When a Bluetooth raw socket is open, the HCI event related to SCO
connection changes are not dispatched to the hci_event module, and
the underlying Bluetooth controller's USB Interface 1 will not be
updated accordingly.

This patch adds `isoc_alt` sysfs attribute, allowing user space
to update the alternate setting of the USB interface alternate
setting as needed.

Signed-off-by: Ying Hsu <yinghsu@chromium.org>
---
This commit has been tested on a chromebook with AX211.

Changes in v2:
- Add check for the existence of a valid USB interface 1.

 drivers/bluetooth/btusb.c | 34 +++++++++++++++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index 279fe6c115fa..7d7cfcd07aef 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -3645,6 +3645,32 @@ static const struct file_operations force_poll_sync_fops = {
 	.llseek		= default_llseek,
 };
 
+static ssize_t isoc_alt_show(struct device *dev,
+			     struct device_attribute *attr,
+			     char *buf)
+{
+	struct btusb_data *data = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "%d\n", data->isoc_altsetting);
+}
+
+static ssize_t isoc_alt_store(struct device *dev,
+			      struct device_attribute *attr,
+			      const char *buf, size_t count)
+{
+	struct btusb_data *data = dev_get_drvdata(dev);
+	int alt;
+	int ret;
+
+	if (kstrtoint(buf, 10, &alt))
+		return -EINVAL;
+
+	ret = btusb_switch_alt_setting(data->hdev, alt);
+	return ret < 0 ? ret : count;
+}
+
+static DEVICE_ATTR_RW(isoc_alt);
+
 static int btusb_probe(struct usb_interface *intf,
 		       const struct usb_device_id *id)
 {
@@ -4008,6 +4034,10 @@ static int btusb_probe(struct usb_interface *intf,
 						 data->isoc, data);
 		if (err < 0)
 			goto out_free_dev;
+
+		err = device_create_file(&intf->dev, &dev_attr_isoc_alt);
+		if (err)
+			goto out_free_dev;
 	}
 
 	if (IS_ENABLED(CONFIG_BT_HCIBTUSB_BCM) && data->diag) {
@@ -4054,8 +4084,10 @@ static void btusb_disconnect(struct usb_interface *intf)
 	hdev = data->hdev;
 	usb_set_intfdata(data->intf, NULL);
 
-	if (data->isoc)
+	if (data->isoc) {
+		device_remove_file(&intf->dev, &dev_attr_isoc_alt);
 		usb_set_intfdata(data->isoc, NULL);
+	}
 
 	if (data->diag)
 		usb_set_intfdata(data->diag, NULL);
-- 
2.47.1.613.gc27f4b7a9f-goog

On Fri, Dec 13, 2024 at 12:04:22PM +0800, Ying Hsu wrote:
> When a Bluetooth raw socket is open, the HCI event related to SCO
> connection changes are not dispatched to the hci_event module, and
> the underlying Bluetooth controller's USB Interface 1 will not be
> updated accordingly.
> 
> This patch adds `isoc_alt` sysfs attribute, allowing user space
> to update the alternate setting of the USB interface alternate
> setting as needed.
> 
> Signed-off-by: Ying Hsu <yinghsu@chromium.org>
> ---
> This commit has been tested on a chromebook with AX211.
> 
> Changes in v2:
> - Add check for the existence of a valid USB interface 1.

You forgot a Documentation/ABI/ entry.

Also, the code isn't quite right:

> @@ -4008,6 +4034,10 @@ static int btusb_probe(struct usb_interface *intf,
>  						 data->isoc, data);
>  		if (err < 0)
>  			goto out_free_dev;
> +
> +		err = device_create_file(&intf->dev, &dev_attr_isoc_alt);
> +		if (err)
> +			goto out_free_dev;

You just raced with userspace and lost.  Please properly use a device
group instead.  That makes for smaller code, and it works properly.

thanks,

greg k-h