Date:	Sun, 9 Sep 2012 10:40:17 +0300
From:	Sakari Ailus <sakari.ailus@....fi>
To:	Hans Verkuil <hverkuil@...all.nl>
Cc:	Prabhakar Lad <prabhakar.lad@...com>,
	LMML <linux-media@...r.kernel.org>,
	dlos <davinci-linux-open-source@...ux.davincidsp.com>,
	linux-kernel@...r.kernel.org,
	Manjunath Hadli <manjunath.hadli@...com>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	linux-doc@...r.kernel.org, Hans Verkuil <hans.verkuil@...co.com>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Mauro Carvalho Chehab <mchehab@...radead.org>,
	Hans de Goede <hdegoede@...hat.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Rob Landley <rob@...dley.net>
Subject: Re: [PATCH v2] media: v4l2-ctrls: add control for test pattern

Hi Hans,

On Sat, Sep 08, 2012 at 01:11:04PM +0200, Hans Verkuil wrote:
> On Fri September 7 2012 20:20:51 Sakari Ailus wrote:
> > Hi Prabhakar,
> > 
> > Thanks for the patch!
> > 
> > Prabhakar Lad wrote:
> > > From: Lad, Prabhakar <prabhakar.lad@...com>
> > >
> > > add V4L2_CID_TEST_PATTERN of type menu, which determines
> > > the internal test pattern selected by the device.
> > >
> > > Signed-off-by: Lad, Prabhakar <prabhakar.lad@...com>
> > > Signed-off-by: Manjunath Hadli <manjunath.hadli@...com>
> > > Cc: Sakari Ailus <sakari.ailus@....fi>
> > > Cc: Hans Verkuil <hans.verkuil@...co.com>
> > > Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> > > Cc: Mauro Carvalho Chehab <mchehab@...radead.org>
> > > Cc: Sylwester Nawrocki <s.nawrocki@...sung.com>
> > > Cc: Hans de Goede <hdegoede@...hat.com>
> > > Cc: Kyungmin Park <kyungmin.park@...sung.com>
> > > Cc: Rob Landley <rob@...dley.net>
> > > ---
> > > This patches has one checkpatch warning for line over
> > > 80 characters altough it can be avoided I have kept it
> > > for consistency.
> > >
> > > Changes for v2:
> > > 1: Included display devices in the description for test pattern
> > >     as pointed by Hans.
> > > 2: In the menu replaced 'Test Pattern Disabled' by 'Disabled' as
> > >     pointed by Sylwester.
> > > 3: Removed the test patterns from menu as the are hardware specific
> > >     as pointed by Sakari.
> > >
> > >   Documentation/DocBook/media/v4l/controls.xml |   20 ++++++++++++++++++++
> > >   drivers/media/v4l2-core/v4l2-ctrls.c         |    8 ++++++++
> > >   include/linux/videodev2.h                    |    4 ++++
> > >   3 files changed, 32 insertions(+), 0 deletions(-)
> > >
> > > diff --git a/Documentation/DocBook/media/v4l/controls.xml b/Documentation/DocBook/media/v4l/controls.xml
> > > index ad873ea..173934e 100644
> > > --- a/Documentation/DocBook/media/v4l/controls.xml
> > > +++ b/Documentation/DocBook/media/v4l/controls.xml
> > > @@ -4311,6 +4311,26 @@ interface and may change in the future.</para>
> > >   	      </tbody>
> > >   	    </entrytbl>
> > >   	  </row>
> > > +	  <row>
> > > +	    <entry spanname="id"><constant>V4L2_CID_TEST_PATTERN</constant></entry>
> > > +	    <entry>menu</entry>
> > > +	  </row>
> > > +	  <row id="v4l2-test-pattern">
> > > +	    <entry spanname="descr"> The Capture/Display/Sensors have the capability
> > > +	    to generate internal test patterns and this are hardware specific. This
> > > +	    test patterns are used to test a device is properly working and can generate
> > > +	    the desired waveforms that it supports.</entry>
> > > +	  </row>
> > > +	  <row>
> > > +	    <entrytbl spanname="descr" cols="2">
> > > +	      <tbody valign="top">
> > > +	        <row>
> > > +	         <entry><constant>V4L2_TEST_PATTERN_DISABLED</constant></entry>
> > > +	          <entry>Test pattern generation is disabled</entry>
> > > +	        </row>
> > > +	      </tbody>
> > > +	    </entrytbl>
> > > +	  </row>
> > >   	<row><entry></entry></row>
> > >   	</tbody>
> > >         </tgroup>
> > > diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
> > > index 8f2f40b..d731422 100644
> > > --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> > > +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> > > @@ -430,6 +430,10 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
> > >   		"Advanced",
> > >   		NULL,
> > >   	};
> > > +	static const char * const test_pattern[] = {
> > > +		"Disabled",
> > > +		NULL,
> > > +	};
> > >
> > >   	switch (id) {
> > >   	case V4L2_CID_MPEG_AUDIO_SAMPLING_FREQ:
> > > @@ -509,6 +513,8 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
> > >   		return jpeg_chroma_subsampling;
> > >   	case V4L2_CID_DPCM_PREDICTOR:
> > >   		return dpcm_predictor;
> > > +	case V4L2_CID_TEST_PATTERN:
> > > +		return test_pattern;
> > 
> > I think it's not necessary to define test_pattern (nor be prepared to 
> > return it) since the menu is going to be device specific. So the driver 
> > is responsible for all of the menu items. Such menus are created using 
> > v4l2_ctrl_new_custom() instead of v4l2_ctrl_new_std_menu().
> > 
> > Looks good to me otherwise.
> 
> I would suggest that we *do* make this a standard control, but the menu consists
> of just one item: "Disabled". After creating the control you can just set the
> ctrl->qmenu pointer to the device-specific menu. I like using standard controls
> because they guarantee standard naming and type conventions. They are also
> easier to use in an application.

That's not quite enough. Also menu_skip_mask and max also need to be
replaced. In a general case min as well. It's easy to do mistakes in that
--- how about a separate function for doing that? It'd be also nice to be
able to use the existing standardised menu item strings, but that's just an
extra plus.

However I think it's beyond this patch, which I think then is be fine w/o
modifications. So on my behalf,

Acked-by: Sakari Ailus <sakari.ailus@....fi>

Cheers,

-- 
Sakari Ailus
e-mail: sakari.ailus@....fi	XMPP: sailus@...iisi.org.uk
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