xref: /btstack/src/classic/avrcp_browsing_target.c (revision be4cc80ad5308597786dd7d5f87160175907705a)
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_browsing_target.c"
39 
40 #include <stdint.h>
41 #include <stdio.h>
42 #include <stdlib.h>
43 #include <string.h>
44 #include <inttypes.h>
45 #include "btstack.h"
46 #include "classic/avrcp.h"
47 #include "classic/avrcp_browsing_target.h"
48 
49 #define PSM_AVCTP_BROWSING              0x001b
50 
51 static void avrcp_browser_packet_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size, avrcp_context_t * context);
52 static void avrcp_browsing_target_packet_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size);
53 
54 static void avrcp_browsing_target_request_can_send_now(avrcp_browsing_connection_t * connection, uint16_t l2cap_cid){
55     connection->wait_to_send = 1;
56     l2cap_request_can_send_now_event(l2cap_cid);
57 }
58 
59 static int avrcp_browsing_target_handle_can_send_now(avrcp_browsing_connection_t * connection){
60     int pos = 0;
61     // printf("avrcp_browsing_target_handle_can_send_now, cmd_operands_length %d\n", connection->cmd_operands_length);
62     // printf_hexdump(connection->cmd_operands, connection->cmd_operands_length);
63 
64     // l2cap_reserve_packet_buffer();
65     // uint8_t * packet = l2cap_get_outgoing_buffer();
66     uint8_t packet[300];
67     connection->packet_type = AVRCP_SINGLE_PACKET;
68 
69     packet[pos++] = (connection->transaction_label << 4) | (connection->packet_type << 2) | (AVRCP_RESPONSE_FRAME << 1) | 0;
70     // Profile IDentifier (PID)
71     packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL >> 8;
72     packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL & 0x00FF;
73     (void)memcpy(packet + pos, connection->cmd_operands,
74                  connection->cmd_operands_length);
75 
76     pos += connection->cmd_operands_length;
77     connection->wait_to_send = 0;
78     // return l2cap_send_prepared(connection->l2cap_browsing_cid, pos);
79     return l2cap_send(connection->l2cap_browsing_cid, packet, pos);
80 }
81 
82 
83 static uint8_t avrcp_browsing_target_response_general_reject(avrcp_browsing_connection_t * connection, avrcp_status_code_t status){
84     // AVRCP_CTYPE_RESPONSE_REJECTED
85     int pos = 0;
86     connection->cmd_operands[pos++] = AVRCP_PDU_ID_GENERAL_REJECT;
87     // connection->cmd_operands[pos++] = 0;
88     // param length
89     big_endian_store_16(connection->cmd_operands, pos, 1);
90     pos += 2;
91     connection->cmd_operands[pos++] = status;
92     connection->cmd_operands_length = 4;
93     connection->state = AVCTP_W2_SEND_RESPONSE;
94     avrcp_browsing_target_request_can_send_now(connection, connection->l2cap_browsing_cid);
95     return ERROR_CODE_SUCCESS;
96 }
97 
98 static void avrcp_browsing_target_emit_get_folder_items(btstack_packet_handler_t callback, uint16_t browsing_cid, avrcp_browsing_connection_t * connection){
99     btstack_assert(callback != NULL);
100 
101     uint8_t event[10];
102     int pos = 0;
103     event[pos++] = HCI_EVENT_AVRCP_META;
104     event[pos++] = sizeof(event) - 2;
105     event[pos++] = AVRCP_SUBEVENT_BROWSING_GET_FOLDER_ITEMS;
106     little_endian_store_16(event, pos, browsing_cid);
107     pos += 2;
108     event[pos++] = connection->scope;
109     big_endian_store_32(event, pos, connection->attr_bitmap);
110     pos += 4;
111     (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
112 }
113 
114 static void avrcp_browsing_target_emit_get_total_num_items(btstack_packet_handler_t callback, uint16_t browsing_cid, avrcp_browsing_connection_t * connection){
115     btstack_assert(callback != NULL);
116 
117     uint8_t event[10];
118     int pos = 0;
119     event[pos++] = HCI_EVENT_AVRCP_META;
120     event[pos++] = sizeof(event) - 2;
121     event[pos++] = AVRCP_SUBEVENT_BROWSING_GET_TOTAL_NUM_ITEMS;
122     little_endian_store_16(event, pos, browsing_cid);
123     pos += 2;
124     event[pos++] = connection->scope;
125     (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
126 }
127 
128 static void avrcp_emit_browsing_connection_established(btstack_packet_handler_t callback, uint16_t browsing_cid, bd_addr_t addr, uint8_t status){
