Re: [PATCH 06/15] libata: Stop using host->max_cmd_len

[Brian King <brking@us.ibm.com>]

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Jeff Garzik wrote:
> Brian King wrote:
>> In preparation for SAS attached SATA devices, quit using
>> the max_cmd_len in the scsi_host struct.
>>
>> Signed-off-by: Brian King <brking@us.ibm.com>
> 
> I see this as a bit of a hack.  In general, its best to inform upper 
> layers of known limits as soon as possible.  For the non-SAS case, for 
> that point of view, this patch is a regression.
> 
> 	Jeff

Is the patch below ok? Then I'll add the cdb_len checking in the SAS
unique queuecommand entry point. This would still be a hack, but it wouldn't
be a regression for the non-SAS case. The other option I see would be to
add a max_cmd_len to the scsi_device which scsi core would check.

-- 
Brian King
eServer Storage I/O
IBM Linux Technology Center

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In preparation for SAS attached SATA devices, which will
not have a libata scsi_host, only setup host->max_cmd_len
if ap->host exists.

Signed-off-by: Brian King <brking@us.ibm.com>
---

 libata-dev-bjking1/drivers/scsi/libata-core.c |   12 +++++++-----
 1 files changed, 7 insertions(+), 5 deletions(-)

diff -puN drivers/scsi/libata-core.c~libata_cdb_len drivers/scsi/libata-core.c
--- libata-dev/drivers/scsi/libata-core.c~libata_cdb_len	2006-03-22 11:25:25.000000000 -0600
+++ libata-dev-bjking1/drivers/scsi/libata-core.c	2006-03-22 11:25:25.000000000 -0600
@@ -1301,11 +1301,13 @@ static int ata_dev_configure(struct ata_
 			       ap->id, dev->devno, ata_mode_string(xfer_mask));
 	}
 
-	ap->host->max_cmd_len = 0;
-	for (i = 0; i < ATA_MAX_DEVICES; i++)
-		ap->host->max_cmd_len = max_t(unsigned int,
-					      ap->host->max_cmd_len,
-					      ap->device[i].cdb_len);
+	if (ap->host) {
+		ap->host->max_cmd_len = 0;
+		for (i = 0; i < ATA_MAX_DEVICES; i++)
+			ap->host->max_cmd_len = max_t(unsigned int,
+						      ap->host->max_cmd_len,
+						      ap->device[i].cdb_len);
+	}
 
 	/* limit bridge transfers to udma5, 200 sectors */
 	if (ata_dev_knobble(ap, dev)) {
_