linux-kernel - Re: [PATCH] offb: Fix little-endian support

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Message-ID: <s5hwqcfdfdm.wl%tiwai@suse.de>
Date:	Tue, 17 Jun 2014 12:01:09 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	Tomi Valkeinen <tomi.valkeinen@...com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Cedric Le Goater <clg@...ibm.com>,
	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] offb: Fix little-endian support

At Tue, 17 Jun 2014 09:54:07 +1000,
Benjamin Herrenschmidt wrote:
> 
> On Mon, 2014-06-16 at 17:35 +1000, Benjamin Herrenschmidt wrote:
> 
> > I somewhat doubt that this (and 5:5:5) actually work, do they ? the
> > green gets split into two separate fields, which we can't express
> > properly here...
> 
> So the conclusion of further investigation is:
> 
>  - The right fix is to fix qemu to flip endian
> 
>  - There's an open discussion as to whether qemu could do it
> automatically when the guest endian changes on powerpc as a quick fix,
> the long run approach is to have a register to control it, I'm working
> on it. offb can then "learn" to flick it like it does the palette hack
> today.
> 
>  - If we want to ever support foreign endian offb with X, we need to do
> things a bit differently based on the foreign endian bit that is already
> there.
> 
>  - We must revert the existing cmap swap patch from the kernel, it's
> broken and will break things when we fix qemu (and breaks with real HW
> in LE mode). I've sent a revert request to Linus and CC'ed stable.

Yeah, I agree.  Both the current palette fix and my patch are really
wrong band-aiding.

(Though, the issue in X is rather a problem of X itself.  X should
 work with the tweaked RGB offsets.)


thanks,

Takashi
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