path: root/include/linux/blkdev.h
diff options
authorJames Bottomley <James.Bottomley@HansenPartnership.com>2008-01-10 11:30:36 -0600
committerJens Axboe <jens.axboe@oracle.com>2008-01-28 10:54:11 +0100
commitfa0ccd837e3dddb44c7db2f128a8bb7e4eabc21a (patch)
treeade071502f3e7cba423295890d828f0f301ad731 /include/linux/blkdev.h
parent__bio_clone: don't calculate hw/phys segment counts (diff)
block: implement drain buffers
These DMA drain buffer implementations in drivers are pretty horrible to do in terms of manipulating the scatterlist. Plus they're being done at least in drivers/ide and drivers/ata, so we now have code duplication. The one use case for this, as I understand it is AHCI controllers doing PIO mode to mmc devices but translating this to DMA at the controller level. So, what about adding a callback to the block layer that permits the adding of the drain buffer for the problem devices. The idea is that you'd do this in slave_configure after you find one of these devices. The beauty of doing it in the block layer is that it quietly adds the drain buffer to the end of the sg list, so it automatically gets mapped (and unmapped) without anything unusual having to be done to the scatterlist in driver/scsi or drivers/ata and without any alteration to the transfer length. Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to '')
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index c7a3ab575c24..e542c8fd9215 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -429,6 +429,8 @@ struct request_queue
unsigned int max_segment_size;
unsigned long seg_boundary_mask;
+ void *dma_drain_buffer;
+ unsigned int dma_drain_size;
unsigned int dma_alignment;
struct blk_queue_tag *queue_tags;
@@ -760,6 +762,8 @@ extern void blk_queue_max_hw_segments(struct request_queue *, unsigned short);
extern void blk_queue_max_segment_size(struct request_queue *, unsigned int);
extern void blk_queue_hardsect_size(struct request_queue *, unsigned short);
extern void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b);
+extern int blk_queue_dma_drain(struct request_queue *q, void *buf,
+ unsigned int size);
extern void blk_queue_segment_boundary(struct request_queue *, unsigned long);
extern void blk_queue_prep_rq(struct request_queue *, prep_rq_fn *pfn);
extern void blk_queue_merge_bvec(struct request_queue *, merge_bvec_fn *);