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From: Tomasz Figa <tfiga@chromium.org>
Date: Thu, 10 May 2018 09:15:31 +0000
Message-ID: <CAAFQd5CEdwJ485RQEQ=aZRYtCO-HPE0NgudXKRjVDSbwpbiC5w@mail.gmail.com>
Subject: Re: [PATCH v11] media: imx258: Add imx258 camera sensor driver
To: "Zheng, Jian Xu" <jian.xu.zheng@intel.com>
Cc: "Chen, JasonX Z" <jasonx.z.chen@intel.com>,
        "Yeh, Andy" <andy.yeh@intel.com>,
        Linux Media Mailing List <linux-media@vger.kernel.org>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        Alan Chiang <alanx.chiang@intel.com>
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On Thu, May 10, 2018 at 6:11 PM Zheng, Jian Xu <jian.xu.zheng@intel.com>
wrote:

> Hi Tomasz,

> > -----Original Message-----
> > From: linux-media-owner@vger.kernel.org [mailto:linux-media-
> > owner@vger.kernel.org] On Behalf Of Tomasz Figa
> > Sent: Thursday, May 10, 2018 3:04 PM
> > To: Zheng, Jian Xu <jian.xu.zheng@intel.com>
> > Cc: Chen, JasonX Z <jasonx.z.chen@intel.com>; Yeh, Andy
> > <andy.yeh@intel.com>; Linux Media Mailing List <linux-
> > media@vger.kernel.org>; Sakari Ailus <sakari.ailus@linux.intel.com>;
Chiang,
> > AlanX <alanx.chiang@intel.com>
> > Subject: Re: [PATCH v11] media: imx258: Add imx258 camera sensor driver
> >
> > On Thu, May 10, 2018 at 3:56 PM Zheng, Jian Xu <jian.xu.zheng@intel.com>
> > wrote:
> >
> > > Hi Tomasz,
> >
> > > > -----Original Message-----
> > > > From: linux-media-owner@vger.kernel.org [mailto:linux-media-
> > > > owner@vger.kernel.org] On Behalf Of Tomasz Figa
> > > > Sent: Wednesday, May 9, 2018 6:05 PM
> > > > To: Chen, JasonX Z <jasonx.z.chen@intel.com>
> > > > Cc: Yeh, Andy <andy.yeh@intel.com>; Linux Media Mailing List <linux-
> > > > media@vger.kernel.org>; Sakari Ailus <sakari.ailus@linux.intel.com>;
> > Chiang,
> > > > AlanX <alanx.chiang@intel.com>
> > > > Subject: Re: [PATCH v11] media: imx258: Add imx258 camera sensor
> > > > driver
> > > >
> > > > Hi Jason,
> > > >
> > > > > IPU3 HAL has a handler to bind test_pattern mode.
> > > > > The COLOR BAR MODE in HAL has been configured to 1 when APP
> > > > > requests to
> > > > output color bar image.
> > > > > However Sony sensor's COLOR BAR MODE is designed as 2 in register
> > table.
> > > > (grey color bars as 1).
> > > > > When HAL sends handler to driver to switch test pattern mode (to
> > > > > COLOR
> > > > BAR - val: 1), it will be grey color, since driver still set
> > TEST_PATTERN_MODE
> > > > reg value to 1, those it is not what we expected.
> > > >
> > > > > That is why we have to make an array with index to arrange the
> > > > > order of
> > > > the test pattern items, so driver will choose COLOR BAR correctly
> > > > when
> > HAL
> > > > send test_pattern message (with 1).
> > > > > The concept is the test_pattern_menu could be listed in driver per
> > > > > real
> > > > requirement, no matter how the sensor register is designed.
> > > >
> > > >
> > > > V4L2 specification does not define any particular order of menu
> > > > entries
> > in
> > > > V4L2_CID_TEST_PATTERN. The application should query the strings in
> > > > the menu and determine the option it needs based on that. If it
> > > > hardcodes particular index, it's a bug.
> >
> > > Is there any reason that there is no certain macro define for
> > > different
> > type of test pattern in v4l2?
> > > So App will not depend on any strings where could be different on
> > different sensor drivers.
> >
> > Yes. Available patterns differ significantly between one sensor and
another,
> > so the menu positions are considered hardware-specific.

> The problem is even App queries the strings in driver, it still doesn't
look good enough.
> Because different driver may have different strings even for same type,
Color Bar, for example.
> So it's the best v4l2 could have several standardize names for test
pattern types.
> In this case App doesn't need to hard code test pattern strings for
different sensors.

> Do you think it makes sense?

It sounds quite sensible, assuming that we can find such standard subset.

IMHO a much more scale-able solution would be to have the test pattern
strings configurable per platform.

Best regards,
Tomasz