target: Refactor MODE SENSE emulation
Convert spc_emulate_modesense() to use a table of mode pages, rather
than a switch statement. This makes it possible to add more pages
sanely -- in particular we no longer need to make sure we keep the
0x3f (return all mode pages) case in sync.
While we're touching this code, make our MODE SENSE emulation a bit
better in a couple of ways:
- When the initiator passes PC == 1 asking for changeable values,
return all 0s to show we don't support setting anything.
- Return a block descriptor for disk devices.
(nab: fix up device attribute references to use dev->dev_attrib
in for-next code)
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>