Re: PATCH: exclude certain commands from emulated SCSI hosts

[Matthew Dharm <mdharm-scsi@one-eyed-alien.net>]

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On Sat, Apr 05, 2003 at 02:08:29PM -0600, James Bottomley wrote:
> On Sat, 2003-04-05 at 13:55, Matthew Dharm wrote:
> > 
> > My big complaint about that is that it's ugly.  I would like to keep the
> > device type as part of the filter command structure, so I can keep the call
> > to scsi_filter_cmd() simple and easy to maintain.  Maybe it's just me, but
> > I think that editing the filter table with an extra field will be easier to
> > get right than trying to maintain several different filter tables (for each
> > device type).
> 
> But that would reduce the power of the filter.  At the moment you can
> code "all devices apart from tapes" or "only disk and cdrom".  If I add
> it to the body of the filter, I either have to add a complex language to
> express this or reduce the power.  Neither seems to be particularly
> optimal

Okay, I'll buy that.

> > I guess the real power of this filter is in the ability to add logic to
> > scsi_filter_exceptions()... but centralizing that seems contrary to the
> > idea of doing this on a per-HBA basis.
> 
> The filter is just a language.  HBAs don't need to use all the
> expressions in the exceptions, so unless it gets too big I don't see why
> necessary additions can't go centrally.

Eh.  I'm not really convinced on this point (based on my past history of
trying to get patches into the SCSI subsystem), but I think that situation
is improving, so I'll just let it go.

Matt

-- 
Matthew Dharm                              Home: mdharm-usb@one-eyed-alien.net 
Maintainer, Linux USB Mass Storage Driver

God, root, what is difference?
					-- Pitr
User Friendly, 11/11/1999

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