We are running kernel 2.4.8 on the sh4 platform.
We are encoutering a problem with the cs4281
driver as described in the following:
The device file is opened normally. Everything
is working fine. Then, when it is closed, the
application hangs. A ctrl-C is required to get
out of it. Upon further examining, we find that
the close() call is not returning. It is stuck
at the drain_adc().
In the cs4281_release(),
...
if (file->f_mode & FMODE_READ) {
------> drain_adc(s, file->f_flags & O_NONBLOCK);
down(&s->open_sem_adc);
stop_adc(s);
...
And in the drain_adc(),
...
for (;;) {
set_current_state(TASK_INTERRUPTIBLE);
spin_lock_irqsave(&s->lock, flags);
-----> count = s->dma_adc.count;
CS_DBGOUT(CS_FUNCTION, 2,
printk(KERN_INFO "cs4281: drain_adc() %d\n",
count));
spin_unlock_irqrestore(&s->lock, flags);
...
It seems that since s->dma_adc.count=8192, we
are going into an infinite loop there, in
drain_adc(),
The work-around that we are currently looking
at is setting the flag to O_NONBLOCKING just
prior to closing the device to take advantages
of this.
...
if (nonblock) {
remove_wait_queue(&s->dma_adc.wait, &wait);
current->state = TASK_RUNNING;
return -EBUSY;
}
...
Unfortunately, it causes problems later
since it is in non-blocking mode. Do a
fcntl(fd, F_SETFL, 0);
did not reset to the normal/blocking mode.
What would be the proper way to handle this
situation? Since I am not familiar with the
driver, I don't know if removing the
drain_adc() from cs4281_release() would cause
problems later or not. I am also not sure
this behavior is specific to the sh4-linux
port or not.
Appreciate any suggestions/comments.
Regards.
Bao
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This archive was generated by hypermail 2b29 : Sat Sep 15 2001 - 21:00:42 EST