2009/7/14, Martyn Welch <martyn.welch@xxxxxxxxxxx>:
> vichy wrote:
>
> > 2009/7/14, Martyn Welch <martyn.welch@xxxxxxxxxxx>:
> >
> > > vichy wrote:
> > >
> > >
> > > > Dear all:
> > > > while tracing 8250.c, serial8250_init, I find all the ports are
> > > > assigned with the same uart_driver 8250 as below:
> > > > static struct uart_driver serial8250_reg = {
> > > > .owner = THIS_MODULE,
> > > > .driver_name = "serial",
> > > > .dev_name = "ttyS",
> > > > .major = TTY_MAJOR,
> > > > .minor = 64,
> > > > .nr = UART_NR,
> > > > .cons = SERIAL8250_CONSOLE,
> > > > };
> > > >
> > > > what make me curious is the minor# above is 64, but the minor number
> > > > of /dev/ttyS1 is 65.
> > > >
> > > >
> > > >
> > > Numbering starts at 0, the first serial port (/dev/ttyS0) is assigned
> minor
> > > 64.
> > >
> > hi:
> > Thanks for your reminding.
> > What makes me curious is how kernel connect /dev/ttyS1 with serial driver?
> > By port number or minor number?
> >
> > I can see the minor of /dev/ttyS0 is 64, and serial driver is also
> > register as minor 64.
> > But what about /dev/ttyS1?
> >
>
> Ah, I think I understand. The above structure is related to the 8250
> driver, which is shared by all of the serial ports conforming to the "8250
> type" of serial port.
>
> Looking at serial8250_register_port()
> (http://lxr.linux.no/linux+v2.6.30/drivers/serial/8250.c#L3075),
> which seems to be where individual ports are registered, there is an array
> of type "uart_8250_port"
> (http://lxr.linux.no/linux+v2.6.30/drivers/serial/8250.c#L2632)
> which holds data pertaining to a specific port, which is then registered
> with the serial core
> (http://lxr.linux.no/linux+v2.6.30/drivers/serial/8250.c#L3116).
Hi:
thanks for your help.
I have 2 8250 serial devices.
and I want /dev/S1 to use the second 8250 device.
Should I
1. registering 2 ports in kernel and kernel will connect it to
/dev/ttyS1 automatically.
2. Or call 8250_init twice with and register uart_driver with minor number = 65?
if 1 is correct, can I boldly say the minor number of tty driver is meaningless?
if 2 is correct, what is the correct dev node we should create in /dev
about port2?
appreciate your help,
vichy
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