129     btstack_assert(callback != NULL);
130 
131     uint8_t event[12];
132     int pos = 0;
133     event[pos++] = HCI_EVENT_AVRCP_META;
134     event[pos++] = sizeof(event) - 2;
135     event[pos++] = AVRCP_SUBEVENT_BROWSING_CONNECTION_ESTABLISHED;
136     event[pos++] = status;
137     reverse_bd_addr(addr,&event[pos]);
138     pos += 6;
139     little_endian_store_16(event, pos, browsing_cid);
140     pos += 2;
141     (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
142 }
143 
144 static void avrcp_emit_incoming_browsing_connection(btstack_packet_handler_t callback, uint16_t browsing_cid, bd_addr_t addr){
145     btstack_assert(callback != NULL);
146 
147     uint8_t event[11];
148     int pos = 0;
149     event[pos++] = HCI_EVENT_AVRCP_META;
150     event[pos++] = sizeof(event) - 2;
151     event[pos++] = AVRCP_SUBEVENT_INCOMING_BROWSING_CONNECTION;
152     reverse_bd_addr(addr,&event[pos]);
153     pos += 6;
154     little_endian_store_16(event, pos, browsing_cid);
155     pos += 2;
156     (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
157 }
158 
159 static void avrcp_emit_browsing_connection_closed(btstack_packet_handler_t callback, uint16_t browsing_cid){
160     btstack_assert(callback != NULL);
161 
162     uint8_t event[5];
163     int pos = 0;
164     event[pos++] = HCI_EVENT_AVRCP_META;
165     event[pos++] = sizeof(event) - 2;
166     event[pos++] = AVRCP_SUBEVENT_BROWSING_CONNECTION_RELEASED;
167     little_endian_store_16(event, pos, browsing_cid);
168     pos += 2;
169     (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
170 }
171 
172 static avrcp_browsing_connection_t * avrcp_browsing_create_connection(avrcp_connection_t * avrcp_connection){
173     avrcp_browsing_connection_t * connection = btstack_memory_avrcp_browsing_connection_get();
174     connection->state = AVCTP_CONNECTION_IDLE;
175     connection->transaction_label = 0xFF;
176     avrcp_connection->avrcp_browsing_cid = avrcp_get_next_cid(avrcp_connection->role);
177     avrcp_connection->browsing_connection = connection;
178     return connection;
179 }
180 
181 static uint8_t avrcp_browsing_connect(bd_addr_t remote_addr, avrcp_context_t * context, uint8_t * ertm_buffer, uint32_t size, l2cap_ertm_config_t * ertm_config, uint16_t * browsing_cid){
182     avrcp_connection_t * avrcp_connection = get_avrcp_connection_for_bd_addr_for_role(context->role, remote_addr);
183 
184     if (!avrcp_connection){
185         log_error("avrcp: there is no previously established AVRCP controller connection.");
186         return ERROR_CODE_COMMAND_DISALLOWED;
187     }
188 
189     avrcp_browsing_connection_t * connection = avrcp_connection->browsing_connection;
190     if (connection){
191         log_error(" avrcp_browsing_connect connection exists.");
192         return ERROR_CODE_SUCCESS;
193     }
194 
195     connection = avrcp_browsing_create_connection(avrcp_connection);
196     if (!connection){
197         log_error("avrcp: could not allocate connection struct.");
198         return BTSTACK_MEMORY_ALLOC_FAILED;
199     }
200 
201     if (browsing_cid){
202         *browsing_cid = avrcp_connection->avrcp_browsing_cid;
203     }
204 
205     connection->ertm_buffer = ertm_buffer;
206     connection->ertm_buffer_size = size;
207     avrcp_connection->browsing_connection = connection;
208 
209     (void)memcpy(&connection->ertm_config, ertm_config,
210                  sizeof(l2cap_ertm_config_t));
211 
212     return l2cap_create_ertm_channel(avrcp_browsing_target_packet_handler, remote_addr, avrcp_connection->browsing_l2cap_psm,
213                     &connection->ertm_config, connection->ertm_buffer, connection->ertm_buffer_size, NULL);
214 
215 }
216 
217 static void avrcp_browser_packet_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size, avrcp_context_t * context){
218     UNUSED(channel);
219     UNUSED(size);
220     bd_addr_t event_addr;
221     uint16_t local_cid;
222     uint8_t  status;
223     avrcp_browsing_connection_t * browsing_connection = NULL;
224     avrcp_connection_t * avrcp_connection = NULL;
225 
226     if (packet_type != HCI_EVENT_PACKET) return;
227 
228     switch (hci_event_packet_get_type(packet)) {
