bluetooth: host: Add a check for num of bt_conn_tx and ACL/ISO bufs

After #72090, each
packet to be sent (wether ACL or ISO data) has a corresponding
`bt_conn_tx` object, regardless of whether a callback is used.

This means that number of packets Host can send to Controller is limited
by the smaller of two values: ACL/ISO packets Controller can receive,
and the number of `bt_conn_tx` objects allocated by Host.

A mismatch between these numbers may lead to inefficient resource usage
on either Host or Controller side. If Host allocates fewer `bt_conn_tx`
objects than the number of buffers available on Controller for a given
data type, some Controller buffers may go unused. Conversely, if Host
allocates more `bt_conn_tx` objects than Controller can consume, the
excess objects remain unused.

This commit adds a check and issues a warning if the number of
`bt_conn_tx` objects is not aligned with the number of ACL/ISO buffers
reported by Controller via the LE Read Buffer Size v1 or v2 command.

Signed-off-by: Pavel Vasilyev <pavel.vasilyev@nordicsemi.no>

Author: PavelVPV

subsys/bluetooth/host/hci_core.c

@@ -92,6 +92,26 @@ BUILD_ASSERT(IS_ENABLED(CONFIG_ZTEST), "Missing DT chosen property for HCI");
 #define BT_HCI_QUIRKS 0
 #endif
 
+/* These checks are added to warn if the number of ACL or ISO packets in Controller is not equal to
+ * the number of bt_conn_tx contexts allocated by Host. The inequality of these two values can lead
+ * to inefficient resources usage either on Host's or Controller's side.
+ */
+#define CHECK_NUM_OF_ACL_PKTS(_num) \
+	do { \
+		if (CONFIG_BT_BUF_ACL_TX_COUNT != (_num)) { \
+			LOG_WRN("Num of Controller's ACL packets != ACL bt_conn_tx contexts" \
+				" (%u != %u)", (_num), CONFIG_BT_BUF_ACL_TX_COUNT); \
+		} \
+	} while (0)
+
+#define CHECK_NUM_OF_ISO_PKTS(_num) \
+	do { \
+		if (CONFIG_BT_ISO_TX_BUF_COUNT != (_num)) { \
+			LOG_WRN("Num of Controller's ISO packets != ISO bt_conn_tx contexts" \
+				"(%u != %u)", (_num), CONFIG_BT_ISO_TX_BUF_COUNT); \
+		} \
+	} while (0)
+
 void bt_tx_irq_raise(void);
 
 #define HCI_CMD_TIMEOUT      K_SECONDS(10)
@@ -3145,6 +3165,8 @@ static void le_read_buffer_size_complete(struct net_buf *buf)
 
 	LOG_DBG("ACL LE buffers: pkts %u mtu %u", rp->le_max_num, bt_dev.le.acl_mtu);
 
+	CHECK_NUM_OF_ACL_PKTS(rp->le_max_num);
+
 	k_sem_init(&bt_dev.le.acl_pkts, rp->le_max_num, rp->le_max_num);
 #endif /* CONFIG_BT_CONN */
 }
@@ -3164,6 +3186,8 @@ static void read_buffer_size_v2_complete(struct net_buf *buf)
 		LOG_DBG("ACL LE buffers: pkts %u mtu %u", rp->acl_max_num, bt_dev.le.acl_mtu);
 
 		k_sem_init(&bt_dev.le.acl_pkts, rp->acl_max_num, rp->acl_max_num);
+
+		CHECK_NUM_OF_ACL_PKTS(rp->acl_max_num);
 	}
 #endif /* CONFIG_BT_CONN */
 
@@ -3180,6 +3204,8 @@ static void read_buffer_size_v2_complete(struct net_buf *buf)
 
 	k_sem_init(&bt_dev.le.iso_pkts, rp->iso_max_num, rp->iso_max_num);
 	bt_dev.le.iso_limit = rp->iso_max_num;
+
+	CHECK_NUM_OF_ISO_PKTS(rp->iso_max_num);
 #endif /* CONFIG_BT_ISO */
 }