User Space GPIO Interrupt programming - GSoC-2018

[Dr. Rolf Jansen]

> Am 26.11.2020 um 16:56 schrieb Ian Lepore <ian at freebsd.org>:
> 
> On Tue, 2020-11-24 at 17:14 -0300, Dr. Rolf Jansen wrote:
>> Hello
>> 
>> Has anything of the GSoC-2018 efforts made it into the current code
>> base?
>> 
>> 
> https://wiki.freebsd.org/SummerOfCode2018Projects/UserSpaceGPIOinterrupts
>> 
>> I installed the recent 13.0-CURRENT snapshot (2020-11-19) on a
>> BeagleBone Black which was one of the implementation targets of said
>> project, but when running the test tools, I either see cannot
>> read/kevent/poll/aio_read - Operation not supported by device or
>> Inappropriate ioctl for device.
>> 
>> Perhaps I need to pull the project´s changes into the kernel by
>> myself. However, before this I would like to ask whether it is worth
>> the effort.
>> 
>> Please, can anyone shed some light on this.
>> 
>> Best regards
>> 
>> Rolf
>> 
> 
> I made some time this morning to review the gsoc2018 code.  It turns
> out this code is very high quality, nearly ready to commit as-is.  The
> main thing it needs is some style cleanup in its comment blocks, and
> documentation.  I'd be inclined to commit the code first and write the
> documentation over the next little while and commit it separately.
> 
> If you'd like to give it a try, here's a diff that should apply and
> build cleanly on freebsd 12 or 13:
> 
> https://people.freebsd.org/~ian/gpio_gsoc2018.diff
> 
> While there isn't any documentation yet, there is a test program (I
> haven't run it yet) that demonstrates all the features:
> 
> https://github.com/ckraemer/gsoc2018-utils/blob/master/src/gpioc_intr_test.c
> 
> Right now the code will let you block waiting for a pin-change event
> using select(), poll() or kevents, or to be notified via SIGIO, but
> after being notified that something happened, you still have to call
> read() to see which pin changed.  I think if the pin changes state
> multiple times between calls to read(), you'll lose track of some
> changes (I'm not positive of that, I don't understand the kevent stuff
> well).
> 
> I'd like to add some features so that you can configure it to track pin
> changes in counting-mode and timestamping-mode.  In counting mode, when
> you do a read() you would get back a pair of values, the pin number and
> how many times its interrupt fired since the last read.  In
> timestamping mode, every read would return a pin number and an
> associated timespec giving the exact time the interrupt happened (there
> would need to be a way to configure how many events it could buffer,
> but I think even allowing a thousand buffered events would only use a
> few kbytes of memory).

I got it working as well, please see my other post from yesterday. I used gpioc_intr_test.c.

I see hundreds of warning messages when I press the test button a few times. May these warnings be safely ignored. The kernel module of Oskar Holmund works quite nice as well (for what I need), and with that one, I don’t see warnings.

The counting- and timestamping-mode for sure would be very useful. Perhaps by implementing this, there won’t be no unhandled interrupts anymore, and hence there won’t be any warnings either.

Best regards

Rolf