229         case HCI_EVENT_DISCONNECTION_COMPLETE:
230             avrcp_emit_browsing_connection_closed(context->browsing_avrcp_callback, 0);
231             break;
232         case L2CAP_EVENT_INCOMING_CONNECTION:
233             l2cap_event_incoming_connection_get_address(packet, event_addr);
234             local_cid = l2cap_event_incoming_connection_get_local_cid(packet);
235             avrcp_connection = get_avrcp_connection_for_bd_addr_for_role(context->role, event_addr);
236             if (!avrcp_connection) {
237                 log_error("No previously created AVRCP controller connections");
238                 l2cap_decline_connection(local_cid);
239                 break;
240             }
241             browsing_connection = avrcp_browsing_create_connection(avrcp_connection);
242             browsing_connection->l2cap_browsing_cid = local_cid;
243             browsing_connection->state = AVCTP_CONNECTION_W4_ERTM_CONFIGURATION;
244             log_info("Emit AVRCP_SUBEVENT_INCOMING_BROWSING_CONNECTION browsing_cid 0x%02x, l2cap_signaling_cid 0x%02x\n", avrcp_connection->avrcp_browsing_cid, browsing_connection->l2cap_browsing_cid);
245             avrcp_emit_incoming_browsing_connection(context->browsing_avrcp_callback, avrcp_connection->avrcp_browsing_cid, event_addr);
246             break;
247 
248         case L2CAP_EVENT_CHANNEL_OPENED:
249             l2cap_event_channel_opened_get_address(packet, event_addr);
250             status = l2cap_event_channel_opened_get_status(packet);
251             local_cid = l2cap_event_channel_opened_get_local_cid(packet);
252 
253             avrcp_connection = get_avrcp_connection_for_bd_addr_for_role(context->role, event_addr);
254             if (!avrcp_connection){
255                 log_error("Failed to find AVRCP connection for bd_addr %s", bd_addr_to_str(event_addr));
256                 avrcp_emit_browsing_connection_established(context->browsing_avrcp_callback, local_cid, event_addr, L2CAP_LOCAL_CID_DOES_NOT_EXIST);
257                 l2cap_disconnect(local_cid, 0); // reason isn't used
258                 break;
259             }
260 
261             browsing_connection = avrcp_connection->browsing_connection;
262             if (status != ERROR_CODE_SUCCESS){
263                 log_info("L2CAP connection to connection %s failed. status code 0x%02x", bd_addr_to_str(event_addr), status);
264                 avrcp_emit_browsing_connection_established(context->browsing_avrcp_callback, avrcp_connection->avrcp_browsing_cid, event_addr, status);
265                 btstack_memory_avrcp_browsing_connection_free(browsing_connection);
266                 avrcp_connection->browsing_connection = NULL;
267                 break;
268             }
269             if (browsing_connection->state != AVCTP_CONNECTION_W4_L2CAP_CONNECTED) break;
270 
271             browsing_connection->l2cap_browsing_cid = local_cid;
272 
273             log_info("L2CAP_EVENT_CHANNEL_OPENED browsing cid 0x%02x, l2cap cid 0x%02x", avrcp_connection->avrcp_browsing_cid, browsing_connection->l2cap_browsing_cid);
274             browsing_connection->state = AVCTP_CONNECTION_OPENED;
275             avrcp_emit_browsing_connection_established(context->browsing_avrcp_callback, avrcp_connection->avrcp_browsing_cid, event_addr, ERROR_CODE_SUCCESS);
276             break;
277 
278         case L2CAP_EVENT_CHANNEL_CLOSED:
279             local_cid = l2cap_event_channel_closed_get_local_cid(packet);
280             avrcp_connection = get_avrcp_connection_for_browsing_l2cap_cid_for_role(context->role, local_cid);
281 
282             if (avrcp_connection && avrcp_connection->browsing_connection){
283                 avrcp_emit_browsing_connection_closed(context->browsing_avrcp_callback, avrcp_connection->avrcp_browsing_cid);
284                 // free connection
285                 btstack_memory_avrcp_browsing_connection_free(avrcp_connection->browsing_connection);
286                 avrcp_connection->browsing_connection = NULL;
287                 break;
288             }
289             break;
290         default:
291             break;
292     }
293 }
294 
295 
