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authorAlan Stern <stern@rowland.harvard.edu>2008-03-27 14:52:57 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2008-04-24 21:16:46 -0700
commit148d9fe4c91a6356dae1b05b76b8133586c26be4 (patch)
tree46156fcacfb5a402c9f222a06257b3926ff17497
parentcc901bbb2e2a4e4f96da3d70dae332882c10054b (diff)
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>
-rw-r--r--drivers/usb/storage/scsiglue.c14
1 files changed, 8 insertions, 6 deletions
diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index 5405ba8cd9d..521f0297aef 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -73,6 +73,7 @@ static const char* host_info(struct Scsi_Host *host)
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 @@ static int slave_alloc (struct scsi_device *sdev)
/* 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