Messages in this thread | | | Date | Wed, 21 Apr 2004 11:59:51 +0200 | From | Petr Slansky <> | Subject | PROBLEM: serial port loopback serious bug |
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Description:
I observe the bug in kernel 2.4.21 and 2.4.22, I guess it is general problem in 2.4.xx kernel. Command 'cat file >/dev/ttyS0' sends the first 4096 bytes again and again...
DETAILS:
I have generic serial port on i586 machine (PC). I created loopback cable (TX-RX and RTS-CTS pins connected) and conected the cable to serial port ttyS0. Simple serial port loopback.
Configuration: #stty 38400 raw clocal crtscts </dev/ttyS0
Command in console1 (capture ttyS0 to file): #cat /dev/ttyS0 > fileI.bin
Command in console2 (send a longer file to ttyS0): #cat fileO.bin >/dev/ttyS0
The file fileO.bin have to be at least 4096 bytes long.
I guess you know what is expected result but I bet you don't know real result under Linux. I will tell you. Only first 4096 bytes are sent to /dev/ttyS0. After that this sequence is read from /dev/ttyS0 again and again..., even when no data are send to /dev/ttyS0 anymore. I tested this sequence on FreeBSD 4.9 too and I had no problem with loopback like this there. Something is seriosly wrong in kernel 2.4.x What about 2.6.x??
With regards, Petr
--------------------------------- Petr Slansky, slansky@usa.net ---------------------------------
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