scsi_xpt: save the device specific field of the mode parameters header
Save the device specific field of the mode parameters header while
querying Control extension page during PROBE_MODE_SENSE stage.
Allow access to the saved value via a new XPT_DEV_ADVINFO sub-type.
Consider saving more of the header or, perhaps, both the whole header
and the page.
geom_disk: deny opening disk for writing if it's marked as write-protected
A new disk(9) flag is added to mark write protected disks.
Another alternative would be to add another parameter to d_open, so
that the open mode could be passed to it and the disk drivers could
make the decision internally.
scsi_da: set write-protected flag based on mode paramter header
Check if the disk is write protected using bit 7 of the device specific
field in the mode parameter header returned by MODE SENSE and saved by
Consider if we also need / want to check SWP bit (SCP_SWP) in the
Control mode page (0x0A) that we query at PROBE_MODE_SENSE stage.