linux-kernel - Re: [PATCH] olpc: fix model detection without OFW

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Date:	Sat, 14 Feb 2009 23:14:29 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Andres Salomon <dilinger@...ued.net>
Cc:	Chris Ball <cjb@...top.org>,
	Harvey Harrison <harvey.harrison@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] olpc: fix model detection without OFW


* Andres Salomon <dilinger@...ued.net> wrote:

> On Sat, 14 Feb 2009 22:43:12 +0100
> Ingo Molnar <mingo@...e.hu> wrote:
> [...]
> > 
> > Applied to tip:x86/urgent [for v2.6.29], thanks guys!
> > 
> > Did i get the impact-line below right?
> > 
> > 	Ingo
> > 
> 
> More like -
> 
> Impact: garbled display, laptop is unusable
> 
> ;)

ah, okay :-) Serious regression that warrants urgent upstream routing.

> The DCON detection code determines whether there's a DCON attached
> based upon the model (any XO model >= B2 is assumed to have a DCON).
> The LXFB driver determines which mode to use based upon whether or not
> it thinks there's a DCON attached, and the DCON/LXFB can't deal w/
> standard modes.
> 
> So, the result is that LXFB attempts to use some random standard mode
> rather than the DCON-required 1200x900, and the display is unusable.

Where did my git grepping skills go wrong?

I git-grepped the code and this is the scope i found:

olpc_platform_info.boardrev is used for:

 - a printk
 - olpc_board_at_least() which is used in:
    - drivers/input/mouse/hgpk.c:                mouse driver quirk
    - sound/pci/cs5535audio/cs5535audio_olpc.c:  audio quirk

aha. I missed this roundabout impact:

    - arch/x86/kernel/olpc.c:                    OLPC_F_DCON flag
      - which is used in olpc_has_dcon(), which is used in:
        - drivers/video/geode/gxfb_core.c:       GX modes db
                                                 [ouch if this goes wrong!]
        - drivers/video/geode/lxfb_core.c:       ditto

So i guess the mouse and audio quirk point was correct too, but the
major impact is the graphics mode array mismatch and the resulting
nonsensical mode setting, right?

	Ingo
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