
554                     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;
555                     // 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);
556 
557                     const uint8_t attribute_order[] = {
558                         AVRCP_MEDIA_ATTR_TRACK,
559                         AVRCP_MEDIA_ATTR_TOTAL_TRACKS,
560                         AVRCP_MEDIA_ATTR_SONG_LENGTH,
561                         AVRCP_MEDIA_ATTR_TITLE,
562                         AVRCP_MEDIA_ATTR_ARTIST,
563                         AVRCP_MEDIA_ATTR_ALBUM,
564                         AVRCP_MEDIA_ATTR_GENRE
565                     };
566 
567                     uint8_t event[HCI_EVENT_BUFFER_SIZE];
568                     event[0] = HCI_EVENT_AVRCP_META;
569                     pos = 2;
570                     event[pos++] = AVRCP_SUBEVENT_NOW_PLAYING_INFO;
571                     little_endian_store_16(event, pos, connection->avrcp_cid);
572                     pos += 2;
573                     event[pos++] = ctype;
574                     for (i = 0; i < sizeof(attribute_order); i++){
575                         avrcp_media_attribute_id_t attr_id = (avrcp_media_attribute_id_t) attribute_order[i];
576                         uint16_t value_len = 0;
577                         switch (attr_id){
578                             case AVRCP_MEDIA_ATTR_TITLE:
579                             case AVRCP_MEDIA_ATTR_ARTIST:
580                             case AVRCP_MEDIA_ATTR_ALBUM:
581                             case AVRCP_MEDIA_ATTR_GENRE:
582                                 if (items[attr_id-1].value){
583                                     value_len = items[attr_id-1].len <= max_value_len ? items[attr_id-1].len : max_value_len;
584                                 }
585                                 event[pos++] = value_len + 1;
586                                 if (value_len){
587                                     memcpy(event+pos, items[attr_id-1].value, value_len);
588                                     pos += value_len;
589                                 }
590                                 event[pos++] = 0;
591                                 break;
592                             case AVRCP_MEDIA_ATTR_SONG_LENGTH:
593                                 if (items[attr_id-1].value){
594                                     little_endian_store_32(event, pos, btstack_atoi((char *)items[attr_id-1].value));
595                                 } else {
596                                     little_endian_store_32(event, pos, 0);
597                                 }
598                                 pos += 4;
599                                 break;
600                             case AVRCP_MEDIA_ATTR_TRACK:
601                             case AVRCP_MEDIA_ATTR_TOTAL_TRACKS:
602                                 if (items[attr_id-1].value){
603                                     event[pos++] = btstack_atoi((char *)items[attr_id-1].value);
604                                 } else {
605                                     event[pos++] = 0;
606                                 }
607                                 break;
608                         }
609                     }
610                     event[1] = pos - 2;
611                     // printf_hexdump(event, pos);
612                     (*avrcp_controller_context.avrcp_callback)(HCI_EVENT_PACKET, 0, event, pos);
613                     break;
614                 }
615                 default:
616                     break;
617             }
618             break;
619         case AVRCP_CMD_OPCODE_PASS_THROUGH:{
620             // 0x80 | connection->cmd_operands[0]
621             uint8_t operation_id = packet[pos++];
622             switch (connection->state){
623                 case AVCTP_W2_RECEIVE_PRESS_RESPONSE:
624                     if (connection->continuous_fast_forward_cmd){
625                         connection->state = AVCTP_W4_STOP;
626                     } else {
627                         connection->state = AVCTP_W2_SEND_RELEASE_COMMAND;
628                     }
629                     break;
630                 case AVCTP_W2_RECEIVE_RESPONSE:
631                     connection->state = AVCTP_CONNECTION_OPENED;
632                     break;
633                 default:
634                     // check for notifications? move state transition down
635                     // log_info("AVRCP_CMD_OPCODE_PASS_THROUGH state %d\n", connection->state);
636                     break;
637             }
638             if (connection->state == AVCTP_W4_STOP){
639                 avrcp_emit_operation_status(avrcp_controller_context.avrcp_callback, AVRCP_SUBEVENT_OPERATION_START, connection->avrcp_cid, ctype, operation_id);
