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

# Re: RFC: Devices, buses and hotplug

David S. Miller (davem@redhat.com)
Sun, 6 Jun 1999 11:21:00 -0700

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Date: Sun, 06 Jun 1999 13:53:51 -0400
From: Jeff Garzik <jgarzik@pobox.com>

This is also very valuable. The newer S3 cards (and others as well)
fully support big endian as well as little endian, and it would be nice
to avoid the byteswapping that occurs in some current read*()
implementations, such as on PPC (and Sparc too?).

No, it is invaluable and leads to sloppy and inconsistant coding.

Byte swapping happens transparently on Sparc for PCI devices, the
normal read{b,w,l}() etc. interfaces are used for everything and it
just works.

It works because we architected Sparc to map PCI areas in the proper
endianness.

The end result is that you should not need "big endian" supporting
PCI devices, and in fact I consider such devices silly. Little endian
is the native PCI byte ordering, and any worthwhile architecture we
care about has hardware facilities to make them accessible at zero
cost (either via MMU mappings of device areas, or endianness
attributes in the load/store instructions themselves).

In general, when you start seeing a lot of "knobs" in an interface, it
starts to enter ugly territory, let's avoid ending up with a mess like
Solaris's DDI ok? :-)

Later,
David S. Miller
davem@redhat.com

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- Next message: Jeff Garzik: "[patch] Riva framebuffer driver (non-working)"
- Previous message: Matthew Kirkwood: "Re: ELOOP help needed"
- Maybe in reply to: Martin Mares: "RFC: Devices, buses and hotplug"
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- Reply: Jes Sorensen: "Re: RFC: Devices, buses and hotplug"