Re: [Qemu-devel] Re: [PATCH 1/3] kvm-unit-tests: add x86 port io accessors

[Avi Kivity <avi@redhat.com>]

On 02/27/2011 04:01 PM, Anthony Liguori wrote:
> On 02/27/2011 06:44 AM, Avi Kivity wrote:
>> On 02/24/2011 11:48 PM, Anthony Liguori wrote:
>>> Signed-off-by: Anthony Liguori<aliguori@us.ibm.com>
>>>
>>> diff --git a/lib/x86/io.h b/lib/x86/io.h
>>> new file mode 100644
>>> index 0000000..bd6341c
>>> --- /dev/null
>>> +++ b/lib/x86/io.h
>>> @@ -0,0 +1,40 @@
>>> +#ifndef IO_H
>>> +#define IO_H
>>> +
>>> +static inline unsigned char inb(unsigned short port)
>>> +{
>>> +    unsigned char value;
>>> +    asm volatile("inb %w1, %0" : "=a" (value) : "Nd" (port));
>>> +    return value;
>>> +}
>>
>> Are those %[wb] really needed?  gcc should do the right thing based 
>> on the argument type.
>
> It's just a little extra type safety.

Yeah, but those constraints aren't really documented.  Linux does use 
them in a handful of places so they're unlikely to go away though.

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