640             }
641             if (connection->state == AVCTP_CONNECTION_OPENED) {
642                 // RELEASE response
643                 operation_id = operation_id & 0x7F;
644                 avrcp_emit_operation_status(avrcp_controller_context.avrcp_callback, AVRCP_SUBEVENT_OPERATION_COMPLETE, connection->avrcp_cid, ctype, operation_id);
645             }
646             if (connection->state == AVCTP_W2_SEND_RELEASE_COMMAND){
647                 // PRESS response
648                 request_pass_through_release_control_cmd(connection);
649             }
650             break;
651         }
652         default:
653             break;
654     }
655 }
656 
657 static void avrcp_controller_handle_can_send_now(avrcp_connection_t * connection){
658     int i;
659     switch (connection->state){
660         case AVCTP_W2_SEND_PRESS_COMMAND:
661             connection->state = AVCTP_W2_RECEIVE_PRESS_RESPONSE;
662             avrcp_send_cmd(connection->l2cap_signaling_cid, connection);
663             break;
664         case AVCTP_W2_SEND_COMMAND:
665         case AVCTP_W2_SEND_RELEASE_COMMAND:
666             connection->state = AVCTP_W2_RECEIVE_RESPONSE;
667             avrcp_send_cmd(connection->l2cap_signaling_cid, connection);
668             break;
669         case AVCTP_CONNECTION_OPENED:
670             if (connection->notifications_to_register != 0){
671                 for (i = 1; i <= AVRCP_NOTIFICATION_EVENT_VOLUME_CHANGED; i++){
672                     if (connection->notifications_to_register & (1<<i)){
673                         connection->notifications_to_register &= ~ (1 << i);
674                         avrcp_prepare_notification(connection, (avrcp_notification_event_id_t) i);
675                         connection->state = AVCTP_W2_RECEIVE_RESPONSE;
676                         avrcp_send_cmd(connection->l2cap_signaling_cid, connection);
677                         return;
678                     }
679                 }
680             }
681             return;
682         default:
683             return;
684     }
685 }
686 
687 static void avrcp_controller_packet_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
688     avrcp_connection_t * connection;
689 
690     switch (packet_type) {
691         case L2CAP_DATA_PACKET:
692             connection = get_avrcp_connection_for_l2cap_signaling_cid(channel, &avrcp_controller_context);
693             if (!connection) break;
694             avrcp_handle_l2cap_data_packet_for_signaling_connection(connection, packet, size);
695             break;
696         case HCI_EVENT_PACKET:
697             switch (hci_event_packet_get_type(packet)){
698                 case L2CAP_EVENT_CAN_SEND_NOW:
699                     connection = get_avrcp_connection_for_l2cap_signaling_cid(channel, &avrcp_controller_context);
700                     if (!connection) break;
701                     avrcp_controller_handle_can_send_now(connection);
702                     break;
703             default:
704                 avrcp_packet_handler(packet_type, channel, packet, size, &avrcp_controller_context);
705                 break;
706         }
707         default:
708             break;
709     }
710 }
711 
712 void avrcp_controller_init(void){
713     avrcp_controller_context.role = AVRCP_CONTROLLER;
714     avrcp_controller_context.connections = NULL;
715     avrcp_controller_context.packet_handler = avrcp_controller_packet_handler;
716     l2cap_register_service(&avrcp_controller_packet_handler, BLUETOOTH_PROTOCOL_AVCTP, 0xffff, LEVEL_0);
717 }
718 
719 void avrcp_controller_register_packet_handler(btstack_packet_handler_t callback){
720     if (callback == NULL){
721         log_error("avrcp_register_packet_handler called with NULL callback");
722         return;
723     }
724     avrcp_controller_context.avrcp_callback = callback;
725 }
726 
727 uint8_t avrcp_controller_connect(bd_addr_t bd_addr, uint16_t * avrcp_cid){
728     return avrcp_connect(bd_addr, &avrcp_controller_context, avrcp_cid);
729 }
730 
731 uint8_t avrcp_controller_unit_info(uint16_t avrcp_cid){
732     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
733     if (!connection){
734         log_error("avrcp_unit_info: could not find a connection.");
735         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
736     }
737     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
738     connection->state = AVCTP_W2_SEND_COMMAND;
739 
740     connection->transaction_label++;
741     connection->command_opcode = AVRCP_CMD_OPCODE_UNIT_INFO;
742     connection->command_type = AVRCP_CTYPE_STATUS;
743     connection->subunit_type = AVRCP_SUBUNIT_TYPE_UNIT; //vendor unique
