Re: [PATCH repost 3] [SCSI] Retrieve the Caching mode page

Luben Tuikov
2010-12-05T20:53:52Z

--- 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