Bluetooth: Query LE tx power on startup

Queries tx power via HCI_LE_Read_Transmit_Power command when the hci
device is initialized, and stores resulting min/max LE power in hdev
struct. If command isn't available (< BT5 support), min/max values
both default to HCI_TX_POWER_INVALID.

This patch is manually verified by ensuring BT5 devices correctly query
and receive controller tx power range.

Reviewed-by: Sonny Sasaka <sonnysasaka@chromium.org>
Signed-off-by: Daniel Winkler <danielwinkler@google.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>

include/net/bluetooth/hci.h

@@ -1797,6 +1797,13 @@ struct hci_cp_le_set_adv_set_rand_addr {
 	bdaddr_t  bdaddr;
 } __packed;
 
+#define HCI_OP_LE_READ_TRANSMIT_POWER	0x204b
+struct hci_rp_le_read_transmit_power {
+	__u8  status;
+	__s8  min_le_tx_power;
+	__s8  max_le_tx_power;
+} __packed;
+
 #define HCI_OP_LE_READ_BUFFER_SIZE_V2	0x2060
 struct hci_rp_le_read_buffer_size_v2 {
 	__u8    status;

include/net/bluetooth/hci_core.h

@@ -384,6 +384,8 @@ struct hci_dev {
 	__u16		def_page_timeout;
 	__u16		def_multi_adv_rotation_duration;
 	__u16		def_le_autoconnect_timeout;
+	__s8		min_le_tx_power;
+	__s8		max_le_tx_power;
 
 	__u16		pkt_type;
 	__u16		esco_type;

net/bluetooth/hci_core.c

@@ -741,6 +741,12 @@ static int hci_init3_req(struct hci_request *req, unsigned long opt)
 			hci_req_add(req, HCI_OP_LE_READ_ADV_TX_POWER, 0, NULL);
 		}
 
+		if (hdev->commands[38] & 0x80) {
+			/* Read LE Min/Max Tx Power*/
+			hci_req_add(req, HCI_OP_LE_READ_TRANSMIT_POWER,
+				    0, NULL);
+		}
+
 		if (hdev->commands[26] & 0x40) {
 			/* Read LE White List Size */
 			hci_req_add(req, HCI_OP_LE_READ_WHITE_LIST_SIZE,
@@ -3660,6 +3666,8 @@ struct hci_dev *hci_alloc_dev(void)
 	hdev->le_num_of_adv_sets = HCI_MAX_ADV_INSTANCES;
 	hdev->def_multi_adv_rotation_duration = HCI_DEFAULT_ADV_DURATION;
 	hdev->def_le_autoconnect_timeout = HCI_LE_AUTOCONN_TIMEOUT;
+	hdev->min_le_tx_power = HCI_TX_POWER_INVALID;
+	hdev->max_le_tx_power = HCI_TX_POWER_INVALID;
 
 	hdev->rpa_timeout = HCI_DEFAULT_RPA_TIMEOUT;
 	hdev->discov_interleaved_timeout = DISCOV_INTERLEAVED_TIMEOUT;

net/bluetooth/hci_event.c

@@ -1202,6 +1202,20 @@ static void hci_cc_le_set_adv_set_random_addr(struct hci_dev *hdev,
 	hci_dev_unlock(hdev);
 }
 
+static void hci_cc_le_read_transmit_power(struct hci_dev *hdev,
+					  struct sk_buff *skb)
+{
+	struct hci_rp_le_read_transmit_power *rp = (void *)skb->data;
+
+	BT_DBG("%s status 0x%2.2x", hdev->name, rp->status);
+
+	if (rp->status)
+		return;
+
+	hdev->min_le_tx_power = rp->min_le_tx_power;
+	hdev->max_le_tx_power = rp->max_le_tx_power;
+}
+
 static void hci_cc_le_set_adv_enable(struct hci_dev *hdev, struct sk_buff *skb)
 {
 	__u8 *sent, status = *((__u8 *) skb->data);
@@ -3582,6 +3596,10 @@ static void hci_cmd_complete_evt(struct hci_dev *hdev, struct sk_buff *skb,
 		hci_cc_le_set_adv_set_random_addr(hdev, skb);
 		break;
 
+	case HCI_OP_LE_READ_TRANSMIT_POWER:
+		hci_cc_le_read_transmit_power(hdev, skb);
+		break;
+
 	default:
 		BT_DBG("%s opcode 0x%4.4x", hdev->name, *opcode);
 		break;