I have an embedded system (by NCR) which has 6 serial port (COM Port).
I was compile kernel (2.6.11.12) and activate the Extended 8250/16559
serial driver options, Support more than 4 legacy serial ports, sharing serial interupts and autodetect IRQ on standard ports. But still only
two serial ports is available (ttyS0 and ttyS1).

is there any solution ? i use Linux From Scratch distro.

If you do "ls /dev/ttyS*" are only the two serial ports shown?
If so you will need to create other ports with mkdev.

there is lot of ttySxx (created by udev), but only the first two is available
when i cat /dev/ttyS2 (and higher) it says "cat: /dev/ttyS2: Input/output error"

Post "ls -la /dev/ttyS*"

sh-3.00$ ls -la /dev/ttyS*
crw-rw---- 1 root dialout 4, 64 2006-08-09 12:05 /dev/ttyS0
crw-rw---- 1 root dialout 4, 65 2006-08-09 12:05 /dev/ttyS1
crw-rw---- 1 root dialout 4, 66 2006-08-09 12:05 /dev/ttyS2
crw-rw---- 1 root dialout 4, 67 2006-08-09 12:05 /dev/ttyS3
crw-rw---- 1 root dialout 4, 68 2006-08-09 12:05 /dev/ttyS4
crw-rw---- 1 root dialout 4, 69 2006-08-09 12:05 /dev/ttyS5
crw-rw---- 1 root dialout 4, 70 2006-08-09 12:05 /dev/ttyS6
crw-rw---- 1 root dialout 4, 71 2006-08-09 12:05 /dev/ttyS7

is there something wrong ?

The devices seem correct to me, same permissions, correct major and minor numbers.
You mention "an embedded system (by NCR) which has 6 serial port (COM Port)" and "i use Linux From Scratch distro". What is your actual hardware setup?
My serial port experience is working with multiport cards and text terminals.

nah ... that is the problem

i don't know the actual hardware specification, so i use all serial driver available
on the kernel 2.6.11.12.

the box is sealed and warranty void if opened, and no manual books ... think someone hide
it. in the rear of the box says:

---------------
NCR Corporation
Model: MV-0951A
---------------

..... mommy! (

There is nothing wrong from 'ls -l /dev/ttyS*'. It seems it gathered two extra ports. These ports might be on-board while the other six is from an expansion board. Write or use a program to test each port.

i tried using serial cable connected to another PC, then communicate it using minicom, and ... still ... only the first two port is usable, the another four is just stay like stupid.

when i activate the plug n play support in the kernel, in the message says (dmesg | grep tty)

ttyS0 at I/O 0x3f8 ( irq 4 ) is a 16550A
ttyS1 at I/O 0x2f8 ( irq 3 ) is a 16550A
ttyS0 at I/O 0x3f8 ( irq 4 ) is a 16550A
ttyS1 at I/O 0x2f8 ( irq 3 ) is a 16550A
ttyS14 at I/O 0x320 ( irq 5 ) is a 16550A
ttyS15 at I/O 0x328 ( irq 7 ) is a 16550A

and yes, only ttyS0 and ttyS1 is usable. Don't know why kernel detect ttyS14 not ttyS2.

BIOS setting for Serial Port:
com1 port 3f8 irq 4
com2 port 2f8 irq 3
com3 port 320 irq 5
com4 port 328 irq 5
com5 port 330 irq 5
com6 port 338 irq 5

If I understand your posts, you are running Linux From Scratch on the small embedded device with 6 serial ports but attempting to configure the serial ports as though you are using a PC that has 2 serial ports on the mainboard and an added serial card. I wonder if this is the correct way to configure it.
Was the BIOS setting the default or did you modify it?
Are the ttyS14 & 15 ports useable? How about if you creat devices for them?
I wonder if there is more context from dmesg about those serial ports?
If those are all from the same section then all the serial ports are listed with 2 of them duplicated and 2 identified that do not exist.
Looks like a configuration issue unless the device itself is somehow non-standard in the way the serial ports work.

Yes i use Linux From Scracth on the small embedded device with 6 serial port. Because the speed is slow (300Mhz) I use PC with 2 serial port to compile kernel and applications, then transfer it into the embedded device.

I have tried to use the BIOS default factory setting and customized setting, both didn't give any solution.

The ttyS14 and ttyS15 is unuseable. OK, here is the full dmesg output

http://krybrig.narod.ru/files/dmesg_output.txt