can not quit cmux mode, and there are ttys residue

[alex-founder]

when module reset , the UART will not quit and the ttyGSM is residue , so can not rebuild the new ttyGSM.
please help me and tell me how to quit cmux, thank you

[eric-bentley]

I put cleanup code in the signal_handler to send the terminate packet. Works to put the serial port back to non-mux.

// terminate frame from section 6 of
// https://www.kernel.org/doc/Documentation/serial/n_gsm.txt
static const uint8_t gsm0710_terminate[] = {
0xf9, /* open flag /
0x03, / channel 0 /
0xef, / UIH frame /
0x05, / 2 data bytes /
0xc3, / terminate 1 /
0x01, / terminate 2 /
0xf2, / crc /
0xf9, / close flag */
};

int fd=0;

void signal_handler(int signum) {
int write_count;

/* terminate gsm 0710 multiplexing on the modem side */
write_count = write(fd, gsm0710_terminate, sizeof(gsm0710_terminate));
if (write_count != sizeof(gsm0710_terminate))
    fprintf(stderr, "Failed to terminate gsm multiplexing");

printf("cmux daemon exit!\n");
close(fd);
exit(0);

}