lkml.org 
[lkml]   [2001]   [Jun]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRE: question about scsi generic behavior
Date
Well, the problem is not with non-512byte block device. The problem is
if the device is 512 byte block-sized device and if you use sg_dd with
bs=1024 or bs=2048, then it fails. I can understand if this fails
on a sequential device. But this fails on a disk. To be specific,
the problem is this : in case of fibre channel, you can specify
the FCP_DL in addition to the transfer-length which goes into CDB.
Now, when e.g. we use the following command,

sg_dd if=/dev/zero of=/dev/sg5 bs=2048 count=1,

and if in the low-level driver, we set the FCP_DL to 2048 and
in the CDB portition of FCP_CMND if we set the transfer-length to 1,
then the drive may not honour the FCP_DL and just look at the
transfer-length
and send XFER_RDY for 512 byte data. Once the HBA transfers the 512 byte of
data, then drive will send FCP_STATUS with status=good. Well, if you
look at it, we want to transfer 2048 bytes of data to the device,
whereas the device completes the command with good status after
transferring only 512 bytes. I hope this is more clear.

I guess, probably the sg driver is probably not looking at the block
size information returned in response to READ_CAPACITY command.

Regards,
-hiren
(408)970-3062
hiren_mehta@agilent.com

> -----Original Message-----
> From: Alan Cox [mailto:alan@lxorguk.ukuu.org.uk]
> Sent: Friday, June 08, 2001 5:37 PM
> To: hiren_mehta@agilent.com
> Cc: chamb@almaden.ibm.com; linux-scsi@vger.kernel.org;
> linux-kernel@vger.kernel.org
> Subject: Re: question about scsi generic behavior
>
>
> > Hardcoding of block size to 512 bytes for disk devices is
> what currently
> > either the block device driver or the sd driver is doing.
> Because, if
>
> I'm using 2048 byte block sized scsi media just fine. I've
> not tried using
> sg on the same device
>
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 12:55    [W:0.022 / U:0.632 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site