296 static void avrcp_browsing_target_packet_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
297     avrcp_browsing_connection_t * browsing_connection;
298 
299     switch (packet_type) {
300         case L2CAP_DATA_PACKET:{
301             browsing_connection = get_avrcp_browsing_connection_for_l2cap_cid_for_role(AVRCP_TARGET, channel);
302             if (!browsing_connection) break;
303             int pos = 0;
304             uint8_t transport_header = packet[pos++];
305             // Transaction label | Packet_type | C/R | IPID (1 == invalid profile identifier)
306             browsing_connection->transaction_label = transport_header >> 4;
307             avrcp_packet_type_t avctp_packet_type = (transport_header & 0x0F) >> 2;
308             switch (avctp_packet_type){
309                 case AVRCP_SINGLE_PACKET:
310                 case AVRCP_START_PACKET:
311                     browsing_connection->subunit_type = packet[pos++] >> 2;
312                     browsing_connection->subunit_id = 0;
313                     browsing_connection->command_opcode = packet[pos++];
314                     browsing_connection->num_packets = 1;
315                     if (avctp_packet_type == AVRCP_START_PACKET){
316                         browsing_connection->num_packets = packet[pos++];
317                     }
318                     browsing_connection->pdu_id = packet[pos++];
319                     break;
320                 default:
321                     break;
322             }
323             switch (avctp_packet_type){
324                 case AVRCP_SINGLE_PACKET:
325                 case AVRCP_END_PACKET:
326                     switch(browsing_connection->pdu_id){
327                         case AVRCP_PDU_ID_GET_FOLDER_ITEMS:
328                             printf("\n");
329                             browsing_connection->scope = packet[pos++];
330                             browsing_connection->start_item = big_endian_read_32(packet, pos);
331                             pos += 4;
332                             browsing_connection->end_item = big_endian_read_32(packet, pos);
333                             pos += 4;
334                             uint8_t attr_count = packet[pos++];
335 
336                             while (attr_count){
337                                 uint32_t attr_id = big_endian_read_32(packet, pos);
338                                 pos += 4;
339                                 browsing_connection->attr_bitmap |= (1 << attr_id);
340                                 attr_count--;
341                             }
342                             avrcp_browsing_target_emit_get_folder_items(avrcp_target_context.browsing_avrcp_callback, channel, browsing_connection);
343                             break;
344                         case AVRCP_PDU_ID_GET_TOTAL_NUMBER_OF_ITEMS:{
345                             // send total num items
346                             browsing_connection->scope = packet[pos++];
347                             avrcp_browsing_target_emit_get_total_num_items(avrcp_target_context.browsing_avrcp_callback, channel, browsing_connection);
348                             break;
349                         }
350                         default:
351                             avrcp_browsing_target_response_general_reject(browsing_connection, AVRCP_STATUS_INVALID_COMMAND);
352                             log_info(" not parsed pdu ID 0x%02x", browsing_connection->pdu_id);
353                             break;
354                     }
355                     browsing_connection->state = AVCTP_CONNECTION_OPENED;
356                     break;
357                 default:
358                     break;
359             }
360             break;
361         }
362 
363         case HCI_EVENT_PACKET:
364             switch (hci_event_packet_get_type(packet)){
365                 case L2CAP_EVENT_CAN_SEND_NOW:
366                     browsing_connection = get_avrcp_browsing_connection_for_l2cap_cid_for_role(AVRCP_TARGET, channel);
367                     if (!browsing_connection) break;
368                     if (browsing_connection->state != AVCTP_W2_SEND_RESPONSE) return;
369                     browsing_connection->state = AVCTP_CONNECTION_OPENED;
