From: Jeff Garzik <jeff@garzik.org>
To: Tejun Heo <htejun@gmail.com>
Cc: "zhao, forrest" <forrest.zhao@intel.com>,
liml@rtr.ca, linux-ide@vger.kernel.org
Subject: Re: [PATCH] Snoop SET FEATURES - WRITE CACHE ENABLE/DISABLE command
Date: Mon, 29 May 2006 05:20:16 -0400 [thread overview]
Message-ID: <447ABCD0.2060305@garzik.org> (raw)
In-Reply-To: <447AB9FB.6020706@gmail.com>
Tejun Heo wrote:
> Jeff Garzik wrote:
>> 4) Using [__]scsi_add_device() is a regression from using
>> scsi_scan_target()
>
> I think it's taken from the hotplug patch store-attached-SCSI-device[1].
> Using [__]scsi_add_device() seems to be the only way to reliably obtain
> the attached sdev.
We want to continue to use scsi_scan_target(), because that's the
preferred model. In SCSI-land, the target is what receives RPC calls
(ATA commands, for us), which are then dispatched internally to one of
$N logical units (LU) according to the logical unit number (LUN).
In libata, of course, there is only one logical unit attached to the
target, LUN 0.
Regardless, using [__]scsi_add_device() is a regression, because libata
handles the transport layer completely -- and importantly -- handles all
addressing. scsi_add_device() is specifically for H/C/I/L, i.e. SPI
(parallel SCSI) addressing.
Eventually SCSI will reach a point where HCIL is not the only addressing
method. SAS disks, for example, are addressed via a LUN's WWN. SCSI
fibre channel addresses LUNs via WWN as well. Once SCSI core does not
exclusively use HCIL addressing, libata will reap the benefits of using
the proper scsi_target model.
Jeff
next prev parent reply other threads:[~2006-05-29 9:20 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-05-25 9:02 [PATCH] Snoop SET FEATURES - WRITE CACHE ENABLE/DISABLE command zhao, forrest
2006-05-27 0:15 ` Jeff Garzik
2006-05-29 6:35 ` zhao, forrest
2006-05-29 11:29 ` Mark Lord
2006-05-29 9:08 ` Tejun Heo
2006-05-29 9:18 ` zhao, forrest
2006-05-29 9:46 ` Tejun Heo
2006-05-29 9:20 ` Jeff Garzik [this message]
2006-05-29 9:43 ` Tejun Heo
2006-05-30 3:57 ` Jeff Garzik
2006-05-30 4:41 ` Jeff Garzik
2006-05-30 4:50 ` Tejun Heo
2006-05-30 4:57 ` Jeff Garzik
2006-05-30 5:10 ` Tejun Heo
2006-05-30 5:08 ` zhao, forrest
2006-05-30 7:22 ` Tejun Heo
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