Add `TIOCM_OUT1`, `TIOCM_OUT2`, and `TIOCM_LOOP` constants to `termios`

[rruuaanng]

Feature or enhancement

Proposal:

This issue suggests adding new termios constants.

TIOCM_LOOP

example:

int fd = /* /dev/ttyS0 */
int status = /* modulator status */
status |= TIOCM_LOOP;

ioctl(fd, TIOCMSET, &status);
/* subsequent 'write()' will send data to 'fd' instead of the remote terminal device */

It's used to enable the serial port loopback mode, that is, the local tx will send messages to the local rx instead of the external device

TIOCM_OUT1
TIOCM_OUT2

It's suitable for the physical characteristics of the terminal equipment, such as interrupt and chip select output

for example, a library like this uses.

https://github.com/makerbot/pyserial

ref: https://github.com/torvalds/linux/blob/master/include/uapi/asm-generic/termios.h

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-127336

[erlend-aasland]

This issue suggests adding new termios constants.

Which constants? What do they do? Why are you proposing to add these flags? Always explain proposed changes in detail.