linux-kernel - Re: [PATCH v2 0/7] [PATCH v2 0/7] Add support of OV9655 camera

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Date:   Wed, 12 Jul 2017 22:01:59 +0200
From:   Sylwester Nawrocki <snawrocki@...nel.org>
To:     Hugues Fruchet <hugues.fruchet@...com>
Cc:     "H. Nikolaus Schaller" <hns@...delico.com>,
        Guennadi Liakhovetski <g.liakhovetski@....de>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hverkuil@...all.nl>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Yannick Fertre <yannick.fertre@...com>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org
Subject: Re: [PATCH v2 0/7] [PATCH v2 0/7] Add support of OV9655 camera

Hi Hugues,

On 07/03/2017 11:16 AM, Hugues Fruchet wrote:
> This patchset enables OV9655 camera support.
> 
> OV9655 support has been tested using STM32F4DIS-CAM extension board
> plugged on connector P1 of STM32F746G-DISCO board.
> Due to lack of OV9650/52 hardware support, the modified related code
> could not have been checked for non-regression.
> 
> First patches upgrade current support of OV9650/52 to prepare then
> introduction of OV9655 variant patch.
> Because of OV9655 register set slightly different from OV9650/9652,
> not all of the driver features are supported (controls). Supported
> resolutions are limited to VGA, QVGA, QQVGA.
> Supported format is limited to RGB565.
> Controls are limited to color bar test pattern for test purpose.

I appreciate your efforts towards making a common driver but IMO it would be 
better to create a separate driver for the OV9655 sensor.  The original driver 
is 1576 lines of code, your patch set adds half of that (816).  There are
significant differences in the feature set of both sensors, there are 
differences in the register layout.  I would go for a separate driver, we  
would then have code easier to follow and wouldn't need to worry about possible
regressions.  I'm afraid I have lost the camera module and won't be able 
to test the patch set against regressions.

IMHO from maintenance POV it's better to make a separate driver. In the end 
of the day we wouldn't be adding much more code than it is being done now.

>   .../devicetree/bindings/media/i2c/ov965x.txt       |  45 ++
>   drivers/media/i2c/Kconfig                          |   6 +-
>   drivers/media/i2c/ov9650.c                         | 816 +++++++++++++++++----
>   3 files changed, 736 insertions(+), 131 deletions(-)
>   create mode 100644 Documentation/devicetree/bindings/media/i2c/ov965x.txt

--
Thanks,
Sylwester