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.
Jeff
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