On Mon, 2007-12-31 at 17:57 -0500, Alan Stern wrote:
> On Mon, 31 Dec 2007, James Bottomley wrote:
> > --- a/drivers/usb/storage/scsiglue.c
> > +++ b/drivers/usb/storage/scsiglue.c
> > @@ -82,6 +82,12 @@ static int slave_alloc (struct scsi_device *sdev)
> > sdev->inquiry_len = 36;
> >
> > /*
> > + * Update the dma alignment (minimum alignment requirements for
> > + * start and end of DMA transfers) to be a sector
> > + */
> > + blk_queue_update_dma_alignment(sdev->request_queue, 511);
> > +
> > + /*
> > * The UFI spec treates the Peripheral Qualifier bits in an
> > * INQUIRY result as reserved and requires devices to set them
> > * to 0. However the SCSI spec requires these bits to be set
>
> It would be better to move the existing code from the start of
> slave_configure() up into slave_alloc(). Otherwise it's fine.
Um, yes, you're right, I didn't notice there was an existing one ... I
just assumed you were relying on the SCSI default.
Here's an updated patch.
James
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index fed5308..25c9470 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -824,6 +824,9 @@ static void ata_scsi_sdev_config(struct scsi_device *sdev)
* requests.
*/
sdev->max_device_blocked = 1;
+
+ /* set the min alignment */
+ blk_queue_update_dma_alignment(sdev->request_queue, ATA_DMA_PAD_MASK);
}
static void ata_scsi_dev_config(struct scsi_device *sdev,
@@ -868,7 +871,7 @@ int ata_scsi_slave_config(struct scsi_device *sdev)
if (dev)
ata_scsi_dev_config(sdev, dev);
- return 0; /* scsi layer doesn't check return value, sigh */
+ return 0;
}
/**
diff --git a/drivers/firewire/fw-sbp2.c b/drivers/firewire/fw-sbp2.c
index 624ff3e..c2169d2 100644
--- a/drivers/firewire/fw-sbp2.c
+++ b/drivers/firewire/fw-sbp2.c
@@ -1238,6 +1238,12 @@ static int sbp2_scsi_slave_alloc(struct scsi_device
*sdev)
sdev->allow_restart = 1;
+ /*
+ * Update the dma alignment (minimum alignment requirements for
+ * start and end of DMA transfers) to be a sector
+ */
+ blk_queue_update_dma_alignment(sdev->request_queue, 511);
+
if (lu->tgt->workarounds & SBP2_WORKAROUND_INQUIRY_36)
sdev->inquiry_len = 36;
diff --git a/drivers/ieee1394/sbp2.c b/drivers/ieee1394/sbp2.c
index b83d254..1eda11a 100644
--- a/drivers/ieee1394/sbp2.c
+++ b/drivers/ieee1394/sbp2.c
@@ -1963,6 +1963,12 @@ static int sbp2scsi_slave_alloc(struct scsi_device *sdev)
lu->sdev = sdev;
sdev->allow_restart = 1;
+ /*
+ * Update the dma alignment (minimum alignment requirements for
+ * start and end of DMA transfers) to be a sector
+ */
+ blk_queue_update_dma_alignment(sdev->request_queue, 511);
+
if (lu->workarounds & SBP2_WORKAROUND_INQUIRY_36)
sdev->inquiry_len = 36;
return 0;
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index d1a4671..0aa5296 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1667,6 +1667,14 @@ struct request_queue *__scsi_alloc_queue(struct
Scsi_Host *shost,
if (!shost->use_clustering)
clear_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
+
+ /*
+ * set a reasonable default alignment on word boundaries: the
+ * host and device may alter it using
+ * blk_queue_update_dma_alignment() later.
+ */
+ blk_queue_dma_alignment(q, 0x03);
+
return q;
}
EXPORT_SYMBOL(__scsi_alloc_queue);
diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index 7c9593b..dd8b13e 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -81,6 +81,16 @@ static int slave_alloc (struct scsi_device *sdev)
*/
sdev->inquiry_len = 36;
+ /* 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));
+
/*
* The UFI spec treates the Peripheral Qualifier bits in an
* INQUIRY result as reserved and requires devices to set them
@@ -100,16 +110,6 @@ static int slave_configure(struct scsi_device *sdev)
{
struct us_data *us = host_to_us(sdev->host);
- /* 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_dma_alignment(sdev->request_queue, (512 - 1));
-
/* Many devices have trouble transfering more than 32KB at a time,
* while others have trouble with more than 64K. At this time we
* are limiting both to 32K (64 sectores).
-
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