Re: [PATCH] Replace NULL thread handler with a dummy function.

Jonathan Cameron
2026-02-28T11:21:08Z

On Sat, 28 Feb 2026 12:15:51 +0200
Andy Shevchenko <andriy.shevchenko@intel.com> wrote:

> On Sat, Feb 28, 2026 at 10:36:46AM +0800, junan wrote:
> > Hi,
> >
Hi.

One general comment is to follow the formating of patch titles used in the
particular subsystem you are sending a patch to. So something like:

iio: hid-als: Provide a dummy thread handler to avoid warning.

> > This is a similar problem as [1]:
>
> > [1] https://lore.kernel.org/linux-iio/20260227071409.aEG-iBFD@linutronix.de/T/#m15ab81856b42f72169fe51bd87fa399b5147441f
> >
>
https://lore.kernel.org/all/20260220224514.471348-1-srinivas.pandruvada@linux.intel.com/

Is perhaps more relevant here and the preferred approach. These sensors should
in theory have never provided a trigger in the first place but we can't fix
that now because of ABI issues. The approach used in Srinivas' set gets us
to the position where the ABI remains the same but the underlying structure
correctly doesn't use a trigger.

I haven't checked how Srinivas' approach would apply here though so
I may well be missing something!
+CC Srinivas.

> Make it a Link tag.
>
> > without a threaded handler"), the IRQ core checks IRQF_ONESHOT flag
> > in IRQ request and gives a warning if there is no threaded handler.
> >
> > There are two iio devices on my machine:
>
> IIO
>
> > ```
> > junan@fedora:~$ ls /sys/bus/iio/devices/
> > iio:device0 trigger0
> > junan@fedora:~$ cat /sys/bus/iio/devices/*/name
> > als
> > als-dev0
> > ```
> >
> > The function calling chain is as following:
> >
> > hid_als_probe(hid-sensor-als.c)
> > => hid_sensor_setup_trigger(hid-sensor-trigger.c)
> > => iio_triggered_buffer_setup_ext(industrialio-triggered-buffer.c)
> >
> > `iio_triggered_buffer_setup_ext` is called with a NULL thread handler, and the flag is set to `IRQF_ONESHOT` inside it.

It's not as though the top half is valid here either! This is a completely
fake registration of an interrupt handler that never gets called.

>
> > I am not sure which flag to change, so I replace the NULL pointer with a
> > dummy function or can we just change the flag?
>
> Besides you used way too long lines, the last sentence (question) has to be
> located in the comment block...
>
> > Signed-off-by: junan <junan76@163.com>
> > ---
>
> ...somewhere here.
>
> And answering to it I think it's band-aid and wrong approach.
We need a bit of a band aid to avoid an ABI break, but the approach in Srinivas' patch
for the main hid sensors support is cleaner than the one here.

Jonathan

>