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Date:   Tue, 18 Jan 2022 07:11:20 +0100
From:   Gerd Hoffmann <kraxel@redhat.com>
To:     Geert Uytterhoeven <geert@linux-m68k.org>
Cc:     Helge Deller <deller@gmx.de>, Daniel Vetter <daniel@ffwll.ch>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        "airlied@gmail.com" <airlied@gmail.com>,
        Linux Fbdev development list <linux-fbdev@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        DRI Development <dri-devel@lists.freedesktop.org>,
        Javier Martinez Canillas <javierm@redhat.com>
Subject: Re: [PATCH] MAINTAINERS: Add Helge as fbdev maintainer
Message-ID: <20220118061120.7exr5vtdwyuzhnup@sirius.home.kraxel.org>
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On Mon, Jan 17, 2022 at 02:29:47PM +0100, Geert Uytterhoeven wrote:
> Hi Gerd,
> 
> On Mon, Jan 17, 2022 at 1:57 PM Gerd Hoffmann <kraxel@redhat.com> wrote:
> > > b) to include new drivers (for old hardware) if they arrive (probably happens rarely but there can be).
> > >    I know of at least one driver which won't be able to support DRM....
> >
> > Hmm?  I seriously doubt that.  There is always the option to use a
> > shadow framebuffer, then convert from standard drm formats to whatever
> > esoteric pixel format your hardware expects.
> >
> > Been there, done that.  Have a look at the cirrus driver.  The physical
> > hardware was designed in the early 90-ies, almost 30 years ago.  These
> > days it exists in virtual form only (qemu emulates it).  Thanks to the
> > drm driver it runs wayland just fine even though it has a bunch of
> > constrains dictated by the hardware design.
> 
> The Cirrus DRM driver supports TrueColor (RGB565/888 and ARGB8888)
> modes only.  The Cirrus fbdev driver also supports mochrome and 256
> color modes.
> 
> There exist some DRM drivers that do support DRM_FORMAT_C8, but none of
> the "tiny" ones do. Same for DRM_FORMAT_RGB{332,233}.

Adding that to the cirrus driver shouldn't be hard.  I'm wondering
whenever there are any userspace apps which would actually use that
though.

take care,
  Gerd