Commit ed2ea2c7 authored by Asbjørn Sæbø's avatar Asbjørn Sæbø Committed by Carles Cufi
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Bluetooth: Audio: Media - truncate strings for notification 



Truncate strings being notified to fit the ATT_MTU, to prevent
notifications from not being delivered due to being too long.

For now uses the minimum ATT_MTU, as the MCS does not yet track
connections.

Signed-off-by: default avatarAsbjørn Sæbø <asbjorn.sabo@nordicsemi.no>
parent 2ec32224

subsys/bluetooth/audio/Kconfig.mcs

+1 −0
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ 
config BT_MCS

	bool "Media Control Service Support"

	depends on MCTL_LOCAL_PLAYER_REMOTE_CONTROL

	depends on UTF8

	select BT_CCID

	select EXPERIMENTAL

	help

subsys/bluetooth/audio/mcs.c

+34 −2
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 
#include <init.h>

#include <stdio.h>

#include <zephyr/types.h>

#include <sys/util.h>



#include <bluetooth/bluetooth.h>

#include <bluetooth/conn.h>
@@ -794,7 +795,7 @@ struct bt_ots *bt_mcs_get_ots(void) 
/* Callback functions from the media player, notifying attributes */

/* Placed here, after the service definition, because they reference it. */



/* Helper function to shorten functions that notify */

/* Helper function to notify non-string values */

static void notify(const struct bt_uuid *uuid, const void *data, uint16_t len)

{

	int err = bt_gatt_notify_uuid(NULL, uuid, mcs.attrs, data, len);
@@ -808,6 +809,37 @@ static void notify(const struct bt_uuid *uuid, const void *data, uint16_t len) 
	}

}



/* Helper function to notify UTF8 string values

 * Will truncate string to fit within notification if required.

 * The string must be null-terminated.

 */

static void notify_string(const struct bt_uuid *uuid, const char *str)

{

	/* TODO:

	 * This function will need to get the ATT_MTU to know what length to

	 * truncate the string to.  But the ATT_MTU is per connection, and MCS

	 * is not connection-aware yet.

	 * For now: Truncate according to the default ATT_MTU, so that

	 * notifications will go through

	 */



	/* TODO: Use bt_gatt_get_mtu() to find the ATT_MTU */

	const uint16_t att_mtu = 23;

	const uint16_t maxlen = att_mtu - 1 - 2; /* Subtract opcode and handle */

	const uint16_t len = strlen(str);



	if (len > maxlen) {

		/* Truncation requires, and gives, a null-terminated string. */

		char trunc_str[maxlen + 1];



		utf8_lcpy(trunc_str, str, sizeof(trunc_str));

		/* Null-termination is not sent on air */

		notify(uuid, (void *)trunc_str, strlen(trunc_str));

	} else {

		notify(uuid, (void *)str, len);

	}

}



void media_proxy_sctrl_track_changed_cb(void)

{

	BT_DBG("Notifying track change");
@@ -817,7 +849,7 @@ void media_proxy_sctrl_track_changed_cb(void) 
void media_proxy_sctrl_track_title_cb(const char *title)

{

	BT_DBG("Notifying track title: %s", log_strdup(title));

	notify(BT_UUID_MCS_TRACK_TITLE, title, strlen(title));

	notify_string(BT_UUID_MCS_TRACK_TITLE, title);

}



void media_proxy_sctrl_track_position_cb(int32_t position)

tests/bluetooth/bsim_bt/bsim_test_audio/prj.conf

+1 −0
Original line number Diff line number Diff line
@@ -66,6 +66,7 @@ CONFIG_MCTL_LOCAL_PLAYER_LOCAL_CONTROL=y 
CONFIG_MCTL_LOCAL_PLAYER_REMOTE_CONTROL=y

CONFIG_MCTL_REMOTE_PLAYER_CONTROL=y

CONFIG_MCTL_REMOTE_PLAYER_CONTROL_OBJECTS=y

CONFIG_UTF8=y



# Media player

CONFIG_BT_MPL=y

tests/bluetooth/shell/audio.conf

+1 −0
Original line number Diff line number Diff line
@@ -87,6 +87,7 @@ CONFIG_BT_MCS=y 
CONFIG_BT_MCC=y

CONFIG_BT_MCC_OTS=y

CONFIG_BT_MCC_TOTAL_OBJ_CONTENT_MEM=4096

CONFIG_UTF8=y



# Object Transfer

CONFIG_BT_OTS=y

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