[PATCH 1/5] powerpc: Use sg->dma_length in sg_dma_len() macro on 32-bit

[Becky Bruce]

On Apr 20, 2009, at 3:06 PM, Kumar Gala wrote:

>
> On Apr 20, 2009, at 11:26 AM, Becky Bruce wrote:
>
>> Currently, the 32-bit code uses sg->length instead of sg->dma_lentgh
>> to report sg_dma_len.  However, since the default dma code for 32-bit
>> (the dma_direct case) sets dma_length and length to the same thing,
>> we should be able to use dma_length there as well.  This gets rid of
>> some 32-vs-64-bit ifdefs, and is needed by the swiotlb code which
>> actually distinguishes between dma_length and length.
>>
>> Signed-off-by: Becky Bruce <beckyb at kernel.crashing.org>
>> ---
>> arch/powerpc/include/asm/scatterlist.h |    6 +-----
>> 1 files changed, 1 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/scatterlist.h b/arch/powerpc/ 
>> include/asm/scatterlist.h
>> index fcf7d55..912bf59 100644
>> --- a/arch/powerpc/include/asm/scatterlist.h
>> +++ b/arch/powerpc/include/asm/scatterlist.h
>> @@ -21,7 +21,7 @@ struct scatterlist {
>> 	unsigned int offset;
>> 	unsigned int length;
>
> can we get rid of length?

No - they're both used by the iotlb code and are conceptually  
different.  "dma_length" can get set to less than "length" to indicate  
that something went wrong with a dma request - the iotlb code sets it  
to 0 if we can't allocate a bounce buffer, for example.  It probably  
has other uses as well - this is just the one I'm familiar with.  In  
most cases they are equal.

Cheers,
B