illumos gate

When trying to create an action in libscsi, which is effectively a command to run, it needs to know how to determine the size of that command. One of the challenges with this is that if libscsi doesn't know the command, which is often common of vendor specific commands, then it will fail. We need to add a new interface to allow someone to specify the size of the cdb.

This is further complicated by the uscsi engine in libscsi, which needs to know how to determine the cdb size. Today it does that by trying to determine that from the command. However, that has no relation to the actual allocated size. If a user changes the first byte in the cdb, this could lead to us potentially giving a larger or smaller size in that command. While it might be more accurate for uscsi to try and determine it, it wouldn't be more correct necessarily. Really, the expected contract is that the command shouldn't change once it's been allocated.

I tested this with a custom program that leverages the new library. I also tested some existing consumers ala fwflash to make sure that they're not impacted.