SET_LINE_REQUEST_TYPE (0x21) expects a 7 byte buffer: 4 bytes for
speed, 1 byte of 0 for 1 stop bit, 1 byte of 0 for no parity, and
1 byte of 8 for 8 data bits. Under Raspbian at least, sending a
single byte only caused a broken pipe error and the soft_reboot
always failed.
SET_LINE_REQUEST_TYPE (0x21) expects a 7 byte buffer: 4 bytes for speed, 1 byte of 0 for 1 stop bit, 1 byte of 0 for no parity, and 1 byte of 8 for 8 data bits. Under Raspbian at least, sending a single byte only caused a broken pipe error and the soft_reboot always failed.