Re: xcam/xscanimage hangs w/ SANE 0.57

David Mosberger-Tang (davidm@azstarnet.com)
Fri, 30 May 1997 08:00:46 -0700

Mark> Hm, the /tmp/LOCK files do seem to be sticking around a long
Mark> time.

That's is normal and the intended behavior. The qcam backend uses
POSIX-style locking, _not_ the old Unix-style locking where the
presence of the file indicates a busy lock. With POSIX locking, there
is no point in removing the file.

Mark> OK, here it is... I started xcam, clicked "play", got one
Mark> image and the hang, then interrupted it with ^C:

Hmmh, there are lots of these:

Mark> [qcam] qc_send: sent 0x1d, camera echoed 0x78

Which indicates that the backend has a hard time reading the command
echos from the camera. You might want to play with qcam.c:qc_wait() a
little and see whether increasing the delay will fix the problem.
E.g., you could try something like this and then play with the loop
bound:

void
qc_wait (QC_Device *q)
{
extern void dummy (void);
int i;

for (i = 0; i < 50000; ++i)
dummy(); /* so this doesn't get optimized away */
}

void
dummy (void)
{
}

--david

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