[CentOS] How do I configure additional serial ports?

[James Olin Oden]

On 3/12/07, Alfred von Campe <alfred at 110.net> wrote:
> On Mar 9, 2007, at 15:53, Matt Hyclak wrote:
>
> > Have you looked at http://wiki.centos.org/HowTos/Custom_Kernel?
>
> OK, I've rebuilt the kernel according to the instructions on this
> page (I ran into some issues; see earlier post in another thread).  I
> only changed two settings in the config file:
>
>   CONFIG_SERIAL_8250_MANY_PORTS=y    [originally disabled]
>   CONFIG_SERIAL_8250_NR_UARTS=20     [originally 4]
>
As I understand it you can also set the kernel command line arg
8250.nr_uarts equal to some value like 8, 16, 32, etc, without having
to rebuild your kernel (i.e. go into grub.conf and add to your kernel
line " 8250.nr_uarts=32").

> The good news is that the system now sees all eight serial ports
> (nine counting the one on the MB itself).  But the naming convention
> for the serial ports leaves something to be desired:
>
>   # dmesg | fgrep tty
>   ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
>   ttyS14 at I/O 0x5020 (irq = 177) is a 16C950/954
>   ttyS15 at I/O 0x5028 (irq = 177) is a 16C950/954
>   ttyS44 at I/O 0x5030 (irq = 177) is a 16C950/954
>   ttyS45 at I/O 0x5038 (irq = 177) is a 16C950/954
>   ttyS46 at I/O 0x5060 (irq = 193) is a 16450
>   ttyS47 at I/O 0x5068 (irq = 193) is a 16450
>   ttyS48 at I/O 0x5070 (irq = 193) is a 16450
>   ttyS49 at I/O 0x5078 (irq = 193) is a 16450
>   ttyS50 at I/O 0x50a0 (irq = 217) is a 16C950/954
>   ttyS51 at I/O 0x50a8 (irq = 217) is a 16C950/954
>   ttyS52 at I/O 0x50b0 (irq = 217) is a 16C950/954
>   ttyS53 at I/O 0x50b8 (irq = 217) is a 16C950/954
>   ttyS54 at I/O 0x50e0 (irq = 225) is a 16450
>   ttyS55 at I/O 0x50e8 (irq = 225) is a 16450
>   ttyS56 at I/O 0x50f0 (irq = 225) is a 16450
>   ttyS57 at I/O 0x50f8 (irq = 225) is a 16450
>
IIRC, what you have to do is create a udev rule so that you can cause
your serial port naming to persist the way you want.  I've never
created one myself, but we have done that in my group where I work, so
the problem is familiar to me.

Cheers...james