On Wed, Oct 24 2007, FUJITA Tomonori wrote:
quoted text
> On Wed, 24 Oct 2007 07:39:16 -0400
> Jeff Garzik <jeff@garzik.org> wrote:
> 
> > FUJITA Tomonori wrote:
> > > request_queue and device struct must have the same value of a segment
> > > size limit. This patch adds blk_queue_segment_boundary in
> > > __scsi_alloc_queue so LLDs don't need to call both
> > > blk_queue_segment_boundary and set_dma_max_seg_size. A LLD can change
> > > the default value (64KB) can call device_dma_parameters accessors like
> > > pci_set_dma_max_seg_size when allocating scsi_host.
> > > 
> > > Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
> > > ---
> > >  drivers/scsi/scsi_lib.c |    3 +++
> > >  1 files changed, 3 insertions(+), 0 deletions(-)
> > > 
> > > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> > > index 61fdaf0..23a30ab 100644
> > > --- a/drivers/scsi/scsi_lib.c
> > > +++ b/drivers/scsi/scsi_lib.c
> > > @@ -1645,6 +1645,7 @@ struct request_queue *__scsi_alloc_queue(struct Scsi_Host *shost,
> > >  					 request_fn_proc *request_fn)
> > >  {
> > >  	struct request_queue *q;
> > > +	struct device *dev = shost->shost_gendev.parent;
> > >  
> > >  	q = blk_init_queue(request_fn, NULL);
> > >  	if (!q)
> > > @@ -1673,6 +1674,8 @@ struct request_queue *__scsi_alloc_queue(struct Scsi_Host *shost,
> > >  	blk_queue_bounce_limit(q, scsi_calculate_bounce_limit(shost));
> > >  	blk_queue_segment_boundary(q, shost->dma_boundary);
> > >  
> > > +	blk_queue_max_segment_size(q, dma_get_max_seg_size(dev));
> > > +
> > 
> > it would be nice to have something more general that's useable in 
> > drivers/block/sx8.c (for example), something like
> > 
> > 	static inline void
> > 	dev_blk_associate(struct device *dev, request_queue *q)
> > 	{
> > 		blk_queue_max_segment_size(q,
> > 					dma_get_max_seg_size(dev));
> > 	}
> > 
> > still, I will ACK the above patch (#9) in case you wish that to become a 
> > future cleanup, or others dislike this suggestion
> 
> Yeah, I thought about something like that. But I can't find many
> non-scsi drivers (ide, sx8, mmc/card/, anymore?) doing dma and having
> the restrictions so I just call blk_queue_max_segment_size here.
> 
> Either is ok with me. I'll modify the patch if Jens prefers such
> function. Jens?

If there's a use for it, sure.

-- 
Jens Axboe

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