The
com driver provides support for NS8250-, NS16450-, and NS16550-based EIA RS-232C (CCITT V.28) communications interfaces. The NS8250 and NS16450 have single character buffers, and the NS16550 has a 16 character buffer.
Input and output for each line may set to one of following baud rates; 50, 75, 110, 134.5, 150, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 38400, 57600, or 115200, or any other baud rate which is a factor of 115200.
The ttyXX devices are traditional dial-in devices; the dtyXX devices are used for dial-out. (See
tty(4).)
options COM_HAYESP adds support for the Hayes ESP serial board.
With
options RND_COM enabled, the
com driver can be used to collect entropy for the
rnd(4) entropy pool. The entropy is generated from interrupt randomness.
Arm32 specific
If “flags 1” is specified, the com driver will not set the MCR_IENABLE bit on the UART. This is mainly for use on AST multiport boards, where the MCR_IENABLE bit is used to control whether or not the devices use a shared interrupt.