Commit 148d9fe4 authored by Alan Stern's avatar Alan Stern Committed by Greg Kroah-Hartman
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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: default avatarAlan Stern <>
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent cc901bbb
......@@ -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)];
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
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