SG_NEXT_CMD_LEN 0x2283. This ioctl() is not required with sg_io_hdr structure since command length
is set explicitly for every command.
Assumes 3rd argument is pointing to an int. The value of the int (if > 0)
will be used as the SCSI command length of the next SCSI command sent to
a write() using the sg_header interface. After that write() the SCSI
command length logic is reset to use automatic length detection (i.e.
depending on SCSI command group and the 'twelve_byte' field). If the
current SCSI command length maximum of 16 is exceeded then the affected
write() will yield an EDOM error. Giving this ioctl() a value of 0 will
set automatic length detection for the next write(). N.B. Only the following
write() on this fd is affected by this ioctl().