Re: [libgpiod] - fast writing while waiting for edge events

[Mathias Dobler <mathias.dob@xxxxxxxxx>]

> Firstly note that you cannot lose edge events. They are queued in the
> kernel in case userspace is a bit busy.  It is still possible to overflow
> the queue, but it takes serious effort.  You can check the seqnos in the
> events to detect an overflow.

I think the only thing that is lost is my memory sometimes.

> It is also a bit odd to be monitoring a line for edges AND polling it
> at the same time.  You get edge events when it changes value, so polling
> between edges is redundant.

Yeah, I might have to rethink my usage there...

> Though if you are using a libgpiod function to perform the wait you are
> still stuck, as going by the documentation you have to prevent other
> access while you are waiting....

> So you have to not use a libgpiod function and wait by poll()ing the
> request fd.
> At that point you may as well wait on both requests in the one thread.
> And then you don't need the mutex as you only have one thread accessing the
> requests.

I see. So that means waiting on the request fd is not affected by the
threading contract?
Thanks for your help.

Mathias