linux-kernel - Re: [PATCH 6/7] drm/sun4i: de2: Don't return de2_fmt

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Date:   Wed, 26 Feb 2020 11:29:48 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Jernej Škrabec <jernej.skrabec@...l.net>
Cc:     Maxime Ripard <maxime@...no.tech>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 6/7] drm/sun4i: de2: Don't return de2_fmt_info struct

On Wed, Feb 26, 2020 at 2:50 AM Jernej Škrabec <jernej.skrabec@...l.net> wrote:
>
> Hi!
>
> Dne torek, 25. februar 2020 ob 09:52:18 CET je Chen-Yu Tsai napisal(a):
> > On Tue, Feb 25, 2020 at 4:35 PM Maxime Ripard <maxime@...no.tech> wrote:
> > > Hi,
> > >
> > > On Mon, Feb 24, 2020 at 06:39:00PM +0100, Jernej Skrabec wrote:
> > > > Now that de2_fmt_info contains only DRM <-> HW format mapping, it
> > > > doesn't make sense to return pointer to structure when searching by DRM
> > > > format. Rework that to return only HW format instead.
> > > >
> > > > This doesn't make any functional change.
> > > >
> > > > Signed-off-by: Jernej Skrabec <jernej.skrabec@...l.net>
> > > > ---
> > > >
> > > >  drivers/gpu/drm/sun4i/sun8i_mixer.c    | 15 +++++++++++----
> > > >  drivers/gpu/drm/sun4i/sun8i_mixer.h    |  7 +------
> > > >  drivers/gpu/drm/sun4i/sun8i_ui_layer.c | 10 +++++-----
> > > >  drivers/gpu/drm/sun4i/sun8i_vi_layer.c | 12 ++++++------
> > > >  4 files changed, 23 insertions(+), 21 deletions(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/sun4i/sun8i_mixer.c
> > > > b/drivers/gpu/drm/sun4i/sun8i_mixer.c index e078ec96de2d..56cc037fd312
> > > > 100644
> > > > --- a/drivers/gpu/drm/sun4i/sun8i_mixer.c
> > > > +++ b/drivers/gpu/drm/sun4i/sun8i_mixer.c
> > > > @@ -27,6 +27,11 @@
> > > >
> > > >  #include "sun8i_vi_layer.h"
> > > >  #include "sunxi_engine.h"
> > > >
> > > > +struct de2_fmt_info {
> > > > +     u32     drm_fmt;
> > > > +     u32     de2_fmt;
> > > > +};
> > > > +
> > > >
> > > >  static const struct de2_fmt_info de2_formats[] = {
> > > >
> > > >       {
> > > >
> > > >               .drm_fmt = DRM_FORMAT_ARGB8888,
> > > >
> > > > @@ -230,15 +235,17 @@ static const struct de2_fmt_info de2_formats[] = {
> > > >
> > > >       },
> > > >
> > > >  };
> > > >
> > > > -const struct de2_fmt_info *sun8i_mixer_format_info(u32 format)
> > > > +int sun8i_mixer_drm_format_to_hw(u32 format, u32 *hw_format)
> > > >
> > > >  {
> > > >
> > > >       unsigned int i;
> > > >
> > > >       for (i = 0; i < ARRAY_SIZE(de2_formats); ++i)
> > > >
> > > > -             if (de2_formats[i].drm_fmt == format)
> > > > -                     return &de2_formats[i];
> > > > +             if (de2_formats[i].drm_fmt == format) {
> > > > +                     *hw_format = de2_formats[i].de2_fmt;
> > > > +                     return 0;
> > > > +             }
> > > >
> > > > -     return NULL;
> > > > +     return -EINVAL;
> > > >
> > > >  }
> > >
> > > I'm not too sure about that one. It breaks the consistency with the
> > > other functions, and I don't really see a particular benefit to it?
> >
>
> I don't have strong opinion about this patch. It can be dropped.
>
> > I guess we could just define an "invalid" value, and have the function
> > return that if can't find a match? I'm guessing 0x0 is valid, so maybe
> > 0xffffffff or 0xdeadbeef ?
> >
> > That would keep consistency with everything else all the while
> > removing the level of indirection you wanted to.
>
> I modeled this after
> static int sun4i_backend_drm_format_to_layer(u32 format, u32 *mode);
> from sun4i_backend.c.
>
> What consistency do you have in mind?

Directly returning values (or error codes) instead of passing in a pointer
for data to be returned. I assumed that was what Maxime was referring to.

ChenYu

> >
> > ChenYu
> >
> > > The rest of the series is
> > > Acked-by: Maxime Ripard <mripard@...nel.org>
>
> Thanks!
>
> Best regards,
> Jernej
>
> > >
> > > Maxime
>
>
>
>