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Date:   Mon, 6 Nov 2023 16:49:48 +0100
From:   Mehdi Djait <mehdi.djait@bootlin.com>
To:     Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Cc:     mchehab@kernel.org, hverkuil-cisco@xs4all.nl,
        krzysztof.kozlowski+dt@linaro.org, robh+dt@kernel.org,
        conor+dt@kernel.org, laurent.pinchart@ideasonboard.com,
        linux-media@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, thomas.petazzoni@bootlin.com,
        alexandre.belloni@bootlin.com, maxime.chevallier@bootlin.com
Subject: Re: [PATCH v7 3/3] media: i2c: Introduce a driver for the Techwell
 TW9900 decoder
Message-ID: <ZUkLHDH2Budi+zgc@pc-70.home>
References: <cover.1697463708.git.mehdi.djait@bootlin.com>
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 <ZUNz_h1fn9RH9Uc5@aptenodytes>
 <ZUj/FQTyajQJrxoU@pc-70.home>
 <ZUkFXl7vBS36y4Qi@aptenodytes>
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Hi Paul,

On Mon, Nov 06, 2023 at 04:25:18PM +0100, Paul Kocialkowski wrote:
> > > > +static void tw9900_fill_fmt(const struct tw9900_mode *mode,
> > > > +			    struct v4l2_mbus_framefmt *fmt)
> > > > +{
> > > > +	fmt->code = MEDIA_BUS_FMT_UYVY8_2X8;
> > > > +	fmt->width = mode->width;
> > > > +	fmt->height = mode->height;
> > > > +	fmt->field = V4L2_FIELD_NONE;
> > > > +	fmt->quantization = V4L2_QUANTIZATION_DEFAULT;
> > > > +	fmt->colorspace = V4L2_COLORSPACE_SMPTE170M;
> > > > +	fmt->xfer_func = V4L2_MAP_XFER_FUNC_DEFAULT(V4L2_COLORSPACE_SMPTE170M);
> > > > +	fmt->ycbcr_enc = V4L2_MAP_YCBCR_ENC_DEFAULT(V4L2_COLORSPACE_SMPTE170M);
> > > > +}
> > > > +
> > > > +static int tw9900_cfg_fmt(struct v4l2_subdev *sd,
> > > 
> > > You might have to differentiate between set_fmt/get_fmt to return -EBUSY
> > > if streaming is on in set_fmt. However I understand it will just copy the
> > > current mode in both cases, but this might still be required to follow v4l2
> > > semantics (please double-check).
> > > 
> > 
> > This should be done in the driver calling the pad subdev_call set_fmt,
> > right ?
> 
> Well the two things are distinct, even though it's not obvious to think about
> a case where you wouldn't have a video device to grab the frames.
> 
> For instance you can see this being done here:
> https://elixir.bootlin.com/linux/latest/source/drivers/media/i2c/ov5648.c#L2259
> 
> I'm just not sure about what the V4L2 subdev API mandates. It would be useful
> to find some piece of documentation that clarifies the requirement.

Ok, I will split the functions then.

--
Kind Regards
Mehdi Djait