Need at least a <blk_device> argument.

Usage: scsi_ch_swp [-h] [-s 0|1] [-v] [-w] <blk_device>
  where:
    -h, --help           print usage message
    -s 0|1, --set 0|1    where:
                           0  - clear SWP and set RW mode
                           1  - set SWP and set RO mode
                                (default: read SWP and get RO flag)
    -v, --verbose        more verbose, show commands invoked
    -w, --wr             access <blk_device> read-write when '-s 0'
                         (default: access read-only in this case)

Access the Software Write Protect (SWP) bit in the SCSI control
mode page and if changed adjust the Linux block device (e.g.
/dev/sdc) settings accordingly. If supported, when the SWP bit
is set (1) the device is read-only; when clear (0) the device
is read-write (i.e. its contents can be read and changed).
When no options given it reads SWP and gets blockdev's RO flag.