744     connection->subunit_id =   AVRCP_SUBUNIT_ID_IGNORE;
745     memset(connection->cmd_operands, 0xFF, connection->cmd_operands_length);
746     connection->cmd_operands_length = 5;
747     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
748     return ERROR_CODE_SUCCESS;
749 }
750 
751 static uint8_t avrcp_controller_get_capabilities(uint16_t avrcp_cid, uint8_t capability_id){
752     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
753     if (!connection){
754         log_error("avrcp_get_capabilities: could not find a connection.");
755         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
756     }
757     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
758     connection->state = AVCTP_W2_SEND_COMMAND;
759 
760     connection->transaction_label++;
761     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
762     connection->command_type = AVRCP_CTYPE_STATUS;
763     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
764     connection->subunit_id = AVRCP_SUBUNIT_ID;
765     big_endian_store_24(connection->cmd_operands, 0, BT_SIG_COMPANY_ID);
766     connection->cmd_operands[3] = AVRCP_PDU_ID_GET_CAPABILITIES; // PDU ID
767     connection->cmd_operands[4] = 0;
768     big_endian_store_16(connection->cmd_operands, 5, 1); // parameter length
769     connection->cmd_operands[7] = capability_id;                  // capability ID
770     connection->cmd_operands_length = 8;
771     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
772     return ERROR_CODE_SUCCESS;
773 }
774 
775 uint8_t avrcp_controller_get_supported_company_ids(uint16_t avrcp_cid){
776     return avrcp_controller_get_capabilities(avrcp_cid, AVRCP_CAPABILITY_ID_COMPANY);
777 }
778 
779 uint8_t avrcp_controller_get_supported_events(uint16_t avrcp_cid){
780     return avrcp_controller_get_capabilities(avrcp_cid, AVRCP_CAPABILITY_ID_EVENT);
781 }
782 
783 
784 uint8_t avrcp_controller_play(uint16_t avrcp_cid){
785     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_PLAY, 0);
786 }
787 
788 uint8_t avrcp_controller_stop(uint16_t avrcp_cid){
789     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_STOP, 0);
790 }
791 
792 uint8_t avrcp_controller_pause(uint16_t avrcp_cid){
793     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_PAUSE, 0);
794 }
795 
796 uint8_t avrcp_controller_forward(uint16_t avrcp_cid){
797     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_FORWARD, 0);
798 }
799 
800 uint8_t avrcp_controller_backward(uint16_t avrcp_cid){
801     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_BACKWARD, 0);
802 }
803 
804 uint8_t avrcp_controller_start_rewind(uint16_t avrcp_cid){
805     return request_continuous_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_REWIND, 0);
806 }
807 
808 uint8_t avrcp_controller_volume_up(uint16_t avrcp_cid){
809     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_VOLUME_UP, 0);
810 }
811 
812 uint8_t avrcp_controller_volume_down(uint16_t avrcp_cid){
813     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_VOLUME_DOWN, 0);
814 }
815 
816 uint8_t avrcp_controller_mute(uint16_t avrcp_cid){
817     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_MUTE, 0);
818 }
819 
820 uint8_t avrcp_controller_skip(uint16_t avrcp_cid){
821     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_SKIP, 0);
822 }
823 
824 uint8_t avrcp_controller_stop_rewind(uint16_t avrcp_cid){
825     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
826     if (!connection){
827         log_error("avrcp_stop_rewind: could not find a connection.");
828         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
829     }
830     if (connection->state != AVCTP_W4_STOP) return ERROR_CODE_COMMAND_DISALLOWED;
831     return request_pass_through_release_control_cmd(connection);
832 }
833 
834 uint8_t avrcp_controller_start_fast_forward(uint16_t avrcp_cid){
835     return request_continuous_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_FAST_FORWARD, 0);
836 }
837 
838 uint8_t avrcp_controller_fast_forward(uint16_t avrcp_cid){
839     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_FAST_FORWARD, 0);
840 }
841 
842 uint8_t avrcp_controller_rewind(uint16_t avrcp_cid){
843     return request_single_pass_through_press_control_cmd(avrcp_cid, AVRCP_OPERATION_ID_REWIND, 0);
844 }
845 
846 
847 uint8_t avrcp_controller_stop_fast_forward(uint16_t avrcp_cid){
848     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
849     if (!connection){
850         log_error("avrcp_stop_fast_forward: could not find a connection.");
851         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
852     }
853     if (connection->state != AVCTP_W4_STOP) return ERROR_CODE_COMMAND_DISALLOWED;
