Re: [PATCH v2 04/10] drm/simpledrm: Compute framebuffer stride if not set

[Thomas Zimmermann <tzimmermann@xxxxxxx>]

Am 11.08.22 um 20:26 schrieb Thomas Zimmermann:
> Hi Daniel
>
> Am 11.08.22 um 19:23 schrieb Daniel Vetter:
> > On Wed, 27 Jul 2022 at 09:53, Thomas Zimmermann <tzimmermann@xxxxxxx> 
> > wrote:
> > > Hi
> > >
> > > Am 25.07.22 um 17:13 schrieb Javier Martinez Canillas:
> > > > Hello Geert,
> > > >
> > > > On 7/21/22 16:46, Geert Uytterhoeven wrote:
> > > > > Hi Thomas,
> > > > >
> > > > > On Wed, Jul 20, 2022 at 4:27 PM Thomas Zimmermann 
> > > > > <tzimmermann@xxxxxxx> wrote:
> > > > > > Compute the framebuffer's scanline stride length if not given by
> > > > > > the simplefb data.
> > > > > >
> > > > > > Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
> > > > >
> > > > > Thanks for your patch!
> > > > >
> > > > > > --- a/drivers/gpu/drm/tiny/simpledrm.c
> > > > > > +++ b/drivers/gpu/drm/tiny/simpledrm.c
> > > > > > @@ -743,6 +743,9 @@ static struct simpledrm_device 
> > > > > > *simpledrm_device_create(struct drm_driver *drv,
> > > > > >                   drm_err(dev, "no simplefb configuration found\n");
> > > > > >                   return ERR_PTR(-ENODEV);
> > > > > >           }
> > > > > > +       if (!stride)
> > > > > > +               stride = format->cpp[0] * width;
> > > > >
> > > > > DIV_ROUND_UP(drm_format_info_bpp(format) * width, 8)
> > > >
> > > > I think you meant here:
> > > >
> > > > DIV_ROUND_UP(drm_format_info_bpp(format, 0) * width, 8) ?
> > >
> > > I guess, that's the right function. My original code is correct, but cpp
> > > is also deprecated.
> >
> > You all mean drm_format_info_min_pitch().
>
> Thanks a lot. I wasn't even aware of this function, but I had almost 
> written my own implementation of it.  I'll update the patch accordingly.

Arghh, too late. I merged that patch already.

> Best regards
> Thomas
>
> > I really don't want drivers to go grab any of the legacy format info
> > fields like bpp or depth. switch() statements on the fourcc code for
> > programming registers, or one of the real helper functions in
> > drm_fourcc.c (there might be some gaps), but not ever going through
> > legacy concepts. Anything else just leads to subtle bugs when new
> > formats get added and oops suddenly the assumptions don't hold.
> >
> > Those should be strictly limited to legacy (i.e. not drm_fourcc aware)
> > interfaces. Heck I think even fbdev emulation should completely switch
> > over to drm_fourcc/drm_format_info, but alas that's a pile of work and
> > not much payoff.
> >
> > I'm trying to volunteer Same to add a legacy_bpp tag to the above
> > helper and appropriately limit it, I think limiting to formats with
> > depth!=0 is probably the right thing. And then we should probably
> > remove a pile of the cargo-culted depth!=0 entries too.
> > -Daniel
> >
> > > Best regards
> > > Thomas
> > >
> > > > With that change,
> > > >
> > > > Acked-by: Javier Martinez Canillas <javierm@xxxxxxxxxx>
> > >
> > > --
> > > Thomas Zimmermann
> > > Graphics Driver Developer
> > > SUSE Software Solutions Germany GmbH
> > > Maxfeldstr. 5, 90409 Nürnberg, Germany
> > > (HRB 36809, AG Nürnberg)
> > > Geschäftsführer: Ivo Totev

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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