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) -- 1.7.3.4 -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
