Re: [PATCH 5.10 28/63] fbcon: Disable accelerated scrolling

Geert Uytterhoeven
2021-01-07T08:14:18Z

On Mon, Jan 4, 2021 at 5:58 PM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
> From: Daniel Vetter <daniel.vetter@ffwll.ch>
>
> commit 39aead8373b3c20bb5965c024dfb51a94e526151 upstream.
>
> So ever since syzbot discovered fbcon, we have solid proof that it's
> full of bugs. And often the solution is to just delete code and remove
> features, e.g. 50145474f6ef ("fbcon: remove soft scrollback code").
>
> Now the problem is that most modern-ish drivers really only treat
> fbcon as an dumb kernel console until userspace takes over, and Oops
> printer for some emergencies. Looking at drm drivers and the basic
> vesa/efi fbdev drivers shows that only 3 drivers support any kind of
> acceleration:
>
> - nouveau, seems to be enabled by default
> - omapdrm, when a DMM remapper exists using remapper rewriting for
> y/xpanning
> - gma500, but that is getting deleted now for the GTT remapper trick,
> and the accelerated copyarea never set the FBINFO_HWACCEL_COPYAREA
> flag, so unused (and could be deleted already I think).
>
> No other driver supportes accelerated fbcon. And fbcon is the only

Note that there are 32 more drivers using acceleration under
drivers/video/fbdev/.

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