On Thu, 27 Sep 2007 02:31:14 -0400
Jeff Garzik <jeff@xxxxxxxxxx> wrote:
> FUJITA Tomonori wrote:
> > You are right. scsi_debug's pseudo-bus works.
> >
> > But probabaly, scsi_debug doesn't need to call
> > blk_queue_max_segment_size now.
>
> Either way works for me. :)
>
>
> >> Maybe dev_set_max_seg() is a better name, if people get really picky (I
> >> don't care).
> >
> > How about dma_set_max_seg_size()?
> >
> >
> > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> > index a417a6f..7adadfb 100644
> > --- a/drivers/scsi/scsi_lib.c
> > +++ b/drivers/scsi/scsi_lib.c
> > @@ -1554,6 +1554,7 @@ 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)
> > @@ -1565,6 +1566,9 @@ 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);
> >
> > + if (dev->max_segment_size)
> > + blk_queue_max_segment_size(q, dev->max_segment_size);
> > +
> > if (!shost->use_clustering)
> > clear_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
> > return q;
> > diff --git a/include/linux/device.h b/include/linux/device.h
> > index 3a38d1f..8046b60 100644
> > --- a/include/linux/device.h
> > +++ b/include/linux/device.h
> > @@ -443,6 +443,13 @@ struct device {
> >
> > struct dma_coherent_mem *dma_mem; /* internal for coherent mem
> > override */
> > +
> > + /*
> > + * a low level driver may set these to teach IOMMU code about
> > + * sg limitations.
> > + */
> > + unsigned int max_segment_size;
> > +
> > /* arch specific additions */
> > struct dev_archdata archdata;
> >
> > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> > index 2dc21cb..30404b8 100644
> > --- a/include/linux/dma-mapping.h
> > +++ b/include/linux/dma-mapping.h
> > @@ -31,6 +31,11 @@ static inline int valid_dma_direction(int dma_direction)
> > (dma_direction == DMA_FROM_DEVICE));
> > }
> >
> > +static inline void dma_set_max_seg_size(struct device *dev, unsigned int size)
> > +{
> > + dev->max_segment_size = size;
> > +}
> > +
>
> Definitely moving in the right direction, IMO. I would suggest a few
> minor changes to dma_set_max_seg_size(), to permit platforms to override
> the default behavior, and to get people into the habit of checking the
> return value (since it might matter in the future):
>
> 1) surround with #ifndef ARCH_HAS_DMA_MAX_SEG
>
> 2) change return value to 'int'
>
> 3) unconditionally return zero, for now.
>
> Otherwise, approach and code look good to me.
I will, thanks!
I'll post an updated patchset for -mm kernel soon.
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