linux-kernel - Re: [PATCH v3] x86: sysfb: remove sysfb when probing real hw

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Date:	Thu, 19 Dec 2013 18:09:27 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	David Herrmann <dh.herrmann@...il.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Takashi Iwai <tiwai@...e.de>,
	Stephen Warren <swarren@...dotorg.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	"linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	stable <stable@...r.kernel.org>
Subject: Re: [PATCH v3] x86: sysfb: remove sysfb when probing real hw


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

> Hi
> 
> On Thu, Dec 19, 2013 at 5:36 PM, Ingo Molnar <mingo@...nel.org> wrote:
> >
> > * David Herrmann <dh.herrmann@...il.com> wrote:
> >
> >> --- a/drivers/video/fbmem.c
> >> +++ b/drivers/video/fbmem.c
> >> @@ -35,6 +35,9 @@
> >>
> >>  #include <asm/fb.h>
> >>
> >> +#if IS_ENABLED(CONFIG_X86)
> >> +#include <asm/sysfb.h>
> >> +#endif
> >
> > I think this can be written as:
> >
> > #ifdef CONFIG_X86
> > # include <asm/sysfb.h>
> > #endif
> >
> > also ... the dependency on a large, unrelated option like CONFIG_X86
> > looks pretty ugly here - is there no other, more specific CONFIG_
> > option that can be used here - such as CONFIG_FB_SIMPLE or
> > CONFIG_X86_SYSFB?
> >
> >> +#if IS_ENABLED(CONFIG_X86)
> >> +     sysfb_unregister(apert, primary);
> >> +#endif
> >
> > Ditto.
> 
> CONFIG_X86 is probably never 'm'.. will fix that. It was 
> CONFIG_X86_SYSFB before and that works, too, but the broader X86 
> seemed more appropriate as sysfb is available on all x86.

Well, sysfb is available if CONFIG_X86_SYSFB is set, right? So on 
!CONFIG_X86_SYSFB x86 kernels this code should not run, right?

> Note that I have patches here locally which move 
> sysfb_register/unregister to drivers/video/sysfb.c and add 
> include/linux/sysfb.h with dummies if CONFIG_SYSFB is not selected 
> to avoid the #ifdef. This will allow other architectures to do 
> gfx-hand-over, too. They seem too big for stable, though. That's why 
> I split them up and added it to x86/kernel/sysfb.c first.

Yeah, it's fine to do those cleanups after the minimal fix. But using 
a sensible config option must still be done - we cannot just slap 
broad CONFIG_X86 dependencies into random code.

Thanks,

	Ingo
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