[PATCH v2] Bluetooth: btusb: Configure altsetting for USER_CHANNEL

[Hsin-chen Chuang <chharry@google.com>]

From: Hsin-chen Chuang <chharry@chromium.org>

Automatically configure the altsetting for USER_CHANNEL when a SCO is
connected. This adds support for the USER_CHANNEL to transfer SCO data
over USB transport.

Fixes: b16b327edb4d ("Bluetooth: btusb: add sysfs attribute to control USB alt setting")
Signed-off-by: Hsin-chen Chuang <chharry@chromium.org>
---

Changes in v2:
- Give up tracking the SCO handles. Only configure the altsetting when
  SCO connected.
- Put the change behind Kconfig/module parameter

 drivers/bluetooth/Kconfig | 11 ++++++++++
 drivers/bluetooth/btusb.c | 46 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+)

diff --git a/drivers/bluetooth/Kconfig b/drivers/bluetooth/Kconfig
index 4ab32abf0f48..7c497f878732 100644
--- a/drivers/bluetooth/Kconfig
+++ b/drivers/bluetooth/Kconfig
@@ -56,6 +56,17 @@ config BT_HCIBTUSB_POLL_SYNC
 	  Say Y here to enable USB poll_sync for Bluetooth USB devices by
 	  default.
 
+config BT_HCIBTUSB_AUTO_SET_ISOC_ALT
+	bool "Auto set isoc_altsetting for USER_CHANNEL when SCO connected"
+	depends on BT_HCIBTUSB
+	default n
+	help
+	  Say Y here to enable auto set isoc_altsetting for USER_CHANNEL
+	  when SCO connected
+
+	  This can be overridden by passing btusb.auto_set_isoc_alt=[y|n]
+	  on the kernel commandline.
+
 config BT_HCIBTUSB_BCM
 	bool "Broadcom protocol support"
 	depends on BT_HCIBTUSB
diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index de3fa725d210..af93d757911b 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -34,6 +34,8 @@ static bool force_scofix;
 static bool enable_autosuspend = IS_ENABLED(CONFIG_BT_HCIBTUSB_AUTOSUSPEND);
 static bool enable_poll_sync = IS_ENABLED(CONFIG_BT_HCIBTUSB_POLL_SYNC);
 static bool reset = true;
+static bool auto_set_isoc_alt =
+	IS_ENABLED(CONFIG_BT_HCIBTUSB_AUTO_SET_ISOC_ALT);
 
 static struct usb_driver btusb_driver;
 
@@ -1113,6 +1115,42 @@ static inline void btusb_free_frags(struct btusb_data *data)
 	spin_unlock_irqrestore(&data->rxlock, flags);
 }
 
+static void btusb_sco_connected(struct btusb_data *data, struct sk_buff *skb)
+{
+	struct hci_event_hdr *hdr = (void *) skb->data;
+	struct hci_ev_sync_conn_complete *ev =
+		(void *) skb->data + sizeof(*hdr);
+	struct hci_dev *hdev = data->hdev;
+	unsigned int notify_air_mode;
+
+	if (hci_skb_pkt_type(skb) != HCI_EVENT_PKT)
+		return;
+
+	if (skb->len < sizeof(*hdr) || hdr->evt != HCI_EV_SYNC_CONN_COMPLETE)
+		return;
+
+	if (skb->len != sizeof(*hdr) + sizeof(*ev) || ev->status)
+		return;
+
+	switch (ev->air_mode) {
+	case BT_CODEC_CVSD:
+		notify_air_mode = HCI_NOTIFY_ENABLE_SCO_CVSD;
+		break;
+
+	case BT_CODEC_TRANSPARENT:
+		notify_air_mode = HCI_NOTIFY_ENABLE_SCO_TRANSP;
+		break;
+
+	default:
+		return;
+	}
+
+	bt_dev_info(hdev, "enabling SCO with air mode %u", ev->air_mode);
+	data->sco_num = 1;
+	data->air_mode = notify_air_mode;
+	schedule_work(&data->work);
+}
+
 static int btusb_recv_event(struct btusb_data *data, struct sk_buff *skb)
 {
 	if (data->intr_interval) {
@@ -1120,6 +1158,11 @@ static int btusb_recv_event(struct btusb_data *data, struct sk_buff *skb)
 		schedule_delayed_work(&data->rx_work, 0);
 	}
 
+	/* Configure altsetting for HCI_USER_CHANNEL on SCO connected */
+	if (auto_set_isoc_alt &&
+	    hci_dev_test_flag(data->hdev, HCI_USER_CHANNEL))
+		btusb_sco_connected(data, skb);
+
 	return data->recv_event(data->hdev, skb);
 }
 
@@ -4354,6 +4397,9 @@ MODULE_PARM_DESC(enable_autosuspend, "Enable USB autosuspend by default");
 module_param(reset, bool, 0644);
 MODULE_PARM_DESC(reset, "Send HCI reset command on initialization");
 
+module_param(auto_set_isoc_alt, bool, 0644);
+MODULE_PARM_DESC(auto_set_isoc_alt, "Auto set isoc_altsetting for USER_CHANNEL when SCO connected");
+
 MODULE_AUTHOR("Marcel Holtmann <marcel@holtmann.org>");
 MODULE_DESCRIPTION("Generic Bluetooth USB driver ver " VERSION);
 MODULE_VERSION(VERSION);
-- 
2.48.1.601.g30ceb7b040-goog