A-Team_Digital_Solutions/android_kernel_motorola_sm6375
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[SCSI] relax scsi dma alignment

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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.

The reason for doing this is so that we don't get such a huge amount of
copy overhead in bio_copy_user() for udev.  (basically all inquiries it
issues can now be directly mapped).

Acked-by: Alan Stern <[email protected]>
Signed-off-by: James Bottomley <[email protected]>
This commit is contained in:
James Bottomley 2008-01-01 10:00:10 -06:00
commit 465ff3185e
5 changed files with 34 additions and 11 deletions
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6
drivers/ieee1394/sbp2.c
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@ -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;