linux-kernel - Re: [PATCH v2] media: rcar-vin: Add support to select data pins for YCbCr422-8bit input

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Date:   Mon, 3 Aug 2020 21:15:11 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Niklas <niklas.soderlund@...natech.se>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Biju Das <biju.das.jz@...renesas.com>,
        Prabhakar <prabhakar.csengg@...il.com>
Subject: Re: [PATCH v2] media: rcar-vin: Add support to select data pins for
 YCbCr422-8bit input

Hi Niklas,

On Mon, Aug 3, 2020 at 8:06 PM Niklas <niklas.soderlund@...natech.se> wrote:
> On 2020-08-03 17:02:53 +0100, Lad Prabhakar wrote:
> > Select the data pins for YCbCr422-8bit input format depending on
> > bus_width and data_shift passed as part of DT.
> >
> > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > Reviewed-by: Biju Das <biju.das.jz@...renesas.com>

> > --- a/drivers/media/platform/rcar-vin/rcar-core.c
> > +++ b/drivers/media/platform/rcar-vin/rcar-core.c
> > @@ -624,6 +624,11 @@ static int rvin_parallel_parse_v4l2(struct device *dev,
> >       vin->parallel = rvpe;
> >       vin->parallel->mbus_type = vep->bus_type;
> >
> > +     /* select VInDATA[15:8] pins for YCbCr422-8bit format */
> > +     if (vep->bus.parallel.bus_width == BUS_WIDTH_8 &&
> > +         vep->bus.parallel.data_shift == DATA_SHIFT_8)
> > +             vin->parallel->ycbcr_8b_g = true;
> > +
>
> I would store the bus_width and bus_shift values in the struct
> rvin_parallel_entity and evaluate them in place rater then create a flag
> for this specific use-case..
>
> Also according to the documentation is the check correct? Do we not wish
> to use the new mode when bus_width == 16 and bus_shift == 8. The check
> you have here seems to describe a 8 lane bus where 0 lanes are used.

The bus width used is 8.

Documentation/devicetree/bindings/media/video-interfaces.txt:

  - bus-width: number of data lines actively used, valid for the
parallel busses.
  - data-shift: on the parallel data busses, if bus-width is used to specify the
    number of data lines, data-shift can be used to specify which data lines are
    used, e.g. "bus-width=<8>; data-shift=<2>;" means, that lines 9:2 are used.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds