The block driver uses scatter-gather lists with sg[0] being the
request information (struct virtio_blk_outhdr) with the type, sector
and inbuf id. The next N sg entries are the bio itself, then the last
sg is the status byte. Whether the N entries are in or out depends on
whether it's a read or a write.
We accept the normal (SCSI) ioctls: they get handed through to the other
side which can then handle it or reply that it's unsupported. It's
not clear that this actually works in general, since I don't know
if blk_pc_request() requests have an accurate rq_data_dir().
Although we try to reply -ENOTTY on unsupported commands, ioctl(fd,
CDROMEJECT) returns success to userspace. This needs a separate
patch.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jens Axboe <jens.axboe@oracle.com>
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