linux-kernel - Re: [PATCH v9 4/5] documentation: media: add documentation for Toshiba Visconti Video Input Interface driver

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Message-ID: <ZbyQgkGicrnP-XZL@valkosipuli.retiisi.eu>
Date: Fri, 2 Feb 2024 06:49:38 +0000
From: Sakari Ailus <sakari.ailus@....fi>
To: yuji2.ishikawa@...hiba.co.jp
Cc: hverkuil@...all.nl, laurent.pinchart@...asonboard.com,
	mchehab@...nel.org, robh+dt@...nel.org,
	krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
	nobuhiro1.iwamatsu@...hiba.co.jp, linux-media@...r.kernel.org,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 4/5] documentation: media: add documentation for
 Toshiba Visconti Video Input Interface driver

Hi Yuji,

On Mon, Dec 04, 2023 at 04:32:40AM +0000, yuji2.ishikawa@...hiba.co.jp wrote:
> > > +Vendor specific v4l2 controls
> > > +=============================
> > > +
> > > +.. _V4L2_CID_VISCONTI_VIIF_MAIN_SET_RAWPACK_MODE:
> > > +
> > > +V4L2_CID_VISCONTI_VIIF_MAIN_SET_RAWPACK_MODE
> > > +--------------------------------------------
> > > +
> > > +This control sets the format to pack multiple RAW pixel values into a word.
> > > +
> > > +This control accepts a __u32 value defined as `enum viif_rawpack_mode`.
> > > +
> > > +This control should be set before ioctl(S_FMT) and should not be changed
> > after that.
> > 
> > Why do you need this? Doesn't the V4L2 pixelformat already explicitly define
> > the format, including packing?
> > 
> 
> This control value affects the unpacker between CSI2 receiver and ISP.
> The rawpack mode is an option to receive from Wide-Dynamic-Range image
> sensors, whose output bit width is larger than standard format (RAW20,
> RAW24). For example, some WDR image sensors split 20 bit value into
> upper/lower 10bit values, then put them into consective pixels to make a
> double-width RAW10 format image.

Do you have a sensor that really does this? Which one is it?

> 
> This option is only related to the interpretation of CSI2 input data.
> Therefore, I think V4L2 pixel format (for resulting image) is not related
> to it. The media bus format seems more relevant, but there is no
> corresponding definition to this case.

-- 
Regards,

Sakari Ailus