Re: uart_port structure in serial8250_port[i] doesn't have the port_type values

["V. Ananda Krishnan" <mansarov@us.ibm.com>]

On Mon, 2005-08-15 at 15:52 +0100, Russell King wrote:
> On Mon, Aug 15, 2005 at 09:10:56AM -0500, V. Ananda Krishnan wrote:
> >   The problem described here is related to the 8250_pci driver in
> > 2.6.12.3/2.6.12.4 kernels. When 8250_pci device driver detects a serial
> > port pci device and sets up the default setup (8250_pci.c), it tries to
> > find a match or unused port (serial8250_find_match_or_unused proc in in
> > 8250.c).
> > 
> > This leads to the uart_match_port with one of the parameters as
> > serial8250_ports[i].port. During debugging, I noticed that the none of
> > elements of the serial8250_ports[i].port.type was having any port value.
> 
> Every variable has a value.  In this case, they start off as PORT_UNKNOWN
> as expected.
> 
> > So the serial8250_register_port fails and the device driver module fails
> > to load.
> 
> I don't follow you here - failure of this function is not dependent on
> port.type being PORT_UNKNOWN.

Sorry for not being clear.  When 8250_pci.c invokes the function
serial8250_register_port(&serial_port) at line 1736 (linux-2.6.12.4), I
am seeing the following values: number of ports in the pci device is 1,
and the port structure has io_type:2, iobase:0, membase:80005000 and
mapbase:d6000000. In turn, The serial8250_register_port procedure in
8250.c calls the serial8250_find_match_or_unused(port) routine (line
2439 in 8250.c of linux-2.6.12.4) which returns 0. Hence the
uart_add_one_port(&serial8250_reg, &uart->port) (line 2455 in 8250.c of
linux-2.6.12.4) codes are not touched and serial8250_register_port
returns -28 (-ENOSPC) to the register_port caller.

Please let me know, if this is data is not clear and thanks for your
immediate attention.


> 
> > In this scenario, the last resort to find any entry which
> > doesn't have a real port associated with it also fails, because of the
> > null value in the serial8250_ports[i].port.type.
> 
> Again I don't follow you here.
> 
> The only reason serial8250_find_match_or_unused() will return NULL is
> if all registered port entries correspond with real hardware ports.
> In that case, the solution is to increase the number of 8250 ports
> via the kernels configuration.
> 
> > I would like to know when the port.type values in uart_8250_port structure
> > (in serial8250_ports[i]) is populated? Is there anything missing in the
> > serial8250_find_match_or_unused codes?  Any help to degug this problem
> > is appreciated. Thanks.
> 
> They're set to something other than PORT_UNKNOWN when a port is
> discovered via serial8250_register_port() / uart_add_one_port().
>