[7191] in linux-scsi channel archive
Re: Fixing SCSI Layer
daemon@ATHENA.MIT.EDU (Mark Veteikis)
Wed Sep 8 18:21:23 1999
From: Mark Veteikis <mark@iphase.com>
To: alan@lxorguk.ukuu.org.uk (Alan Cox)
Date: Wed, 8 Sep 1999 17:19:23 -0500 (CDT)
Cc: groudier@club-internet.fr, mark@iphase.com,
linux-scsi@vger.rutgers.edu
In-Reply-To: <E11OpVt-0002lm-00@the-village.bc.nu> from "Alan Cox" at Sep 8, 99 10:44:20 pm
>
> > This flaw in Linux-SCSI requires driver to be able to handle any transfer
> > direction required by a device for a command. Usually, the direction is
> > enforced only for common opcodes as READ*/WRITE* and friends. For non
> > usual commands the driver/controller pair must wait the first data phase
> > asked by the device to know about the transfer direction.
>
> Many drivers cant wait for the phase to decide. They have to use tables or
> be told
Yes, exactly the reason I suggested the putting help about direction be put
in the Scsi_Cmnd structure. I went through my SCSI-II spec. looking
for opcodes that transfer direction was not easily identifiable and
it does look like vendor-specific commands are the exception.
Perhaps, the transfer direction "hint" placed in Scsi_Cmnd could provide
a suggested transfer direction such as, data out, data in, bidirectional,
or "vendor-specific/direction not known".
--
Mark Veteikis mark@iphase.com 1-214-654-5257
Interphase Corp. 13800 Senlac Dallas Tx. 75234
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