From mboxrd@z Thu Jan  1 00:00:00 1970
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [Linux-fbdev-devel] Re: FB model basic issues (WAS: radeon,
	apertures & memory mapping)
Date: Thu, 17 Mar 2005 10:25:48 +1100
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To: Ville =?ISO-8859-1?Q?Syrj=E4l=E4?= <syrjala@sci.fi>
Cc: Linux Fbdev development list <linux-fbdev-devel@lists.sourceforge.net>, Michel =?ISO-8859-1?Q?D=E4nzer?= <michel@daenzer.net>, Jon Smirl <jonsmirl@yahoo.com>, xorg@lists.freedesktop.org, adaplas@pol.net, dri-devel@lists.sourceforge.net

On Wed, 2005-03-16 at 21:51 +0200, Ville Syrj=E4l=E4 wrote:

> This was about the DirectFB drivers.
>=20
> One thing just popped to my head though. If in the future we are going =
to=20
> allow graphics cards to render to system memory, using the swapper will=
 no=20
> longer work. I don't see any other solution that having the CPU perform=
=20
> the byte swapping.

There is a _lot_ of existing code that will stop working, MOL is an
example, it requires proper "native" format for the framebuffer. X too
in it's current incarnation (fb format is defined at compile time I
think).

So the swapper is _needed_ for framebuffer access.

The best we can do is save/change/restore it around accesses like we do
already when copying YUV frames to video memory.

Now regarding the setup of the apertures, I suppose that I'll do
something complicated that nobody will use right, that is use 2 separate
apertures contiguous with each framebuffer at the beginning of each
aperture when CONFIG_APER_SIZE is 1/2 of vram size, and 2 separate
apertures contiguous with each framebuffer together in the first one in
the other cases. Only difference: first case will allow macs to have
separate swappers for each aperture. All other cases will have both
swappers set the same way. Hopefully, all "Mac" cards have
CONFIG_APER_SIZE set to half the vram.

Ben.