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Message-Id: <201212111005.59210.hverkuil@xs4all.nl> Date: Tue, 11 Dec 2012 10:05:59 +0100 From: Hans Verkuil <hverkuil@...all.nl> To: Sakari Ailus <sakari.ailus@....fi> Cc: Prabhakar Lad <prabhakar.csengg@...il.com>, LMML <linux-media@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, LDOC <linux-doc@...r.kernel.org>, Laurent Pinchart <laurent.pinchart@...asonboard.com>, Kyungmin Park <kyungmin.park@...sung.com>, Guennadi Liakhovetski <g.liakhovetski@....de>, Sylwester Nawrocki <s.nawrocki@...sung.com>, Hans Verkuil <hans.verkuil@...co.com>, Hans de Goede <hdegoede@...hat.com>, Chris MacGregor <chris@...ermato.com>, Rob Landley <rob@...dley.net>, Jeongtae Park <jtp.park@...sung.com>, Mauro Carvalho Chehab <mchehab@...radead.org> Subject: Re: [PATCH RFC v2] media: v4l2-ctrl: Add gain controls On Tue 11 December 2012 09:56:42 Hans Verkuil wrote: > 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 <hverkuil@...all.nl> wrote: > > > > (resend without HTML formatting) > > > > > > > > On Wed 5 December 2012 12:49:29 Prabhakar Lad wrote: > > > >> From: Lad, Prabhakar <prabhakar.csengg@...il.com> > > > >> > > > >> add support for per color component digital/analog gain controls > > > >> and also their corresponding offset. > > > > > > > > Some obvious questions below... > > > > > > > >> > > > >> Signed-off-by: Lad, Prabhakar <prabhakar.csengg@...il.com> > > > >> Cc: Sakari Ailus <sakari.ailus@....fi> > > > >> Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com> > > > >> Cc: Kyungmin Park <kyungmin.park@...sung.com> > > > >> Cc: Guennadi Liakhovetski <g.liakhovetski@....de> > > > >> Cc: Sylwester Nawrocki <s.nawrocki@...sung.com> > > > >> Cc: Hans Verkuil <hans.verkuil@...co.com> > > > >> Cc: Hans de Goede <hdegoede@...hat.com> > > > >> Cc: Chris MacGregor <chris@...ermato.com> > > > >> Cc: Rob Landley <rob@...dley.net> > > > >> Cc: Jeongtae Park <jtp.park@...sung.com> > > > >> Cc: Mauro Carvalho Chehab <mchehab@...radead.org> > > > >> --- > > > >> 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.</para> > > > >> specific test patterns can be used to test if a device is working > > > >> properly.</entry> > > > >> </row> > > > >> + <row> > > > >> + <entry spanname="id"><constant>V4L2_CID_GAIN_RED</constant></entry> > > > >> + <entry>integer</entry> > > > >> + </row> > > > >> + <row> > > > >> + <entry spanname="id"><constant>V4L2_CID_GAIN_GREEN_RED</constant></entry> > > > >> + <entry>integer</entry> > > > >> + </row> > > > >> + <row> > > > >> + <entry spanname="id"><constant>V4L2_CID_GAIN_GREEN_BLUE</constant></entry> > > > >> + <entry>integer</entry> > > > >> + </row> > > > >> + <row> > > > >> + <entry spanname="id"><constant>V4L2_CID_GAIN_BLUE</constant></entry> > > > >> + <entry>integer</entry> > > > >> + </row> > > > >> + <row> > > > >> + <entry spanname="id"><constant>V4L2_CID_GAIN_GREEN</constant></entry> > > > >> + <entry>integer</entry> > > > >> + </row> > > > >> + <row> > > > >> + <entry spanname="descr"> Some capture/sensor devices have > > > >> + the capability to set per color component digital/analog gain values.</entry> > > > >> + </row> > > > >> + <row> > > > >> + <entry spanname="id"><constant>V4L2_CID_GAIN_OFFSET</constant></entry> > > > >> + <entry>integer</entry> > > > >> + </row> > > > >> + <row> > > > >> + <entry spanname="id"><constant>V4L2_CID_BLUE_OFFSET</constant></entry> > > > >> + <entry>integer</entry> > > > >> + </row> > > > >> + <row> > > > >> + <entry spanname="id"><constant>V4L2_CID_RED_OFFSET</constant></entry> > > > >> + <entry>integer</entry> > > > >> + </row> > > > >> + <row> > > > >> + <entry spanname="id"><constant>V4L2_CID_GREEN_OFFSET</constant></entry> > > > >> + <entry>integer</entry> > > > >> + </row> > > > >> + <row> > > > >> + <entry spanname="id"><constant>V4L2_CID_GREEN_RED_OFFSET</constant></entry> > > > >> + <entry>integer</entry> > > > >> + </row> > > > >> + <row> > > > >> + <entry spanname="id"><constant>V4L2_CID_GREEN_BLUE_OFFSET</constant></entry> > > > >> + <entry>integer</entry> > > > >> + </row> > > > >> + <row> > > > >> + <entry spanname="descr"> 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.</entry> > > > > > > > > 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? I guess GAIN_RED + GAIN_RED_OFFSET is fine as a combination after reading up on it a bit. It's the global vs per-component that's the problem. After thinking about it some more I'd say it should be either one or the other, with a possible control to switch between the two if both modes are supported. It gets very messy otherwise. Regards, Hans > > > 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 > -- > To unsubscribe from this list: send the line "unsubscribe linux-media" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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