Re: [PATCH] uvcvideo: Fix V4L2 button controls that share the same UVC control

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looks good, ack.

Acked-by: Hans de Goede <hdegoede@xxxxxxxxxx>

On 05/11/2012 03:55 PM, Laurent Pinchart wrote:
The Logitech pan/tilt reset UVC control contains two V4L2 button
controls to reset pan and tilt. As the UVC control is not marked as
auto-update, the button bits are set but never reset. A pan reset that
follows a tilt reset would thus reset both pan and tilt.

Fix this by not caching the control value of write-only controls. All
standard UVC controls are either readable or auto-update, so this will
not cause any regression and will not result in extra USB requests.

Reported-by: Hans de Goede<hdegoede@xxxxxxxxxx>
Signed-off-by: Laurent Pinchart<laurent.pinchart@xxxxxxxxxxxxxxxx>
---
  drivers/media/video/uvc/uvc_ctrl.c |    7 +++++--
  1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/media/video/uvc/uvc_ctrl.c b/drivers/media/video/uvc/uvc_ctrl.c
index 28363b7..3bc119b 100644
--- a/drivers/media/video/uvc/uvc_ctrl.c
+++ b/drivers/media/video/uvc/uvc_ctrl.c
@@ -1348,9 +1348,12 @@ static int uvc_ctrl_commit_entity(struct uvc_device *dev,

  		/* Reset the loaded flag for auto-update controls that were
  		 * marked as loaded in uvc_ctrl_get/uvc_ctrl_set to prevent
-		 * uvc_ctrl_get from using the cached value.
+		 * uvc_ctrl_get from using the cached value, and for write-only
+		 * controls to prevent uvc_ctrl_set from setting bits not
+		 * explicitly set by the user.
  		 */
-		if (ctrl->info.flags&  UVC_CTRL_FLAG_AUTO_UPDATE)
+		if (ctrl->info.flags&  UVC_CTRL_FLAG_AUTO_UPDATE ||
+		    !(ctrl->info.flags&  UVC_CTRL_FLAG_GET_CUR))
  			ctrl->loaded = 0;

  		if (!ctrl->dirty)
--
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