Linux-kernel mailing list archive 1999-23,: Re: RFC: Devices, buses and hotplug

# Re: RFC: Devices, buses and hotplug

Paul Mackerras (paulus@cs.anu.edu.au)
Mon, 7 Jun 1999 15:35:34 +1000

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David S. Miller <davem@redhat.com> wrote:

> I never got down to facts about whether it was an issue of the PPC
> supporting it in HW or the PPC developers just mis-designed their
> framework and now require big endian friendly devices just to work.

PPC has byte-swapped load and store instructions, and the
in*/out*/read*/write* family of macros use them. It doesn't have the
endianness selectable on a per-page basis like the ultra does, where
you can do a normal load/store to a little-endian page and the
hardware byte-swaps it for you (if I've understood it correctly).

So if you have a frame buffer with multi-byte pixels, you can either
use a big-endian aperture if there is one, or have versions of all
your framebuffer access routines which use the byte-swapped loads and
stores instead of normal loads and stores. That would be possible
(and would even be just as fast) but it would be a little ugly.

Paul.

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- Next message: Shashank Banerjee: "UTIME patch"
- Previous message: James H. Cloos Jr.: "Re: [linux-usb] Re: [announce] Linux Input Driver suite version 0.1.0"
- Maybe in reply to: Martin Mares: "RFC: Devices, buses and hotplug"
- Next in thread: H. Peter Anvin: "Re: RFC: Devices, buses and hotplug"