Re: A IIO trigger problem/bug.
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On 5/31/2012 4:56 PM, Ge Gao wrote:
It's been a while since I looked at this corner, but IIRC the basic principal is to prevent the driver read out code from being reentrant. Thus if your trigger is occuring faster than the driver isI met a strange problem concerning IIO driver. I wrote a driver that has trigger, ring buffer,just the standard way of doing things. It sometimes runs OK. However, I found sometimes, the trigger is NOT triggered at all. I am using a hardware interrupt to trigger a threaded ISR and post-ISR. I can see the interrupt coming correctly. By using "cat /proc/interrupts", I can see that the number of triggers stays the same while the number of interrupt increases steadily.
capable of reading from the device then triggers will be dropped.It's possible that we have a bug in there that means it is not succesfully recovering from the trigger being dropped.
One thought would be that you weren't clearing the interrupt unless a read occurs, but that doesn't seem to be the case here given you are seeing /proc/interrupts continue to increase...
The driver controls masking (typically through IRQF_ONESHOT) of an interrupt that is in turn fed by a second interrupt handler - the one in your driver handling the actual hardware interrupt.
I can't immediately spot why trig->usecount would be wrong. Just as a test could you drop the test for it entirely and see if that makes things work as expected? That will break having multiple users of the trigger, but might give us some clues as to what is happening. Otherwise, please add some printk's to the relevant places and lets see what is happening. With your usecase trig->use_count should only ever be 0 or 1 and if it is still 1 in iio_trigger_poll, we'll have some clue what is happening...
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