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From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: Thomas Zimmermann <tzimmermann@suse.de>,
	David Airlie <airlied@linux.ie>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Maxime Ripard <mripard@kernel.org>,
	Gerd Hoffmann <kraxel@redhat.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Liam Girdwood <lgirdwood@gmail.com>,
	Mark Brown <broonie@kernel.org>, Sam Ravnborg <sam@ravnborg.org>,
	Rob Herring <robh@kernel.org>,
	Emil Velikov <emil.l.velikov@gmail.com>,
	Hans de Goede <hdegoede@redhat.com>,
	bluescreen_avenger@verizon.net,
	Greg KH <gregkh@linuxfoundation.org>,
	DRI Development <dri-devel@lists.freedesktop.org>,
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	virtualization@lists.linux-foundation.org
Subject: Re: [PATCH v4 0/9] drm: Support simple-framebuffer devices and firmware fbs
Date: Tue, 20 Apr 2021 11:16:09 +0200
Message-ID: <CAMuHMdU7BXN0P29wqWo2w3BWr=vQ=UHZHUnfFbMC--29ZBph-w@mail.gmail.com> (raw)
In-Reply-To: <YH6U92Q71ntU6Z1R@phenom.ffwll.local>

Hi Daniel,

On Tue, Apr 20, 2021 at 10:46 AM Daniel Vetter <daniel@ffwll.ch> wrote:
> On Mon, Apr 19, 2021 at 10:00:56AM +0200, Geert Uytterhoeven wrote:
> > On Fri, Apr 16, 2021 at 11:00 AM Thomas Zimmermann <tzimmermann@suse.de> wrote:
> > > This patchset adds support for simple-framebuffer platform devices and
> > > a handover mechanism for native drivers to take-over control of the
> > > hardware.
> > >
> > > The new driver, called simpledrm, binds to a simple-frambuffer platform
> > > device. The kernel's boot code creates such devices for firmware-provided
> > > framebuffers, such as EFI-GOP or VESA. Typically the BIOS, UEFI or boot
> > > loader sets up the framebuffers. Description via device tree is also an
> > > option.
> >
> > I guess this can be used as a replacement for offb, too...
> >
> > > Patches 4 to 8 add the simpledrm driver. It's build on simple DRM helpers
> > > and SHMEM. It supports 16-bit, 24-bit and 32-bit RGB framebuffers. During
> >
> > .... if support for 8-bit frame buffers would be added?
>
> Is that 8-bit greyscale or 8-bit indexed with 256 entry palette? Former

8-bit indexed with 256 entry palette.

> shouldn't be a big thing, but the latter is only really supported by the
> overall drm ecosystem in theory. Most userspace assumes that xrgb8888
> works, and we keep that illusion up by emulating it in kernel for hw which
> just doesn't support it. But reformatting xrgb8888 to c8 is tricky at
> best. The uapis are all there for setting the palette, and C8 is a defined
> format even with atomic kms interface, but really there's not much
> userspace for it. In other words, it would work as well as current offb
> would, but that's at least that.

Oh, that's good to know!
Does this mean fbdev is not deprecated for anything <= C8? ;-)

A while ago, I was looking into converting an fbdev driver to drm, and
one of the things I ran into is lack of C4, C2, C1, Y8, Y4, Y2, and
monochrome support.  On top of that, lots of internal code seems to
assume pixels are never smaller than a byte (thus ignoring
char_per_block[]/block_w).  The lack of support for planar modes isn't
that bad, combined with the need for copying, as c2p conversion can be
done while copying, thus even making life easier for userspace
applications that can just always work on chunky data.
Then real work kicked in, before I got anything working...

Thanks!

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

  reply index

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-16  9:00 Thomas Zimmermann
2021-04-16  9:00 ` [PATCH v4 1/9] drm/format-helper: Pass destination pitch to drm_fb_memcpy_dstclip() Thomas Zimmermann
2021-04-16  9:00 ` [PATCH v4 2/9] drm/format-helper: Add blitter functions Thomas Zimmermann
2021-04-16  9:00 ` [PATCH v4 3/9] drm/aperture: Add infrastructure for aperture ownership Thomas Zimmermann
2021-04-16  9:00 ` [PATCH v4 4/9] drm: Add simpledrm driver Thomas Zimmermann
2021-04-16  9:00 ` [PATCH v4 5/9] drm/simpledrm: Add fbdev emulation Thomas Zimmermann
2021-04-16  9:00 ` [PATCH v4 6/9] drm/simpledrm: Initialize framebuffer data from device-tree node Thomas Zimmermann
2021-04-16  9:00 ` [PATCH v4 7/9] drm/simpledrm: Acquire clocks from DT device node Thomas Zimmermann
2021-04-16  9:00 ` [PATCH v4 8/9] drm/simpledrm: Acquire regulators " Thomas Zimmermann
2021-04-16  9:00 ` [PATCH v4 9/9] drm/simpledrm: Acquire memory aperture for framebuffer Thomas Zimmermann
2021-04-19  8:00 ` [PATCH v4 0/9] drm: Support simple-framebuffer devices and firmware fbs Geert Uytterhoeven
2021-04-20  8:46   ` Daniel Vetter
2021-04-20  9:16     ` Geert Uytterhoeven [this message]
2021-04-20 11:11       ` Daniel Vetter
2021-04-20  9:22     ` Gerd Hoffmann
2021-04-20  9:27       ` Geert Uytterhoeven
2021-04-26 12:22         ` Thomas Zimmermann
2021-04-26 19:05           ` Geert Uytterhoeven
2021-04-26 12:18     ` Thomas Zimmermann
2021-04-26 15:08       ` Daniel Vetter
2021-04-29 10:24 ` Maxime Ripard

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