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    SubjectRe: [Linux-fbdev-devel] [PATCH 1/2] fb: add support for foreign endianness
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    On Tue, 2008-02-19 at 00:35 +0100, Clemens Koller wrote:
    > Valdis.Kletnieks@vt.edu schrieb:
    > > On Mon, 18 Feb 2008 08:18:47 +0100, Krzysztof Helt said:
    > >> I know two fb drivers which use endianess information (pm2fb and s3c2410fb).
    > >> Both resolve endianess at driver level. Actually, both handle it by setting special
    > >> bits so the graphics chip itself reorder bytes to transform foreign endianess.
    > >> I understand that this patch is for chips which cannot reorder bytes by themselves.
    > >
    > > Does anybody know of such a chip that's actually available in the wild? Or are
    > > we writing drivers for speculative possible chips?
    > >
    >
    > I had troubles with the Silicon Motion SM501/SM502 endianess on PowerPC PCI vs. LocalBus.
    > The chip also has a register to swap endianess, but that seems to only affect some
    > LocalBus modes.
    > The current fb and X drivers are working, but when it comes to font
    > aliasing and hw-acceleration, the problems start to rise again...

    Most "sane" gfx chips nowadays provide configurable surfaces that allow
    to perform the swap when writing/reading from regions of the
    framebuffer, with the ability to set a different swapper setting (based
    on bit depth) per region.

    Then there is also the risk that your PCI<->Localbus has been wired
    improperly :-)

    Ben.




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