Serial port problem

[Ian Leonard <ian@smallworld.cx>]

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.