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

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Message-ID: <1402962847.7661.82.camel@pasglop>
Date:	Tue, 17 Jun 2014 09:54:07 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Takashi Iwai <tiwai@...e.de>
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

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.

Cheers,
Ben.


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