[PATCH] queue dma alignment

Make it possible for a device to specify the dma alignment restrictions
it has. This will be used by future infrastructure when mapping in user
pages, and allows us to dma to on ATAPI even though user address and
length is not sector size aligned.

drivers/block/ll_rw_blk.c

@@ -242,6 +242,7 @@ void blk_queue_make_request(request_queue_t * q, make_request_fn * mfn)
 	q->backing_dev_info.state = 0;
 	blk_queue_max_sectors(q, MAX_SECTORS);
 	blk_queue_hardsect_size(q, 512);
+	blk_queue_dma_alignment(q, 511);
 
 	/*
 	 * by default assume old behaviour and bounce for any highmem page
@@ -408,6 +409,21 @@ void blk_queue_segment_boundary(request_queue_t *q, unsigned long mask)
 	q->seg_boundary_mask = mask;
 }
 
+/**
+ * blk_queue_dma_alignment - set dma length and memory alignment
+ * @q:  the request queue for the device
+ * @dma_mask:  alignment mask
+ *
+ * description:
+ *    set required memory and length aligment for direct dma transactions.
+ *    this is used when buiding direct io requests for the queue.
+ *
+ **/
+void blk_queue_dma_alignment(request_queue_t *q, int mask)
+{
+	q->dma_alignment = mask;
+}
+
 void blk_queue_assign_lock(request_queue_t *q, spinlock_t *lock)
 {
 	spin_lock_init(lock);
@@ -2124,6 +2140,7 @@ EXPORT_SYMBOL(blk_queue_max_hw_segments);
 EXPORT_SYMBOL(blk_queue_max_segment_size);
 EXPORT_SYMBOL(blk_queue_hardsect_size);
 EXPORT_SYMBOL(blk_queue_segment_boundary);
+EXPORT_SYMBOL(blk_queue_dma_alignment);
 EXPORT_SYMBOL(blk_rq_map_sg);
 EXPORT_SYMBOL(blk_nohighio);
 EXPORT_SYMBOL(blk_dump_rq_flags);

include/linux/blkdev.h

@@ -215,6 +215,7 @@ struct request_queue
 	unsigned int		max_segment_size;
 
 	unsigned long		seg_boundary_mask;
+	unsigned int		dma_alignment;
 
 	wait_queue_head_t	queue_wait;
 
@@ -346,6 +347,7 @@ extern void blk_queue_segment_boundary(request_queue_t *, unsigned long);
 extern void blk_queue_assign_lock(request_queue_t *, spinlock_t *);
 extern void blk_queue_prep_rq(request_queue_t *, prep_rq_fn *pfn);
 extern void blk_queue_merge_bvec(request_queue_t *, merge_bvec_fn *);
+extern void blk_queue_dma_alignment(request_queue_t *, int);
 extern struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev);
 
 extern int blk_rq_map_sg(request_queue_t *, struct request *, struct scatterlist *);
@@ -392,6 +394,21 @@ static inline int bdev_hardsect_size(struct block_device *bdev)
 	return queue_hardsect_size(bdev_get_queue(bdev));
 }
 
+static inline int queue_dma_alignment(request_queue_t *q)
+{
+	int retval = 511;
+
+	if (q && q->dma_alignment)
+		retval = q->dma_alignment;
+
+	return retval;
+}
+
+static inline int bdev_dma_aligment(struct block_device *bdev)
+{
+	return queue_dma_alignment(bdev_get_queue(bdev));
+}
+
 #define blk_finished_io(nsects)	do { } while (0)
 #define blk_started_io(nsects)	do { } while (0)