Re: Proposals to change the way all drivers work with SCSI commands

[Heiko Carstens <heiko.carstens@de.ibm.com>]

On Fri, May 11, 2007 at 01:33:41PM -0500, James Bottomley wrote:
> It strikes me that in all of this, we could also consider doing the DMA
> mapping inside the mid layer (instead of in every driver).  This is
> essentially what libata is already doing ... leading to confusion in
> SCSI drivers that use libata for SATA.
> 
> So what do people think about this?

I hope that doesn't mean that each architecture is required to
implement all the DMA mapping stuff? s390 doesn't have any support
for DMA at all. The current workaround seems to be to sprinkle
a lot of BUG() statements in code that simply won't work on such
architectures but still compile it in.
Lately I introduced CONFIG_HAS_DMA and made building
drivers/base/dma-mapping.o and dmapool.o depend on that,
so we don't compile all the non working stuff on s390. Hope
all that can be sorted out if you go that direction.