on patch "[SCSI] relax scsi dma alignment"

on patch "[SCSI] relax scsi dma alignment"

[Stefan Richter]

On commit 465ff3185e0cb76d46137335a4d21d0d9d3ac8a2:
> This patch relaxes the default SCSI DMA alignment from 512 bytes to 4
> bytes.  I remember from previous discussions that usb and firewire have
> sector size alignment requirements, so I upped their alignments in the
> respective slave allocs.
[...]
>  drivers/ata/libata-scsi.c      |    5 ++++-
>  drivers/firewire/fw-sbp2.c     |    6 ++++++
>  drivers/ieee1394/sbp2.c        |    6 ++++++
>  drivers/scsi/scsi_lib.c        |    8 ++++++++
>  drivers/usb/storage/scsiglue.c |   20 ++++++++++----------
>  5 files changed, 34 insertions(+), 11 deletions(-)

No, FireWire only requires 4 bytes alignment.

I will channel a reversion of the firewire and ieee1394 hunks through
linux1394-2.6.git for 2.6.26.
-- 
Stefan Richter
-=====-==--- ---= ==-=-
http://arcgraph.de/sr/

Re: on patch "[SCSI] relax scsi dma alignment"

[James Bottomley]

On Sat, 2008-01-26 at 19:49 +0100, Stefan Richter wrote:
> On commit 465ff3185e0cb76d46137335a4d21d0d9d3ac8a2:
> > This patch relaxes the default SCSI DMA alignment from 512 bytes to 4
> > bytes.  I remember from previous discussions that usb and firewire have
> > sector size alignment requirements, so I upped their alignments in the
> > respective slave allocs.
> [...]
> >  drivers/ata/libata-scsi.c      |    5 ++++-
> >  drivers/firewire/fw-sbp2.c     |    6 ++++++
> >  drivers/ieee1394/sbp2.c        |    6 ++++++
> >  drivers/scsi/scsi_lib.c        |    8 ++++++++
> >  drivers/usb/storage/scsiglue.c |   20 ++++++++++----------
> >  5 files changed, 34 insertions(+), 11 deletions(-)
> 
> No, FireWire only requires 4 bytes alignment.
> 
> I will channel a reversion of the firewire and ieee1394 hunks through
> linux1394-2.6.git for 2.6.26.

Don't revert, just put the numbers down to 4 (just in case someone
decides to lower the default SCSI alignment down from four ...).

James

[PATCH 2.6.24-git3] firewire: fw-sbp2: relax SCSI DMA alignment

[Stefan Richter]

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
---

Not run-time tested yet.

 drivers/firewire/fw-sbp2.c |    7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

Index: linux-2.6.24-git3/drivers/firewire/fw-sbp2.c
===================================================================
--- linux-2.6.24-git3.orig/drivers/firewire/fw-sbp2.c
+++ linux-2.6.24-git3/drivers/firewire/fw-sbp2.c
@@ -1309,11 +1309,8 @@ static int sbp2_scsi_slave_alloc(struct 
 
 	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);
+	/* SBP-2 requires quadlet alignment of the data buffers. */
+	blk_queue_update_dma_alignment(sdev->request_queue, 4 - 1);
 
 	if (lu->tgt->workarounds & SBP2_WORKAROUND_INQUIRY_36)
 		sdev->inquiry_len = 36;

-- 
Stefan Richter
-=====-==--- ---= ==-==
http://arcgraph.de/sr/


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[PATCH 2.6.24-git3] ieee1394: sbp2: relax SCSI DMA alignment

[Stefan Richter]

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
---

Not run-time tested yet.

 drivers/ieee1394/sbp2.c |    7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

Index: linux-2.6.24-git3/drivers/ieee1394/sbp2.c
===================================================================
--- linux-2.6.24-git3.orig/drivers/ieee1394/sbp2.c
+++ linux-2.6.24-git3/drivers/ieee1394/sbp2.c
@@ -1966,11 +1966,8 @@ static int sbp2scsi_slave_alloc(struct s
 	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);
+	/* SBP-2 requires quadlet alignment of the data buffers. */
+	blk_queue_update_dma_alignment(sdev->request_queue, 4 - 1);
 
 	if (lu->workarounds & SBP2_WORKAROUND_INQUIRY_36)
 		sdev->inquiry_len = 36;

-- 
Stefan Richter
-=====-==--- ---= ==-==
http://arcgraph.de/sr/


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This SF.net email is sponsored by: Microsoft
Defy all challenges. Microsoft(R) Visual Studio 2008.
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