media: uvcvideo: Fix comments in uvc_meta_detect_msxu

The comments can be more precise. Let's fix them.

Fixes: 6cb786f ("media: uvcvideo: Auto-set UVC_QUIRK_MSXU_META")
Cc: stable+noautosel@kernel.org # Coment change only, no need to backport
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Hans de Goede <hansg@kernel.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

Author: ribalda

drivers/media/usb/uvc/uvc_metadata.c

@@ -196,7 +196,10 @@ static int uvc_meta_detect_msxu(struct uvc_device *dev)
 	if (!data)
 		return -ENOMEM;
 
-	/* Check if the metadata is already enabled. */
+	/*
+	 * Check if the metadata is already enabled, or if the device always
+	 * returns metadata.
+	 */
 	ret = uvc_query_ctrl(dev, UVC_GET_CUR, entity->id, dev->intfnum,
 			     MSXU_CONTROL_METADATA, data, sizeof(*data));
 	if (ret)
@@ -208,9 +211,11 @@ static int uvc_meta_detect_msxu(struct uvc_device *dev)
 	}
 
 	/*
-	 * We have seen devices that require 1 to enable the metadata, others
-	 * requiring a value != 1 and others requiring a value >1. Luckily for
-	 * us, the value from GET_MAX seems to work all the time.
+	 * Set the value of MSXU_CONTROL_METADATA to the value reported by
+	 * GET_MAX to enable production of MSXU metadata. The GET_MAX request
+	 * reports the maximum size of the metadata, if its value is 0 then MSXU
+	 * metadata is not supported. For more information, see
+	 * https://learn.microsoft.com/en-us/windows-hardware/drivers/stream/uvc-extensions-1-5#2229-metadata-control
 	 */
 	ret = uvc_query_ctrl(dev, UVC_GET_MAX, entity->id, dev->intfnum,
 			     MSXU_CONTROL_METADATA, data, sizeof(*data));