scsi: check that busses support the DMA API before setting dma parameters

We'll start throwing warnings soon when dma_set_seg_boundary and
dma_set_max_seg_size are called on devices for buses that don't fully
support the DMA API.  Prepare for that by making the calls in the SCSI
midlayer conditional.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 3958a6d14bf457eb2acef5576d02c64c7d3972bc..7f0394c44920334b7ff963930d91a3d12e2f9613 100644 (file)
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1988,8 +1988,15 @@ void scsi_init_limits(struct Scsi_Host *shost, struct queue_limits *lim)
        if (shost->no_highmem)
                lim->features |= BLK_FEAT_BOUNCE_HIGH;
 
-       dma_set_seg_boundary(dev, shost->dma_boundary);
-       dma_set_max_seg_size(dev, shost->max_segment_size);
+       /*
+        * Propagate the DMA formation properties to the dma-mapping layer as
+        * a courtesy service to the LLDDs.  This needs to check that the buses
+        * actually support the DMA API first, though.
+        */
+       if (dev->dma_parms) {
+               dma_set_seg_boundary(dev, shost->dma_boundary);
+               dma_set_max_seg_size(dev, shost->max_segment_size);
+       }
 }
 EXPORT_SYMBOL_GPL(scsi_init_limits);