PIO port width on various archs?

PIO port width on various archs?

[Avi Kivity]

I'm changing the kvm userspace interface to be more friendly to other 
archs.  One issue is the PIO port size.  x86 uses 16 bits to hold the 
port size (64K ports).  Is that an issue for other archs?

I guess I could change it to __u32, but it's better to know what various 
architectures actually require.

-- 
error compiling committee.c: too many arguments to function


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Re: PIO port width on various archs?

[Hollis Blanchard]

On Sun, 2007-02-25 at 10:58 +0200, Avi Kivity wrote:
> I'm changing the kvm userspace interface to be more friendly to other 
> archs.  One issue is the PIO port size.  x86 uses 16 bits to hold the 
> port size (64K ports).  Is that an issue for other archs?
> 
> I guess I could change it to __u32, but it's better to know what various 
> architectures actually require.

PowerPC doesn't have any such concept; access to ISA PIO is done by
having the bridge translate a particular range of MMIO accesses as PIO.
I'm no expert, but I don't know of any mainstream processor other than
x86 that supports PIO.

-Hollis


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Re: PIO port width on various archs?

[Avi Kivity]

Hollis Blanchard wrote:
> On Sun, 2007-02-25 at 10:58 +0200, Avi Kivity wrote:
>   
>> I'm changing the kvm userspace interface to be more friendly to other 
>> archs.  One issue is the PIO port size.  x86 uses 16 bits to hold the 
>> port size (64K ports).  Is that an issue for other archs?
>>
>> I guess I could change it to __u32, but it's better to know what various 
>> architectures actually require.
>>     
>
> PowerPC doesn't have any such concept; access to ISA PIO is done by
> having the bridge translate a particular range of MMIO accesses as PIO.
> I'm no expert, but I don't know of any mainstream processor other than
> x86 that supports PIO.
>
>   

I think ia64 does, but it's probably exactly the same as x86.


-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.


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Re: PIO port width on various archs?

[Brian Johnson]

Avi Kivity wrote:
> Hollis Blanchard wrote:
>> On Sun, 2007-02-25 at 10:58 +0200, Avi Kivity wrote:
>>   
>>> I'm changing the kvm userspace interface to be more friendly to other 
>>> archs.  One issue is the PIO port size.  x86 uses 16 bits to hold the 
>>> port size (64K ports).  Is that an issue for other archs?
>>>
>>> I guess I could change it to __u32, but it's better to know what various 
>>> architectures actually require.
>>>     
>> PowerPC doesn't have any such concept; access to ISA PIO is done by
>> having the bridge translate a particular range of MMIO accesses as PIO.
>> I'm no expert, but I don't know of any mainstream processor other than
>> x86 that supports PIO.
>>   
> 
> I think ia64 does, but it's probably exactly the same as x86.

IA64 uses a special memory range which is translated into I/O port 
accesses by the CPU hardware (as opposed to the I/O bridge.)  Section 
10.7 of volume 2 of the Itanium SDM has the details.  Only 64k of I/O 
ports is supported.

Brian J. Johnson

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