DRM_CAS bug with x86_64

[Ian Romanick]

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Alan Coopersmith wrote:
> Ian Romanick wrote:
>> Bernardo Innocenti wrote:
>>
>>> GAS choked on the DRM_CAS invocation in ffb_lock.h because
>>> __ret was declared as "int" and so it gets passed in %edx
>>> instead of %dl or %dh as required by the setnz instruction.
>>> I just wrapped the declaration with DRM_CAS_RESULT() as done
>>> elsewhere.
>>
>> This seems to have never hit us because on x86 the FFB driver no-ops its
>> LOCK_HARDWARE and UNLOCK_HARDWARE macros.  Can somebody please explain
>> why that is?  My *guess* is that FFB hardware can only actually exist on
>> SPARC.
> 
> I was wondering why ffb was even being built on x86_64.   If it's referring
> to the board from Sun (which marketing called a "Creator" or "Creator 3D"),
> it was only ever made for the UPA bus (UltraSPARC Port Architecture), not
> PCI or any other common bus, and I've never seen a UPA bus outside of a
> SPARC machine.

The irony is that it gets built on non-SPARC platforms so that we'll
know right away if a change has broken its build.  He had cases in the
past where changes that broke the ffb build went *6 months* without
being noticed.
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