On May 18 Clemens Ladisch wrote at linux1394-devel: > The SBP-2/3 specifications do not require any alignment of data > buffers; only their own data structures need to be quadlet-aligned. SBP-2 clause 3.1.2.24 requires that system memory accepts quadlet r/w access. Memory which is not aligned at quadlet boundaries is not accessible by quadlet accesses per IEEE 1394 clause 6.2.5.2.2. > This patch is perfectly safe because there is no actual change: > the SCSI framework uses a default block queue DMA alignment of > 32 bits anyway. This code was added after recommendation to set it explicitly in the driver: http://marc.info/?l=linux-scsi&m=120137366708017 http://thread.gmane.org/gmane.linux.kernel.firewire.devel/11424 It is probably not going to happen that somebody decreases the SCSI default. But perhaps we should still keep this explicit...? > Signed-off-by: Clemens Ladisch <clemens@xxxxxxxxxx> > --- > drivers/firewire/sbp2.c | 8 ++------ > 1 files changed, 2 insertions(+), 6 deletions(-) > > --- a/drivers/firewire/sbp2.c > +++ b/drivers/firewire/sbp2.c > @@ -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 > > @@ -1530,9 +1529,6 @@ static int sbp2_scsi_slave_alloc(struct scsi_device *sdev) > > sdev->allow_restart = 1; > > - /* 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/ -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
