USB: usb-storage: use adaptive DMA mask
This patch (as1060) makes usb-storage set the DMA alignment mask for
SCSI slaves to match the maxpacket size of the bulk-IN endpoint,
rather than always setting it to 511. For full-speed devices that
mask is too restrictive, and wireless USB devices can have maxpacket
sizes larger than 512.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index 5405ba8..521f029 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -73,6 +73,7 @@
static int slave_alloc (struct scsi_device *sdev)
{
struct us_data *us = host_to_us(sdev->host);
+ struct usb_host_endpoint *bulk_in_ep;
/*
* Set the INQUIRY transfer length to 36. We don't use any of
@@ -84,12 +85,13 @@
/* Scatter-gather buffers (all but the last) must have a length
* divisible by the bulk maxpacket size. Otherwise a data packet
* would end up being short, causing a premature end to the data
- * transfer. Since high-speed bulk pipes have a maxpacket size
- * of 512, we'll use that as the scsi device queue's DMA alignment
- * mask. Guaranteeing proper alignment of the first buffer will
- * have the desired effect because, except at the beginning and
- * the end, scatter-gather buffers follow page boundaries. */
- blk_queue_update_dma_alignment(sdev->request_queue, (512 - 1));
+ * transfer. We'll use the maxpacket value of the bulk-IN pipe
+ * to set the SCSI device queue's DMA alignment mask.
+ */
+ bulk_in_ep = us->pusb_dev->ep_in[usb_pipeendpoint(us->recv_bulk_pipe)];
+ blk_queue_update_dma_alignment(sdev->request_queue,
+ le16_to_cpu(bulk_in_ep->desc.wMaxPacketSize) - 1);
+ /* wMaxPacketSize must be a power of 2 */
/*
* The UFI spec treates the Peripheral Qualifier bits in an