Because part 14 is awfully loose in its definitions. Not only can commands
be arbitrarily extended with vendor blocks, but vendors have also interpreted
part 14 differently. Often there are different sets of exceptions for a
single vendor; it can be challenging enough to maintain a single driver for
one vendor's products, let alone for multiple vendors, even using reasonable
software abstraction techniques.
Most people who have sat down to write a SCSI II scanner driver have looked
at this idea (or something similar), but no one has managed to come up with
an abstraction that works for everyone.
Feel free to work on it, and if you can do better than everyone else so far,
great! However, you asked why we don't have it, and there's the reason...
michaelkjohnson
"Magazines all too frequently lead to books and should be regarded by the
prudent as the heavy petting of literature." -- Fran Lebowitz
Linux Application Development http://www.redhat.com/~johnsonm/lad/
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