# [Solved] /dev/ttyS0 missing in kernel 2.6.31.7

## jagdpanther

After upgrading from kernel 2.6.31.6 to 2.6.31.7  (I used make oldconfig, so the kernel config didn't change much & I am using the kernel from kernel.org not Gentoo's.)  /dev/ttyS0 no longer exists.  ttyS1-ttyS3 devices exist (although there are no hardware ports to associate with them.)

The following two lines did show up in messages:

1247 Dec 12 06:33:05 runner kernel: serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A

1248 Dec 12 06:33:05 runner kernel: 00:08: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A

So the kernel still sees the device but no ttyS0 entry in /dev/

Any ideas?

(If I revert to 2.6.31.6 /dev/ttyS0 returns.)Last edited by jagdpanther on Tue Dec 15, 2009 8:02 pm; edited 1 time in total

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## 01allein

Why to use www.kernel.org instaead of Gentoos?

That way you save from problems.

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## jagdpanther

 *Quote:*   

> Why to use www.kernel.org instaead of Gentoos? 

 

I guess this is a little off topic and I hope I do not ruffle any feathers with my last reason below but here are three reasons that I use http://www.kernel.org kernels instead of gentoo:

1.  Sometimes I need the latest kernel for a new piece of hardware I am trying.

2.  I like to run almost the latest kernel to see if there are kernel compatibility issues with certain pieces of software (Like VMware, VirtualBox, nmap etc.) that I support at work.

3.  Kernel security issues seem to be addressed a little faster by using the latest stable kernel.org kernel.  

Back to the topic ...  any guesses on the lack of /dev/ttyS0?

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## boerKrelis

 *jagdpanther wrote:*   

> Any ideas?

 

Well, here's a 

```
# zgrep -i serial /proc/config.gz 

# CONFIG_SERIAL_NONSTANDARD is not set

# Serial drivers

CONFIG_SERIAL_8250=y

CONFIG_SERIAL_8250_CONSOLE=y

CONFIG_SERIAL_8250_PCI=y

CONFIG_SERIAL_8250_PNP=y

CONFIG_SERIAL_8250_NR_UARTS=4

CONFIG_SERIAL_8250_RUNTIME_UARTS=4

# CONFIG_SERIAL_8250_EXTENDED is not set

# Non-8250 serial port support

CONFIG_SERIAL_CORE=y

CONFIG_SERIAL_CORE_CONSOLE=y

# CONFIG_SERIAL_JSM is not set

# CONFIG_USB_SERIAL is not set

```

from a vanilla 

```

# uname -a

Linux xxxxx 2.6.32 #1 Thu Dec 3 13:11:21 CET 2009 i586 Geode(TM) Integrated Processor by AMD PCS AuthenticAMD GNU/Linux

```

which you could compare to your kernel config, as this one has a ttyS0 which I'm very much using ;-)

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## Hu

Since the functional and non-functional kernels are from the same major release (2.6.31.x), it should be viable to compare their respective configurations with diff -u.

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## jagdpanther

Diffing the 2.6.31.6 vs 2.6.31.7 kernel configuration files was a good idea.  However the only difference was the comment with the date and comment with the kernel version.  (This makes sense because I configured 2.6.31.7 with "make oldconfig").

I solved the issue by upgrading to 2.6.31.8.  (Was there a bug in .7?)

Thanks for the replies.

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