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Date: Thu, 19 Dec 2013 12:06:53 +0100
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From: Takashi Iwai <tiwai@suse.de>
To: David Herrmann <dh.herrmann@gmail.com>
Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>,
        Ingo Molnar <mingo@kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Stephen Warren <swarren@wwwdotorg.org>,
        "linux-fbdev@vger.kernel.org" <linux-fbdev@vger.kernel.org>,
        "the arch/x86 maintainers" <x86@kernel.org>
Subject: Re: cirrusdrmfb broken with simplefb
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At Thu, 19 Dec 2013 11:46:51 +0100,
David Herrmann wrote:
> 
> Hi
> 
> On Thu, Dec 19, 2013 at 1:03 AM, One Thousand Gnomes
> <gnomes@lxorguk.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..

You can set FB_SIMPLE default value depending on X86_SYSFB, something
like:

--- a/drivers/video/Kconfig
+++ b/drivers/video/Kconfig
@@ -2455,6 +2455,7 @@ config FB_HYPERV
 config FB_SIMPLE
 	bool "Simple framebuffer support"
 	depends on (FB = y)
+	default y if X86_SYSFB
 	select FB_CFB_FILLRECT
 	select FB_CFB_COPYAREA
 	select FB_CFB_IMAGEBLIT


Takashi