From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752567Ab2LKI5T (ORCPT ); Tue, 11 Dec 2012 03:57:19 -0500 Received: from ams-iport-4.cisco.com ([144.254.224.147]:61572 "EHLO ams-iport-4.cisco.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751625Ab2LKI5S convert rfc822-to-8bit (ORCPT ); Tue, 11 Dec 2012 03:57:18 -0500 X-IronPort-AV: E=McAfee;i="5400,1158,6922"; a="10326589" From: Hans Verkuil To: Sakari Ailus Subject: Re: [PATCH RFC v2] media: v4l2-ctrl: Add gain controls Date: Tue, 11 Dec 2012 09:56:42 +0100 User-Agent: KMail/1.13.7 (Linux/3.6-7.slh.1-aptosid-amd64; KDE/4.8.4; x86_64; ; ) Cc: Prabhakar Lad , LMML , LKML , LDOC , Laurent Pinchart , Kyungmin Park , Guennadi Liakhovetski , Sylwester Nawrocki , Hans Verkuil , Hans de Goede , Chris MacGregor , Rob Landley , Jeongtae Park , Mauro Carvalho Chehab References: <1354708169-1139-1-git-send-email-prabhakar.csengg@gmail.com> <20121206095431.GA2887@valkosipuli.retiisi.org.uk> In-Reply-To: <20121206095431.GA2887@valkosipuli.retiisi.org.uk> MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 8BIT Message-Id: <201212110956.43081.hverkuil@xs4all.nl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 6 December 2012 10:54:32 Sakari Ailus wrote: > Hi Prabhakar and Hans, > > On Thu, Dec 06, 2012 at 10:24:18AM +0530, Prabhakar Lad wrote: > > Hi Hans, > > > > On Wed, Dec 5, 2012 at 5:38 PM, Hans Verkuil wrote: > > > (resend without HTML formatting) > > > > > > On Wed 5 December 2012 12:49:29 Prabhakar Lad wrote: > > >> From: Lad, Prabhakar > > >> > > >> add support for per color component digital/analog gain controls > > >> and also their corresponding offset. > > > > > > Some obvious questions below... > > > > > >> > > >> Signed-off-by: Lad, Prabhakar > > >> Cc: Sakari Ailus > > >> Cc: Laurent Pinchart > > >> Cc: Kyungmin Park > > >> Cc: Guennadi Liakhovetski > > >> Cc: Sylwester Nawrocki > > >> Cc: Hans Verkuil > > >> Cc: Hans de Goede > > >> Cc: Chris MacGregor > > >> Cc: Rob Landley > > >> Cc: Jeongtae Park > > >> Cc: Mauro Carvalho Chehab > > >> --- > > >> Changes for v2: > > >> 1: Fixed review comments pointed by Laurent. > > >> 2: Rebased on latest tree. > > >> > > >> Documentation/DocBook/media/v4l/controls.xml | 54 ++++++++++++++++++++++++++ > > >> drivers/media/v4l2-core/v4l2-ctrls.c | 11 +++++ > > >> include/uapi/linux/v4l2-controls.h | 11 +++++ > > >> 3 files changed, 76 insertions(+), 0 deletions(-) > > >> > > >> diff --git a/Documentation/DocBook/media/v4l/controls.xml b/Documentation/DocBook/media/v4l/controls.xml > > >> index 7fe5be1..847a9bb 100644 > > >> --- a/Documentation/DocBook/media/v4l/controls.xml > > >> +++ b/Documentation/DocBook/media/v4l/controls.xml > > >> @@ -4543,6 +4543,60 @@ interface and may change in the future. > > >> specific test patterns can be used to test if a device is working > > >> properly. > > >> > > >> + > > >> + V4L2_CID_GAIN_RED > > >> + integer > > >> + > > >> + > > >> + V4L2_CID_GAIN_GREEN_RED > > >> + integer > > >> + > > >> + > > >> + V4L2_CID_GAIN_GREEN_BLUE > > >> + integer > > >> + > > >> + > > >> + V4L2_CID_GAIN_BLUE > > >> + integer > > >> + > > >> + > > >> + V4L2_CID_GAIN_GREEN > > >> + integer > > >> + > > >> + > > >> + Some capture/sensor devices have > > >> + the capability to set per color component digital/analog gain values. > > >> + > > >> + > > >> + V4L2_CID_GAIN_OFFSET > > >> + integer > > >> + > > >> + > > >> + V4L2_CID_BLUE_OFFSET > > >> + integer > > >> + > > >> + > > >> + V4L2_CID_RED_OFFSET > > >> + integer > > >> + > > >> + > > >> + V4L2_CID_GREEN_OFFSET > > >> + integer > > >> + > > >> + > > >> + V4L2_CID_GREEN_RED_OFFSET > > >> + integer > > >> + > > >> + > > >> + V4L2_CID_GREEN_BLUE_OFFSET > > >> + integer > > >> + > > >> + > > >> + Some capture/sensor devices have the > > >> + capability to set per color component digital/analog gain offset values. > > >> + V4L2_CID_GAIN_OFFSET is the global gain offset and the rest are per > > >> + color component gain offsets. > > > > > > If I set both V4L2_CID_GAIN_RED and V4L2_CID_RED_OFFSET, how are they supposed > > > to interact? Or are they mutually exclusive? > > > > > > And if I set both V4L2_CID_GAIN_OFFSET and V4L2_CID_RED_OFFSET, how are they supposed > > > to interact? > > > > > > This questions should be answered in the documentation... > > > > > I haven’t worked on the hardware which supports both, What is the general > > behaviour when the hardware supports both per color component and global > > and both of them are set ? That could be helpful for me to document. > > I'd guess most of the time only either one is supported, Are you talking about GAIN_RED vs GAIN_RED_OFFSET or GAIN_OFFSET vs RED_OFFSET? Or both? > and when someone > thinks of supporting both on the same device, we can start thinking of the > interaction of per-component and global ones. That may be hardware specific > as well, so standardising it might not be possible. > > I think it'd be far more important to know which unit is it. Many such > controls are indeed fixed point values but the location of the point varies. > For unstance, u16,u16 and u8,u8 aren't uncommon. We currently have no way to > tell this to the user space. This isn't in any way specific to gain or > offset controls, though. There are no standardized units for gain at the moment, and I don't really see that happening any time soon. Fixed point isn't supported at all as a control type, so that will have to be converted to an integer anyway. Prabhakar, which of these controls are actually supported by your hardware? Regards, Hans