jarjar/libnfc
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

buses/uart: Use 'lockf()' for serial locking

Browse Source 
Using this standard Linux mechanism to lock serial ports has the advantage that if the process is killed the lock is automatically released.

Before a lock was simulated using the custom termios 'c_iflag' value 0x80000000, which has the disadvantage, other than being non-standard, that if the process is killed before closing the serial port, it would appear as locked and require manual cleanup of the flag.

Signed-off-by: Giovanni Giacobbi <giovanni@giacobbi.net>
This commit is contained in:
Giovanni Giacobbi 2021-04-13 12:13:20 +00:00
parent 2b5ad9ce0b
commit 7ff5d11127
No known key found for this signature in database
GPG Key ID: 63A98B68F17EE59B
1 changed files with 3 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
libnfc/buses/uart.c
View File

@ -92,9 +92,6 @@ const char *serial_ports_device_radix[] = { "ttyUSB", "ttyS", "ttyACM", "ttyAMA"
# define FIONREAD TIOCINQ # define FIONREAD TIOCINQ
#endif #endif
// Work-around to claim uart interface using the c_iflag (software input processing) from the termios struct
# define CCLAIMED 0x80000000
struct serial_port_unix { struct serial_port_unix {
int fd; // Serial port file descriptor int fd; // Serial port file descriptor
struct termios termios_backup; // Terminal info before using the port struct termios termios_backup; // Terminal info before using the port
@ -124,7 +121,7 @@ uart_open(const char *pcPortName)
return INVALID_SERIAL_PORT; return INVALID_SERIAL_PORT;
} }
// Make sure the port is not claimed already // Make sure the port is not claimed already
if (sp->termios_backup.c_iflag & CCLAIMED) { if (lockf(sp->fd, F_TLOCK, 0)) {
uart_close_ext(sp, false); uart_close_ext(sp, false);
return CLAIMED_SERIAL_PORT; return CLAIMED_SERIAL_PORT;
} }
@ -132,7 +129,7 @@ uart_open(const char *pcPortName)
sp->termios_new = sp->termios_backup; sp->termios_new = sp->termios_backup;
sp->termios_new.c_cflag = CS8 | CLOCAL | CREAD; sp->termios_new.c_cflag = CS8 | CLOCAL | CREAD;
sp->termios_new.c_iflag = CCLAIMED | IGNPAR; sp->termios_new.c_iflag = IGNPAR;
sp->termios_new.c_oflag = 0; sp->termios_new.c_oflag = 0;
sp->termios_new.c_lflag = 0; sp->termios_new.c_lflag = 0;
@ -282,6 +279,7 @@ uart_close_ext(const serial_port sp, const bool restore_termios)
if (UART_DATA(sp)->fd >= 0) { if (UART_DATA(sp)->fd >= 0) {
if (restore_termios) if (restore_termios)
tcsetattr(UART_DATA(sp)->fd, TCSANOW, &UART_DATA(sp)->termios_backup); tcsetattr(UART_DATA(sp)->fd, TCSANOW, &UART_DATA(sp)->termios_backup);
lockf(UART_DATA(sp)->fd, F_ULOCK, 0);
close(UART_DATA(sp)->fd); close(UART_DATA(sp)->fd);
} }
free(sp); free(sp);