On 04/09/2014 12:41 PM, Geert Uytterhoeven wrote:
> Dave: If I understand it correctly, you use console=ttyS2, while the kernel
> suddenly changed the order of the serial devices, so your port is no
> longer ttyS2, but ttyS4. Hence the serial port is not found, and
> uart_remove_one_port() is called on it, taking away your /dev/console for
> userspace?
Right.
> Why does the serial port driver call uart_add_one_port() for ports that
> don't exist?
> Or if it does exist ("inaccessible and buried inside the system somewhere"),
> how is it removed again?
The ones buried inside the system are immaterial here. I just wanted to
explain why I was using a separate PCI card instead of the other serial
ports.
>>From the backtrace, it's the call below to uart_remove_one_port()
> that removes the port?
>
> /**
> * serial8250_register_8250_port - register a serial port
> * @up: serial port template
> *
> * Configure the serial port specified by the request. If the
> * port exists and is in use, it is hung up and unregistered
> * first.
> *
> * The port is then probed and if necessary the IRQ is autodetected
> * If this fails an error is returned.
> *
> * On success the port is ready to use and the line number is returned.
> */
> int serial8250_register_8250_port(struct uart_8250_port *up)
> {
> ...
>
> if (uart && uart->port.type != PORT_8250_CIR) {
> if (uart->port.dev)
> uart_remove_one_port(&serial8250_reg, &uart->port);
>
> where was it added before?
Remember, serial8250_find_match_or_unused() will also reuse *EXISTING*
uart_ports if the port is of 'unknown' type.
I believe that port got added during the addition of the
serial8250_isa_devs, and now we're trying to reuse it since it is an
unknown port type.
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