Re: [PATCH 6/7] sata_mv: endian fix

[Jeff Garzik <jgarzik@pobox.com>]

Zang Roy-r61911 wrote:
>> Zang Roy-r61911 wrote:
>>>> This fixes a byte-swap issue on PPC, found by Zang Roy-r61911
>>>> on the powerpc platform.  His original patch also had some other
>>>> platform-specific changes in #ifdef's, but I'm not sure yet how to
>>>> incorporate them.  Look for another patch for those (soon).
>>>>
>>>> Signed-off-by: Mark Lord <liml@rtr.ca>
>>>>
>>>> ---
>>>> --- linux/drivers/scsi/sata_mv.c	2006-05-19 
>>>> 15:44:11.000000000 -0400
>>>> +++ linux/drivers/scsi/sata_mv.c	2006-05-19 
>>>> 15:58:21.000000000 -0400
>>>> @@ -1030,8 +1030,9 @@
>>>>  
>>>>  static inline void mv_crqb_pack_cmd(u16 *cmdw, u8 data, u8 
>>>> addr, unsigned last)
>>>>  {
>>>> -	*cmdw = data | (addr << CRQB_CMD_ADDR_SHIFT) | CRQB_CMD_CS |
>>>> +	u16 tmp = data | (addr << CRQB_CMD_ADDR_SHIFT) | CRQB_CMD_CS |
>>>>  		(last ? CRQB_CMD_LAST : 0);
>>>> +	*cmdw = cpu_to_le16(tmp);
>>>>  }
>>>>  
>>>>  /**
>>>>
>>>
>>> Does this patch will affect other platform except powerpc?
>> This patch affects all platforms (as it should).  Most Linux code is 
>> intentionally written in a cross-platform, portable manner 
>> without ifdefs.
>>
>> 	Jeff
>>
>>
>>
> I can see it work on powerpc platform, while does it work for other 
> platform such as i386?

Yes.  Look at the definition of the function in question:  for little 
endian platforms, it is a simple assignment.  For big endian platforms, 
it does the expected byte swap.

This is also the standard for Linux code:  one function Does The Right 
Thing, regardless of platform.

	Jeff