Re: [PATCH v2 7/7] drm: rcar-du: Add new formats (2-10-10-10 ARGB, Y210)

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Hans,

On Tue, Dec 20, 2022 at 10:01 AM Hans Verkuil <hverkuil-cisco@xs4all.nl> wrote:
> On 19/12/2022 22:47, Laurent Pinchart wrote:
> > (CC'ing Sakari and Hans)
> >
> > Thank you for the patch.
> >
> > On Mon, Dec 19, 2022 at 04:01:39PM +0200, Tomi Valkeinen wrote:
> >> Add new pixel formats: RGBX1010102, RGBA1010102, ARGB2101010 and Y210.
> >>
> >> Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
> >> ---
> >>  drivers/gpu/drm/rcar-du/rcar_du_kms.c | 24 +++++++++++++
> >>  drivers/gpu/drm/rcar-du/rcar_du_vsp.c | 49 +++++++++++++++++++++++++--
> >>  2 files changed, 71 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_kms.c b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> >> index 8c2719efda2a..8ccabf5a30c4 100644
> >> --- a/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> >> +++ b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> >> @@ -259,6 +259,24 @@ static const struct rcar_du_format_info rcar_du_format_infos[] = {
> >>              .bpp = 32,
> >>              .planes = 1,
> >>              .hsub = 1,
> >> +    }, {
> >> +            .fourcc = DRM_FORMAT_RGBX1010102,
> >
> > Ah, here the format makes sense.
> >
> >> +            .v4l2 = V4L2_PIX_FMT_XBGR2101010,
> >
> > But this is horrible :-( Could we use the same names as DRM for new
> > formats, when there is no conflict with existing V4L2 formats ?
> >
> > Sakari, Hans, what do you think ? Please see patch 1/7 in the series for
> > the format definitions.
>
> V4L2 describes pixel formats based on how they appear in memory from the
> lowest to highest memory address.

So that means big endian?

> If I am not mistaken, DRM uses the CPU order. So that explains the difference
> in naming. I don't think we should hide that difference. And V4L2 has been
> quite consistent in following memory ordering in the naming (except possibly
> for some of the really old pixelformats).

DRM uses little endian.

> Departing from that would be more of a hindrance than a help, IMHO.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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