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Message-ID: <874800.41815.qm@web31807.mail.mud.yahoo.com>
Date: Sun, 5 Dec 2010 12:53:50 -0800 (PST)
From: Luben Tuikov <ltuikov@yahoo.com>
Reply-To: ltuikov@yahoo.com
Subject: Re: [PATCH repost 3] [SCSI] Retrieve the Caching mode page
To: James Bottomley <James.Bottomley@suse.de>
Cc: Matthew Dharm <mdharm-kernel@one-eyed-alien.net>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org,
        linux-usb@vger.kernel.org, Greg KH <greg@kroah.com>
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--- On Wed, 11/24/10, Luben Tuikov <ltuikov@yahoo.com> wrote:
> 
> CBI/BBB isn't supposed to be, nor is designed to support
> SAM-modern devices. So while REQUEST LUN /may/ work on some
> devices which implement it in their firmware, it is NOT a
> requirement for those devices as they are not required to
> adhere to any SAM version. Those transport protocols define
> a class-specific request to get the maximum LUN, and another
> to reset the target port (instead of I_T Reset or LU Reset).
> They also do not support SCSI Status completion of the
> command, nor Autosense. They also do not provide TMFs. They
> provide none of the SCSI transport protocol services in
> support of the Execute Command procedure call. The SCSI
> layer shouldn't be trying to guess their "SCSI version", and
> or treat them as real SCSI devices sending REPORT LUNs, etc.
> commands.
> 
> Newer, modern transport protocols over USB, are part of
> SAM, and it is devices who connect via those protocols that
> are being disadvantaged, due to the adoption (assumption) of
> CBI/BBB well into the SCSI layer.
> 
> To this effect, the transport protocol can tell upper
> layers if the device is true SCSI (new usb transports or
> other) or hybrid (usb-storage). In the former case, the
> device is a SCSI device, in the latter, only basic commands
> should be attempted.
> 
> This isn't to say that firmware for those devices wouldn't
> be buggy. Of course it will, and most will probably port
> their legacy FW over to the new SPTL, but the protocol
> requirements are there by design (i.e. there is no longer
> Get Max Lun class-specific request, the application client
> has to send REPORT LUNS, and FW has to answer it) and we
> have to accommodate that.
> 
> It is in this spirit that this patch doesn't change wire
> behavior, but simply parses data returned by a command
> already supported by older protocols.

Did anyone pick up this patch?

    Luben

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