From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from aer-iport-1.cisco.com ([173.38.203.51]:34484 "EHLO aer-iport-1.cisco.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752938AbbD2IE5 (ORCPT ); Wed, 29 Apr 2015 04:04:57 -0400 Message-ID: <55408DE7.3020906@cisco.com> Date: Wed, 29 Apr 2015 09:53:11 +0200 From: Hans Verkuil MIME-Version: 1.0 To: Jacek Anaszewski , linux-media CC: Ricardo Ribalda Delgado , Hans Verkuil , Sakari Ailus Subject: Re: S_CTRL must be called twice to set volatile controls References: <5540895A.5060102@samsung.com> In-Reply-To: <5540895A.5060102@samsung.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: Hi Jacek, On 04/29/15 09:33, Jacek Anaszewski wrote: > Hi, > > After testing my v4l2-flash helpers patch [1] with the recent patches > for v4l2-ctrl.c ([2] and [3]) s_ctrl op isn't called despite setting > the value that should be aligned to the other step than default one. > > This happens for V4L2_CID_FLASH_TORCH_INTENSITY control with > V4L2_CTRL_FLAG_VOLATILE flag. > > The situation improves after setting V4L2_CTRL_FLAG_EXECUTE_ON_WRITE > flag for the control. Is this flag required now for volatile controls > to be writable? Yes, you need that if you want to be able to write to a volatile control. It was added for exactly that purpose. Why is V4L2_CID_FLASH_TORCH_INTENSITY volatile? Volatile typically only makes sense if the hardware itself is modifying the value without the software knowing about it. Regards, Hans > > [1] http://www.spinics.net/lists/linux-media/msg89004.html > [2] 45f014c5 [media] media/v4l2-ctrls: Always execute EXECUTE_ON_WRITE ctrls > [3] b08d8d26 [media] media/v4l2-ctrls: volatiles should not generate CH_VALUE