serial port problem

serial port problem

[Dmitry Melekhov]

Hello!

I have problems with connecting to any equipment since kernel 2.6.24
(Ubuntu 8.04)-
if I connect cisco switch or router I can't do anything with it, but
when I boot previos kernel (from Ubuntu 7.10 )
all is OK.
Today I did upgrade to Ubuntu 8.10 (kernel 2.6.27) and still have the
same problem.
So I downloaded and installed kernel 2.6.27.4 and still have the same
problem.
I connected zyxel modem to port and I see that it gets commsnds- it's
data lamp blinks, but I get nothing.
Situation is different on my colleague machine- since ubuntu 8.04 he can
see in minicom or gtkterm how  connected router boots,
but then he can't send someting over several port to router.
I created bug report in ubuntu's launchpad, but there is no solution.
As I now see this problem exists with kernel from kernel.org could you
tell me how can I find where problem is?

Thank you!

Re: serial port problem

[Adam Nielsen]

> I connected zyxel modem to port and I see that it gets commsnds- it's
> data lamp blinks, but I get nothing.
> Situation is different on my colleague machine- since ubuntu 8.04 he can
> see in minicom or gtkterm how  connected router boots,
> but then he can't send someting over several port to router.
> I created bug report in ubuntu's launchpad, but there is no solution.
> As I now see this problem exists with kernel from kernel.org could you
> tell me how can I find where problem is?

I had a similar problem trying to get a dial-up modem working a couple 
of months ago.  I could use minicom to connect to the modem and type AT 
commands and read the responses, but whenever I dialled up I would see 
"CONNECT 48000" and that would be it.  I couldn't send or receive data 
from the other end.  After about a minute the ISP I was calling would 
time out and disconnect me.

I have no idea what the problem was, I even went to the trouble of 
buying extra serial ports on a PCI card thinking the hardware was 
faulty, but nothing helped.  In the end I downgraded to 2.6.17.8 (as 
this version was running on another PC that worked fine with the modem) 
and suddenly the whole thing worked perfectly.

So it looks like some bug was introduced into the serial driver at some 
point, and if you're having problems it must still be in the current 
kernel version.  I would suggest trying 2.6.17.8 instead (as that worked 
for me), and if it works for you too you might want to try upgrading 
until you find which version stops working - then we will know when the 
problem was first introduced.

Cheers,
Adam.

Serial port problem

[Ian Leonard]

Hi,

The trouble started when I upgraded a machine from FC3 to FC4. It had a 
serial touchscreen. With FC4 it stopped working completely. I added 
debug to the X input driver and found read() permanently blocked despite 
the file having been opened with O_NDELAY.

I then tried a simple test with two machine connected with a serial 
cable and using minicom to send characters both ways. One was a laptop. 
If you typed from the failing machine to the laptop all was well. Typing 
the other way caused one character to be displayed and then it hung 
(although I could use 'cat >/dev/ttyS0' to send data just fine).

I then repeated the test using 4 different motherboards. 2 exhibited the 
problem 2 didn't. So to recap, sending data without changing the driver 
settings (stty) seems to work. Configuring the port seems to cause a 
problem on some motherboards. One of those is a VIA mini-itx. The other 
is more standard Gigabyte.

I have tried using the standard FC4 kernel and 2.6.15.6.

Not sure what to try next, so any pointer gratefully received.


-- 
Ian Leonard

Please ignore spelling and punctuation - I did.

Serial Port problem

[Vinayak P Risbud]

         Hi,

    How to change the serial port driver ?
    I mean,  I have written a dummy simple serial
    port driver.   I want,  my driver to respond
    for any activity on COM1 and COM2,  instead
    of standard serial driver,  that comes along with
    Linux kernel.

    How can I do this ?

        Thanks in advance
            Vinayak