linux-kernel - Re: cirrusdrmfb broken with simplefb

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Message-ID: <20131219124417.GA18305@gmail.com>
Date:	Thu, 19 Dec 2013 13:44:17 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	David Herrmann <dh.herrmann@...il.com>
Cc:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Takashi Iwai <tiwai@...e.de>,
	Stephen Warren <swarren@...dotorg.org>,
	"linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>
Subject: Re: cirrusdrmfb broken with simplefb


* David Herrmann <dh.herrmann@...il.com> wrote:

> Hi
> 
> On Thu, Dec 19, 2013 at 1:31 PM, Ingo Molnar <mingo@...nel.org> wrote:
> >
> > * David Herrmann <dh.herrmann@...il.com> wrote:
> >
> >> Hi
> >>
> >> On Thu, Dec 19, 2013 at 1:03 AM, One Thousand Gnomes
> >> <gnomes@...rguk.ukuu.org.uk> wrote:
> >> >> > That bug always existed, simplefb is just the first driver to hit it
> >> >> > (vesafb/efifb didn't use resources). I'm aware of the issue but as a
> >> >> > workaround you can simply disable CONFIG_X86_SYSFB. That restores
> >> >> > the old behavior.
> >> >>
> >> >> This looks like a regression, so we'll either need a fix or we'll have
> >> >> to mark CONFIG_X86_SYSFB as CONFIG_BROKEN.
> >> >
> >> > Kernel bugzilla has entries for simplefb breaking both vesafb and
> >> > matrox mga.
> >>
> >> Thanks for the hints. I've read through all I could find and tried
> >> to provide some help.
> >>
> >> I'm kind of confused, most of them enable CONFIG_X86_SYSFB (which is
> >> 'n' by default) but don't read the help text. I did my best to tell
> >> people that this option requires CONFIG_FB_SIMPLE, but if you don't
> >> read the help-text you won't notice that. Don't know what to do
> >> about that..
> >
> > People generally don't read the help text - still the kernel should
> > not break. So please the Kconfig angle (and the bootup logic, etc.)
> > fool-proof, graphics failures are not fun to debug!
> 
> There're dozens of combinations that break gfx-boot. [...]

Then that's a bug too.

> [...] Even non-obvious things like disabling VT_HW_CONSOLE_BINDING 
> will break gfx-handover. Anyhow, bad examples are no excuse.. I will 
> send patches to fool-proof sysfb.

Cool, thanks!

Arguably there's a lot of broken gfx legacy in Linux.

<SoapBox>: 15 years ago we should have merged GGI that really got the 
integrated gfx principles right from the get go IMHO - and we've been 
struggling with fragmented, disjunct gfx concepts since then, but IMHO 
it's getting better gradually, so please don't give up! ;-)

	Ingo
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