370                     avrcp_browsing_target_handle_can_send_now(browsing_connection);
371                     break;
372                 default:
373                     avrcp_browser_packet_handler(packet_type, channel, packet, size, &avrcp_target_context);
374                     break;
375             }
376             break;
377 
378         default:
379             break;
380     }
381 }
382 
383 void avrcp_browsing_target_init(void){
384     avrcp_target_context.browsing_packet_handler = avrcp_browsing_target_packet_handler;
385     l2cap_register_service(&avrcp_browsing_target_packet_handler, PSM_AVCTP_BROWSING, 0xffff, gap_get_security_level());
386 }
387 
388 void avrcp_browsing_target_register_packet_handler(btstack_packet_handler_t callback){
389     btstack_assert(callback != NULL);
390     avrcp_target_context.browsing_avrcp_callback = callback;
391 }
392 
393 uint8_t avrcp_browsing_target_connect(bd_addr_t bd_addr, uint8_t * ertm_buffer, uint32_t size, l2cap_ertm_config_t * ertm_config, uint16_t * avrcp_browsing_cid){
394     return avrcp_browsing_connect(bd_addr, &avrcp_target_context, ertm_buffer, size, ertm_config, avrcp_browsing_cid);
395 }
396 
397 uint8_t avrcp_browsing_target_disconnect(uint16_t avrcp_browsing_cid){
398     avrcp_connection_t * avrcp_connection = get_avrcp_connection_for_browsing_cid_for_role(AVRCP_TARGET, avrcp_browsing_cid);
399     if (!avrcp_connection){
400         log_error("avrcp_browsing_target_disconnect: could not find a connection.");
401         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
402     }
403     if (avrcp_connection->browsing_connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
404 
405     l2cap_disconnect(avrcp_connection->browsing_connection->l2cap_browsing_cid, 0);
406     return ERROR_CODE_SUCCESS;
407 }
408 
409 uint8_t avrcp_browsing_target_configure_incoming_connection(uint16_t avrcp_browsing_cid, uint8_t * ertm_buffer, uint32_t size, l2cap_ertm_config_t * ertm_config){
410     avrcp_connection_t * avrcp_connection = get_avrcp_connection_for_browsing_cid_for_role(AVRCP_TARGET, avrcp_browsing_cid);
411     if (!avrcp_connection){
412         log_error("avrcp_browsing_decline_incoming_connection: could not find a connection.");
413         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
414     }
415     if (!avrcp_connection->browsing_connection){
416         log_error("avrcp_browsing_decline_incoming_connection: no browsing connection.");
417         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
418     }
419 
420     if (avrcp_connection->browsing_connection->state != AVCTP_CONNECTION_W4_ERTM_CONFIGURATION){
421         log_error("avrcp_browsing_decline_incoming_connection: browsing connection in a wrong state.");
422         return ERROR_CODE_COMMAND_DISALLOWED;
423     }
424 
425     avrcp_connection->browsing_connection->state = AVCTP_CONNECTION_W4_L2CAP_CONNECTED;
426     avrcp_connection->browsing_connection->ertm_buffer = ertm_buffer;
427     avrcp_connection->browsing_connection->ertm_buffer_size = size;
428     (void)memcpy(&avrcp_connection->browsing_connection->ertm_config,
429                  ertm_config, sizeof(l2cap_ertm_config_t));
430     l2cap_accept_ertm_connection(avrcp_connection->browsing_connection->l2cap_browsing_cid, &avrcp_connection->browsing_connection->ertm_config, avrcp_connection->browsing_connection->ertm_buffer, avrcp_connection->browsing_connection->ertm_buffer_size);
431     return ERROR_CODE_SUCCESS;
432 }
433 
434 uint8_t avrcp_browsing_target_decline_incoming_connection(uint16_t avrcp_browsing_cid){
435     avrcp_connection_t * avrcp_connection = get_avrcp_connection_for_browsing_cid_for_role(AVRCP_TARGET, avrcp_browsing_cid);
436     if (!avrcp_connection){
437         log_error("avrcp_browsing_decline_incoming_connection: could not find a connection.");
438         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
439     }
440     if (!avrcp_connection->browsing_connection) return ERROR_CODE_SUCCESS;
441     if (avrcp_connection->browsing_connection->state > AVCTP_CONNECTION_W4_ERTM_CONFIGURATION) return ERROR_CODE_COMMAND_DISALLOWED;
442 
