serial over /dev/ttyu0 does not work.

[Marcel Moolenaar]

On May 19, 2007, at 8:26 AM, Stefan Lambrev wrote:

> I have disabled device sio in kernel and replaced it with device uart.
>
> And so dmesg |grep uart is :
>
> uart0: <16550 or compatible> port 0x3f8-0x3ff irq 4 on acpi0
>
> I was expecting to see uart1 too .. but it is not here.

It's likely that the port doesn't exist or you disabled it
in the BIOS. With ACPI you can be sure we won't try to
create a device for hardware that isn't described by ACPI.

> I have: /dev/ttyu0 & /dev/cuau0, also in /etc/ttys I have the  
> following line:
> ttyu0   "/usr/libexec/getty std.9600"   vt100   on  secure

> I have this configuration on other servers too and it works without  
> problems,
> but the main difference that I found is when I use minicom.

> I think if I try to open /dev/cuau0 I should see "Device busy" -  
> and on all other servers where I checked
> it does respond with "Device busy" as it is already used, but on  
> this server I do not!

Are you sure your minicom configuration is correct? Could it
be that it still tries to open ttyd0?

> Also I notice that where the serial is NOT working I have this line  
> in ps xa:
> 1653  ??  I      0:00.00 /usr/libexec/getty std.9600 ttyu0
> In first moment I thought it is OK to have getty on ttyu0, but what  
> is this "??" :)

It means that there's no terminal associated with the getty process.
It's perfectly normal.

> so I checked on the other server and I saw that there is NO getty  
> on ttyu0 running at all (it is started
> when I start minicom from the other side of the serial but then it  
> shows:
> 99615  u0  Ss+    0:00.00 /usr/libexec/getty std.9600 ttyu0
> and it is stopped when I stop minicom)

Interesting. How is getty started exactly?
BTW: In this case getty is associated with ttyu0 itself. That's not
uncommon and happens when you manually start and/or stop getty.

> Any useful ideas where to look for ? Also switching back from uart  
> to sio may sound OK, but it needs another restart :(

The problem doesn't seem to be with uart(4). I see getty(8) and
minicom(1) behaviour that's different on this box from other
boxes (as per your description). It looks to me to be a config
problem.

-- 
Marcel Moolenaar
xcllnt at mac.com