854     return request_pass_through_release_control_cmd(connection);
855 }
856 
857 uint8_t avrcp_controller_get_play_status(uint16_t avrcp_cid){
858     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
859     if (!connection){
860         log_error("avrcp_get_play_status: could not find a connection.");
861         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
862     }
863     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
864     connection->state = AVCTP_W2_SEND_COMMAND;
865     connection->transaction_label++;
866     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
867     connection->command_type = AVRCP_CTYPE_STATUS;
868     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
869     connection->subunit_id = AVRCP_SUBUNIT_ID;
870     big_endian_store_24(connection->cmd_operands, 0, BT_SIG_COMPANY_ID);
871     connection->cmd_operands[3] = AVRCP_PDU_ID_GET_PLAY_STATUS;
872     connection->cmd_operands[4] = 0;                     // reserved(upper 6) | packet_type -> 0
873     big_endian_store_16(connection->cmd_operands, 5, 0); // parameter length
874     connection->cmd_operands_length = 7;
875     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
876     return ERROR_CODE_SUCCESS;
877 }
878 
879 uint8_t avrcp_controller_enable_notification(uint16_t avrcp_cid, avrcp_notification_event_id_t event_id){
880     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
881     if (!connection){
882         log_error("avrcp_get_play_status: could not find a connection.");
883         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
884     }
885     avrcp_register_notification(connection, event_id);
886     return ERROR_CODE_SUCCESS;
887 }
888 
889 uint8_t avrcp_controller_disable_notification(uint16_t avrcp_cid, avrcp_notification_event_id_t event_id){
890     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
891     if (!connection){
892         log_error("avrcp_get_play_status: could not find a connection.");
893         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
894     }
895     connection->notifications_to_deregister |= (1 << event_id);
896     return ERROR_CODE_SUCCESS;
897 }
898 
899 uint8_t avrcp_controller_get_now_playing_info(uint16_t avrcp_cid){
900     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
901     if (!connection){
902         log_error("avrcp_get_capabilities: could not find a connection.");
903         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
904     }
905     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
906     connection->state = AVCTP_W2_SEND_COMMAND;
907 
908     connection->transaction_label++;
909     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
910     connection->command_type = AVRCP_CTYPE_STATUS;
911     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
912     connection->subunit_id = AVRCP_SUBUNIT_ID;
913     int pos = 0;
914     big_endian_store_24(connection->cmd_operands, pos, BT_SIG_COMPANY_ID);
915     pos += 3;
916     connection->cmd_operands[pos++] = AVRCP_PDU_ID_GET_ELEMENT_ATTRIBUTES; // PDU ID
917     connection->cmd_operands[pos++] = 0;
918 
919     // Parameter Length
920     big_endian_store_16(connection->cmd_operands, pos, 9);
921     pos += 2;
922 
923     // write 8 bytes value
924     memset(connection->cmd_operands + pos, 0, 8); // identifier: PLAYING
925     pos += 8;
926 
927     connection->cmd_operands[pos++] = 0; // attribute count, if 0 get all attributes
928     // every attribute is 4 bytes long
929 
930     connection->cmd_operands_length = pos;
931     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
932     return ERROR_CODE_SUCCESS;
933 }
934 
935 uint8_t avrcp_controller_set_absolute_volume(uint16_t avrcp_cid, uint8_t volume){
936      avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
937     if (!connection){
938         log_error("avrcp_get_capabilities: could not find a connection.");
939         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
940     }
941     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
942     connection->state = AVCTP_W2_SEND_COMMAND;
943 
944     connection->transaction_label++;
945     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
946     connection->command_type = AVRCP_CTYPE_CONTROL;
947     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
948     connection->subunit_id = AVRCP_SUBUNIT_ID;
949     int pos = 0;
950     big_endian_store_24(connection->cmd_operands, pos, BT_SIG_COMPANY_ID);
951     pos += 3;
952     connection->cmd_operands[pos++] = AVRCP_PDU_ID_SET_ABSOLUTE_VOLUME; // PDU ID
953     connection->cmd_operands[pos++] = 0;
954 
955     // Parameter Length
