Messages in this thread | | | Date | Wed, 09 Apr 2014 13:04:03 -0700 | From | Dave Hansen <> | Subject | Re: post 3.14 serial regression |
| |
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.
| |