443     l2cap_decline_connection(avrcp_connection->browsing_connection->l2cap_browsing_cid);
444     // free connection
445     btstack_memory_avrcp_browsing_connection_free(avrcp_connection->browsing_connection);
446     avrcp_connection->browsing_connection = NULL;
447     return ERROR_CODE_SUCCESS;
448 }
449 
450 uint8_t avrcp_subevent_browsing_get_folder_items_response(uint16_t avrcp_browsing_cid, uint16_t uid_counter, uint8_t * attr_list, uint16_t attr_list_size){
451     avrcp_connection_t * avrcp_connection = get_avrcp_connection_for_browsing_cid_for_role(AVRCP_TARGET, avrcp_browsing_cid);
452     if (!avrcp_connection){
453         log_error("avrcp_browsing_controller_disconnect: could not find a connection.");
454         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
455     }
456 
457     avrcp_browsing_connection_t * connection = avrcp_connection->browsing_connection;
458     if (!connection){
459         log_info("avrcp_subevent_browsing_get_folder_items_response: could not find a connection.");
460         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
461     }
462     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
463 
464     if (connection->state != AVCTP_CONNECTION_OPENED) {
465         log_info("avrcp_subevent_browsing_get_folder_items_response: wrong state.");
466         return ERROR_CODE_COMMAND_DISALLOWED;
467     }
468     int pos = 0;
469 
470     connection->cmd_operands[pos++] = AVRCP_PDU_ID_GET_FOLDER_ITEMS;
471     big_endian_store_16(connection->cmd_operands, pos, attr_list_size);
472     pos += 2;
473 
474     connection->cmd_operands[pos++] = AVRCP_STATUS_SUCCESS;
475     big_endian_store_16(connection->cmd_operands, pos, uid_counter);
476     pos += 2;
477 
478     // TODO: fragmentation
479     if (attr_list_size >  sizeof(connection->cmd_operands)){
480         connection->attr_list = attr_list;
481         connection->attr_list_size = attr_list_size;
482         log_info(" todo: list too big, invoke fragmentation");
483         return 1;
484     }
485     (void)memcpy(&connection->cmd_operands[pos], attr_list, attr_list_size);
486     pos += attr_list_size;
487     connection->cmd_operands_length = pos;
488     // printf_hexdump(connection->cmd_operands, connection->cmd_operands_length);
489 
490     connection->state = AVCTP_W2_SEND_RESPONSE;
491     avrcp_browsing_target_request_can_send_now(connection, connection->l2cap_browsing_cid);
492     return ERROR_CODE_SUCCESS;
493 }
494 
495 
496 uint8_t avrcp_subevent_browsing_get_total_num_items_response(uint16_t avrcp_browsing_cid, uint16_t uid_counter, uint32_t total_num_items){
497     avrcp_connection_t * avrcp_connection = get_avrcp_connection_for_browsing_cid_for_role(AVRCP_TARGET, avrcp_browsing_cid);
498     if (!avrcp_connection){
499         log_error("avrcp_browsing_controller_disconnect: could not find a connection.");
500         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
501     }
502 
503     avrcp_browsing_connection_t * connection = avrcp_connection->browsing_connection;
504     if (!connection){
505         log_info("avrcp_subevent_browsing_get_folder_items_response: could not find a connection.");
506         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
507     }
508     if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
509 
510     if (connection->state != AVCTP_CONNECTION_OPENED) {
511         log_info("avrcp_subevent_browsing_get_folder_items_response: wrong state.");
512         return ERROR_CODE_COMMAND_DISALLOWED;
513     }
514 
515     int pos = 0;
516     connection->cmd_operands[pos++] = AVRCP_PDU_ID_GET_TOTAL_NUMBER_OF_ITEMS;
517     big_endian_store_16(connection->cmd_operands, pos, 7);
518     pos += 2;
519     connection->cmd_operands[pos++] = AVRCP_STATUS_SUCCESS;
520     big_endian_store_16(connection->cmd_operands, pos, uid_counter);
521     pos += 2;
522     big_endian_store_32(connection->cmd_operands, pos, total_num_items);
523     pos += 4;
524     connection->cmd_operands_length = pos;
525 
526     connection->state = AVCTP_W2_SEND_RESPONSE;
527     avrcp_browsing_target_request_can_send_now(connection, connection->l2cap_browsing_cid);
528     return ERROR_CODE_SUCCESS;
529 }
530 
531