[1/4] scsi: check that busses support the DMA API before setting dma parameters
Commit Message
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>
---
drivers/scsi/scsi_lib.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
Comments
On 24/08/2024 4:49 am, Christoph Hellwig wrote:
> 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.
Just thinking ahead, might it be worth a logical "are SG segment limits
relevant?" wrapper around the dev->dma_parms reference? Not a big deal
for now if we think this site is the only user, so either way,
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> drivers/scsi/scsi_lib.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 3958a6d14bf457..7f0394c4492033 100644
> --- 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);
>
@@ -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);