serial console registration bugfix (2.6)

uart_set_options() can dereference a null pointer. This happens if you specify a console that hasn't previously been setup by early_serial_setup().

For example, on ia64, the HCDP typically tells us about line 0, so we calls early_serial_setup() for it. If the user specifies "console=ttyS3", we machine-check when trying to follow the uninitialized port->ops pointer.

It's not entirely clear to me whether we should return 0 or -ENODEV or something. The advantage of returning zero is that if the user specifies "console=ttyS0" and we just lack the HCDP, the console doesn't work as early as usual, but it does start working after the serial driver detects the port (though the baud/parity/etc from the command line are lost). Returning -ENODEV seems to prevent it from ever working.

Bjorn

=== drivers/serial/serial_core.c 1.72 vs edited ==--- 1.72/drivers/serial/serial_core.c Mon Sep 29 18:35:33 2003
+++ edited/drivers/serial/serial_core.c Thu Oct 16 09:56:55 2003
@@ -1859,6 +1859,9 @@
if (flow = 'r')
termios.c_cflag |= CRTSCTS;

+ if (!port->ops)
+ return 0;
+
port->ops->set_termios(port, &termios, NULL); co->cflag = termios.c_cflag;