On Mon, Jun 29, 2009 at 07:34:31AM -0600, Matthew Wilcox wrote:
> SCSI commands come in different sizes. Drivers are assumed to support
> commands up to 12 bytes long, unless they report otherwise by setting
> their max_cmd_len parameter. Unfortunately, the command that reports
> the device capacity for devices over 2TB is a 16 byte command, and the
> aic7xxx driver doesn't claim it supports 16 byte commands, so we refuse
> to even send it to the driver.
>
> It's possible the aic7xxx hardware does support 16 byte commands. If so,
> this is an easy fix. If it doesn't, you could try replacing the card
> with one that does (for example, the LSI 8xx and 10xx cards all support
> 16 byte commands).
>
> You could also go for a configuration fix where you reconfigure the array
> with LUNs below 2TB and then use MD or DM to stitch them back together
> into a single device.
>
> Let's hope someone who understands the aic7xxx hardware can tell us
> whether it supports 16 byte commands or not.
I should have read the driver more thoroughly before writing that email.
It seems the driver does support larger commands. Here's the hint:
hscb->cdb_len = cmd->cmd_len;
if (hscb->cdb_len <= 12) {
memcpy(hscb->shared_data.cdb, cmd->cmnd, hscb->cdb_len);
} else {
memcpy(hscb->cdb32, cmd->cmnd, hscb->cdb_len);
scb->flags |= SCB_CDB32_PTR;
}
The aic79xx is a little more tricky ... it seems it has different cases to
support 12, 16 and >16 byte CDBs, but it's not clear that the >16 byte CDB case is implemented. Let's be conservative for now and bump it up to 16 bytes instead of 32.
diff --git a/drivers/scsi/aic7xxx/aic79xx_osm.c b/drivers/scsi/aic7xxx/aic79xx_osm.c
index 75b2331..3853f33 100644
--- a/drivers/scsi/aic7xxx/aic79xx_osm.c
+++ b/drivers/scsi/aic7xxx/aic79xx_osm.c
@@ -1241,6 +1241,7 @@ ahd_linux_register_host(struct ahd_softc *ahd, struct scsi_host_template *templa
host->max_lun = AHD_NUM_LUNS;
host->max_channel = 0;
host->sg_tablesize = AHD_NSEG;
+ host->max_cmd_len = 16;
ahd_lock(ahd, &s);
ahd_set_unit(ahd, ahd_linux_unit++);
ahd_unlock(ahd, &s);
diff --git a/drivers/scsi/aic7xxx/aic7xxx_osm.c b/drivers/scsi/aic7xxx/aic7xxx_osm.c
index fd2b978..2d069de 100644
--- a/drivers/scsi/aic7xxx/aic7xxx_osm.c
+++ b/drivers/scsi/aic7xxx/aic7xxx_osm.c
@@ -1115,6 +1115,7 @@ ahc_linux_register_host(struct ahc_softc *ahc, struct scsi_host_template *templa
host->max_lun = AHC_NUM_LUNS;
host->max_channel = (ahc->features & AHC_TWIN) ? 1 : 0;
host->sg_tablesize = AHC_NSEG;
+ host->max_cmd_len = 32;
ahc_lock(ahc, &s);
ahc_set_unit(ahc, ahc_linux_unit++);
ahc_unlock(ahc, &s);
--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."
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