[PATCH v4 3/3] Bluetooth: Add ABI doc for sysfs isoc_alt

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

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

The functionality was completed in commit c04f2e4f4ea1 ("Bluetooth: Fix
possible race with userspace of sysfs isoc_alt")

Fixes: c04f2e4f4ea1 ("Bluetooth: Fix possible race with userspace of sysfs isoc_alt")
Signed-off-by: Hsin-chen Chuang <chharry@chromium.org>
---

(no changes since v1)

 Documentation/ABI/stable/sysfs-class-bluetooth | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/Documentation/ABI/stable/sysfs-class-bluetooth b/Documentation/ABI/stable/sysfs-class-bluetooth
index 36be02471174..c1024c7c4634 100644
--- a/Documentation/ABI/stable/sysfs-class-bluetooth
+++ b/Documentation/ABI/stable/sysfs-class-bluetooth
@@ -7,3 +7,16 @@ Description: 	This write-only attribute allows users to trigger the vendor reset
 		The reset may or may not be done through the device transport
 		(e.g., UART/USB), and can also be done through an out-of-band
 		approach such as GPIO.
+
+What:		/sys/class/bluetooth/btusb<usb-intf>/isoc_alt
+Date:		13-Feb-2025
+KernelVersion:	6.13
+Contact:	linux-bluetooth@vger.kernel.org
+Description:	This attribute allows users to configure the USB Alternate setting
+		for the specific HCI device. Reading this attribute returns the
+		current setting, and writing any supported numbers would change
+		the setting. See the USB Alternate setting definition in Bluetooth
+		core spec 5, vol 4, part B, table 2.1.
+		If the HCI device is not yet init-ed, the write fails with -ENODEV.
+		If the data is not a valid number, the write fails with -EINVAL.
+		The other failures are vendor specific.
-- 
2.48.1.502.g6dc24dfdaf-goog