1 files changed, 12 insertions, 14 deletions

diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index a73ea495d5a7..59190d88fa9f 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -65,6 +65,7 @@ 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);
+        int maxp;
 
         /*
          * Set the INQUIRY transfer length to 36.  We don't use any of
@@ -74,20 +75,17 @@ static int slave_alloc (struct scsi_device *sdev)
         sdev->inquiry_len = 36;
 
         /*
-         * USB has unusual DMA-alignment requirements: Although the
-         * starting address of each scatter-gather element doesn't matter,
-         * the length of each element except the last must be divisible
-         * by the Bulk maxpacket value.  There's currently no way to
-         * express this by block-layer constraints, so we'll cop out
-         * and simply require addresses to be aligned at 512-byte
-         * boundaries.  This is okay since most block I/O involves
-         * hardware sectors that are multiples of 512 bytes in length,
-         * and since host controllers up through USB 2.0 have maxpacket
-         * values no larger than 512.
-         *
-         * But it doesn't suffice for Wireless USB, where Bulk maxpacket
-         * values can be as large as 2048.  To make that work properly
-         * will require changes to the block layer.
+         * USB has unusual scatter-gather requirements: the length of each
+         * scatterlist element except the last must be divisible by the
+         * Bulk maxpacket value.  Fortunately this value is always a
+         * power of 2.  Inform the block layer about this requirement.
+         */
+        maxp = usb_maxpacket(us->pusb_dev, us->recv_bulk_pipe, 0);
+        blk_queue_virt_boundary(sdev->request_queue, maxp - 1);
+
+        /*
+         * Some host controllers may have alignment requirements.
+         * We'll play it safe by requiring 512-byte alignment always.
          */
         blk_queue_update_dma_alignment(sdev->request_queue, (512 - 1));