Well, I'm working on polishing up my virtual HBA for usb storage devices,
and I realized that it would be really nice to rely on the
sc_data_direction field to tell me which way the data transfer is going to
go.
For reference, I _have_ to get this information from somewhere. I have to
know ahead of time which way the data will flow to set up the USB
transaction properly.
Right now, I have my own little table of directions. Unfortunately, it
could be wrong in some places -- I can't really test it very well. So I
thought I'd just shift to using the sc_data_direction field.
Unfortunately, most applications don't set this bit yet. Any request
which originates from within the kernel will have it set correctly.
However, requests from userspace applications (such as cdparanoia) will
not have it set.
So, my choices are either to (a) stick with the unreliable but apparently
functional table, or (b) use the field and be prepared to reject commands
which don't have the field set.
But, as I was thinking about it, it occured to me that the only way we
would get people to being using this field in a widespread way would be to
make the SCSI layers enforce this -- that is, reject any commands issued
that didn't indicate the direction somehow.
Are there any plans to do this? Or are we going to continue to support
old applications on 2.4.0 which don't set this field? I realize that
there may be lots of applications which need updating, but it's a pretty
simple update to make and it does coincide nicely with a pretty big kernel
release (which is a time when developers should be going back to make sure
that their programs work with the new interface).
Matt Dharm
--
Matthew Dharm Home: [EMAIL PROTECTED]
Engineer, Qualcomm, Inc. Work: [EMAIL PROTECTED]
It was a new hope.
-- Dust Puppy
User Friendly, 12/25/1998
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