956     big_endian_store_16(connection->cmd_operands, pos, 1);
957     pos += 2;
958     connection->cmd_operands[pos++] = volume;
959 
960     connection->cmd_operands_length = pos;
961     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
962     return ERROR_CODE_SUCCESS;
963 }
964 
965 uint8_t avrcp_controller_query_shuffle_and_repeat_modes(uint16_t avrcp_cid){
966     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
967     if (!connection){
968         log_error("avrcp_get_capabilities: could not find a connection.");
969         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
970     }
971     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
972     connection->state = AVCTP_W2_SEND_COMMAND;
973 
974     connection->transaction_label++;
975     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
976     connection->command_type = AVRCP_CTYPE_STATUS;
977     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
978     connection->subunit_id = AVRCP_SUBUNIT_ID;
979     big_endian_store_24(connection->cmd_operands, 0, BT_SIG_COMPANY_ID);
980     connection->cmd_operands[3] = AVRCP_PDU_ID_GetCurrentPlayerApplicationSettingValue; // PDU ID
981     connection->cmd_operands[4] = 0;
982     big_endian_store_16(connection->cmd_operands, 5, 5); // parameter length
983     connection->cmd_operands[7] = 4;                     // NumPlayerApplicationSettingAttributeID
984     // PlayerApplicationSettingAttributeID1 AVRCP Spec, Appendix F, 133
985     connection->cmd_operands[8]  = 0x01;    // equalizer  (1-OFF, 2-ON)
986     connection->cmd_operands[9]  = 0x02;    // repeat     (1-off, 2-single track, 3-all tracks, 4-group repeat)
987     connection->cmd_operands[10] = 0x03;    // shuffle    (1-off, 2-all tracks, 3-group shuffle)
988     connection->cmd_operands[11] = 0x04;    // scan       (1-off, 2-all tracks, 3-group scan)
989     connection->cmd_operands_length = 12;
990     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
991     return ERROR_CODE_SUCCESS;
992 }
993 
994 static uint8_t avrcp_controller_set_current_player_application_setting_value(uint16_t avrcp_cid, uint8_t attr_id, uint8_t attr_value){
995     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
996     if (!connection){
997         log_error("avrcp_get_capabilities: could not find a connection.");
998         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
999     }
1000     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
1001     connection->state = AVCTP_W2_SEND_COMMAND;
1002 
1003     connection->transaction_label++;
1004     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
1005     connection->command_type = AVRCP_CTYPE_CONTROL;
1006     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
1007     connection->subunit_id = AVRCP_SUBUNIT_ID;
1008     int pos = 0;
1009     big_endian_store_24(connection->cmd_operands, pos, BT_SIG_COMPANY_ID);
1010     pos += 3;
1011     connection->cmd_operands[pos++] = AVRCP_PDU_ID_SetPlayerApplicationSettingValue; // PDU ID
1012     connection->cmd_operands[pos++] = 0;
1013     // Parameter Length
1014     big_endian_store_16(connection->cmd_operands, pos, 3);
1015     pos += 2;
1016     connection->cmd_operands[pos++] = 2;
1017     connection->cmd_operands_length = pos;
1018     connection->cmd_operands[pos++]  = attr_id;
1019     connection->cmd_operands[pos++]  = attr_value;
1020     connection->cmd_operands_length = pos;
1021     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
1022     return ERROR_CODE_SUCCESS;
1023 }
1024 
1025 uint8_t avrcp_controller_set_shuffle_mode(uint16_t avrcp_cid, avrcp_shuffle_mode_t mode){
1026     if (mode < AVRCP_SHUFFLE_MODE_OFF || mode > AVRCP_SHUFFLE_MODE_GROUP) return ERROR_CODE_UNSUPPORTED_FEATURE_OR_PARAMETER_VALUE;
1027     return avrcp_controller_set_current_player_application_setting_value(avrcp_cid, 0x03, mode);
1028 }
1029 
1030 uint8_t avrcp_controller_set_repeat_mode(uint16_t avrcp_cid, avrcp_repeat_mode_t mode){
1031     if (mode < AVRCP_REPEAT_MODE_OFF || mode > AVRCP_REPEAT_MODE_GROUP) return ERROR_CODE_UNSUPPORTED_FEATURE_OR_PARAMETER_VALUE;
1032     return avrcp_controller_set_current_player_application_setting_value(avrcp_cid, 0x02, mode);
1033 }
1034 
1035 uint8_t avrcp_controller_disconnect(uint16_t avrcp_cid){
1036     avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_controller_context);
1037     if (!connection){
1038         log_error("avrcp_get_capabilities: could not find a connection.");
1039         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
1040     }
1041     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
1042     l2cap_disconnect(connection->l2cap_signaling_cid, 0);
1043     return ERROR_CODE_SUCCESS;
1044 }