Hi Dave,
On Wed, Apr 9, 2014 at 10:04 PM, Dave Hansen <dave@xxxxxxxx> wrote:
> 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.
Does it work with console=ttyS4?
>>>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.
So it gets added, removed, and added again.
I also noticed that unbinding and rebinding the driver doesn't re-attach it
as a serial console.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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