Re: My penguin has blue feets (aka: RGB versus BGR troubles)

[Sam Ravnborg <sam@ravnborg.org>]

Hi Daniel.

> > >
> > > *Any* hints why modetest fails when my driver reports the correct formats?
> >
> > Every driver to date supports XR24. So modetest uses that by default.
> > But this fails with your driver since it's an unsupported format.
> > Something like:
> >
> > modetest -M atmel-lcdc -s 34:800x480-60Hz@XB24
> >
> > should do the trick. The quirk covers drivers that use AddFB().
> > However modetest is fancy and uses AddFB2, which takes an explicit
> > format.
> 
> Yeah I thinki for fbdev the correct fix is to look whether the driver
> enabled atomic and if so, consult the fourcc format list of the
> primary plane of the first crtc to figure out what you might actually
> have set. Without atomic you can't realy on the format list being
> correct since for drivers who get the default primary plane that
> drm_crtc_init sets up the format list is garbage.

I do not follow you here.

# modetest -M atmel-lcdc -p
Planes:
id      crtc    fb      CRTC x,y        x,y     gamma size      possible crtcs
31      32      35      0,0             0,0     0               0x00000001
  formats: XB24 BG24 BG16

# modetest -M atmel-lcdc -a -p
Planes:
id      crtc    fb      CRTC x,y        x,y     gamma size      possible crtcs
31      32      35      0,0             0,0     0               0x00000001
  formats: XB24 BG24 BG16

So with or without atomic (-a option) the driver reports the same formats.


# modetest -M atmel-lcdc -a -s ...

does not work btw. It just exists without anything shown on the panel.


> Reworking the entire
> fbdev emulation to use fourcc codes would be even more awesome I
> guess.
To take the bait I would need a little bit more guidiance on this.

Is it something like:
- New variant af drm_fbdev_generic_setup() that takes a fourcc code, not
  a preferred_bpp
- drm_fb_helper_initial_config likewise
- drm_fb_helper_fbdev_setup likewise
- drm_fb_helper_single_fb_probe likewise

And then work through all the code until we no longer rely on
preferred_bpp??

	Sam
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