Re: [Sheflug] SuSE and serial ports

["Chris J/#6" <nospam [at] nccnet.co.uk>]

> Hi all
> 
> I am having a problem with SuSE 6.3 and serial ports, using "cu -l ttyS1" I
> get the response "port in use"
> 
> trying this with ttyS0 I can talk to the modem.
> 
> The system did have a mouse on ttyS1, but I have taken this out, connected
> the modem, stopped gpm, removed the /dev/mouse link, but it still won't
> work.
> 
> I have also switched to single user mode and checked the init scripts to
> make sure nothing is using the port. This also dosn't work so I tried a full
> reboot to switch off anything using the port, still no luck.
> 
> Any ideas please
> 

Type:
	lsof /dev/ttyS1 
which gives an output like:
	[189%][infinitum][chris] >lsof /dev/ttyS1
	COMMAND    PID USER   FD   TYPE DEVICE SIZE   NODE NAME
	pppd.bin 32525 root    0u   CHR   4,65      274106 /dev/ttyS1
	[190%][infinitum][chris] >

which shows me pppd.bin has /dev/ttyS1. Does lsof report anything to be 
talking to it ? Failing that, doing and "strace" is always useful as a 
diagnostic if you like lots of verbosity. strace will trace the system calls, 
so what you'll see will be a dump of the program's operation. Doing an 
'strace cat /dev/modem' whilst online (so pppd has /dev/modem) gives me (this 
is the last few lines):

brk(0x804b000)                          = 0x804b000
fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 1), ...}) = 0
open("/dev/modem", O_RDONLY)            = -1 EBUSY (Device or resource busy)
write(2, "cat: ", 5cat: )                    = 5
write(2, "/dev/modem", 10/dev/modem)              = 10
write(2, ": Device or resource busy", 25: Device or resource busy) = 25
write(2, "\n", 1
)                       = 1
close(1)                                = 0
_exit(1)                                = ?

So look for the 'open' which in this case reported EBUSY - this way if a 
device hasn't got the modem, it could be a dot-lock file which if exists 
causes cu to abort. With 'strace cu -l ttyS1' you should be able to locate 
the dot-lock or the actually problem causing it to abort.

'lsof', 'fuser', and 'strace' are very useful debugging tools :) Lsof 
especially ... it's *VERY* flexible and reports nearly everything that a 
process has open (files, devices, unix domain sockets, network sockets...).

Chris...

-- 
Chris Johnson            \  "If not for me then, do it for yourself. If not
sixie@nccnet.co.uk        \  for then do it for the world." -- Stevie Nicks
www.nccnet.co.uk/~sixie/   ~---------------------------------------+
Redclaw chat - http://redclaw.org.uk - telnet redclaw.org.uk 2000   \______


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