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firewire: sbp2: document the absence of alignment requirements

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The SBP-2/3 specifications do not require any alignment of data
buffers; only their own data structures need to be quadlet-aligned
[SR: or octlet-aligned].

Fix the comments to reflect this, but leave the actual alignment at
32 bits to avoid theoretical problems with target implementations
that might handle this incorrectly.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
This commit is contained in:
Clemens Ladisch 2012-05-18 22:26:21 +02:00 committed by Stefan Richter
parent 935f672e02
commit 26c72e22c9
1 changed files with 6 additions and 4 deletions
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10
drivers/firewire/sbp2.c
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@ -207,9 +207,8 @@ static const struct device *lu_dev(const struct sbp2_logical_unit *lu)
#define SBP2_MAX_CDB_SIZE 16
/*
* The default maximum s/g segment size of a FireWire controller is
* usually 0x10000, but SBP-2 only allows 0xffff. Since buffers have to
* be quadlet-aligned, we set the length limit to 0xffff & ~3.
* The maximum SBP-2 data buffer size is 0xffff. We quadlet-align this
* for compatibility with earlier versions of this driver.
*/
#define SBP2_MAX_SEG_SIZE 0xfffc
@ -1530,7 +1529,10 @@ static int sbp2_scsi_slave_alloc(struct scsi_device *sdev)
sdev->allow_restart = 1;
/* SBP-2 requires quadlet alignment of the data buffers. */
/*
* SBP-2 does not require any alignment, but we set it anyway
* for compatibility with earlier versions of this driver.
*/
blk_queue_update_dma_alignment(sdev->request_queue, 4 - 1);
if (lu->tgt->workarounds & SBP2_WORKAROUND_INQUIRY_36)