From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from out5-smtp.messagingengine.com ([66.111.4.29]:40660 "EHLO out5-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751865AbaCYXC6 (ORCPT ); Tue, 25 Mar 2014 19:02:58 -0400 Message-ID: <533209A1.5090806@williammanley.net> Date: Tue, 25 Mar 2014 22:56:33 +0000 From: William Manley MIME-Version: 1.0 To: laurent.pinchart@ideasonboard.com CC: linux-media@vger.kernel.org Subject: Re: [PATCH v2] uvcvideo: Work around buggy Logitech C920 firmware References: <1394647711-25291-1-git-send-email-will@williammanley.net> <1394714328-29969-1-git-send-email-will@williammanley.net> In-Reply-To: <1394714328-29969-1-git-send-email-will@williammanley.net> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: On 13/03/14 12:38, William Manley wrote: > The uvcvideo webcam driver exposes the v4l2 control "Exposure (Absolute)" > which allows the user to control the exposure time of the webcam, > essentially controlling the brightness of the received image. By default > the webcam automatically adjusts the exposure time automatically but the > if you set the control "Exposure, Auto"="Manual Mode" the user can fix > the exposure time. > > Unfortunately it seems that the Logitech C920 has a firmware bug where > it will forget that it's in manual mode temporarily during initialisation. > This means that the camera doesn't respect the exposure time that the user > requested if they request it before starting to stream video. They end up > with a video stream which is either too bright or too dark and must reset > the controls after video starts streaming. > > This patch introduces the quirk UVC_QUIRK_RESTORE_CTRLS_ON_INIT which > causes the cached controls to be re-uploaded to the camera immediately > after initialising the camera. This quirk is applied to the C920 to work > around this camera bug. > > Changes since patch v1: > * Introduce quirk so workaround is only applied to the C920. > > Signed-off-by: William Manley Bump?