media: lirc: implement reading scancode

This implements LIRC_MODE_SCANCODE reading from the lirc device. The
scancode can be read from the input device too, but with this interface
you get the rc protocol, keycode, toggle and repeat status in addition
to just the scancode.

int main()
{
	int fd, mode, rc;
	fd = open("/dev/lirc0", O_RDWR);

	mode = LIRC_MODE_SCANCODE;
	if (ioctl(fd, LIRC_SET_REC_MODE, &mode)) {
		// kernel too old or lirc does not support transmit
	}
	struct lirc_scancode scancode;
	while (read(fd, &scancode, sizeof(scancode)) == sizeof(scancode)) {
		printf("protocol:%d scancode:0x%x toggle:%d repeat:%d\n",
			scancode.rc_proto, scancode.scancode,
			!!(scancode.flags & LIRC_SCANCODE_FLAG_TOGGLE),
			!!(scancode.flags & LIRC_SCANCODE_FLAG_REPEAT));
	}
	close(fd);
}

Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>