Re: [PATCH] hwmon: (corsair-psu) Fix failure to load when built-in to kernel

[Guenter Roeck]

On 12/8/23 05:57, Wilken Gottwalt wrote:
> On Fri, 8 Dec 2023 14:11:44 +0100
> Aleksa Savic <savicaleksa83@xxxxxxxxx> wrote:
>
> > On 2023-12-08 14:07:10 GMT+01:00, Aleksa Savic wrote:
> > > When built-in to the kernel, the corsair-psu driver fails to register with
> > > the following message:
> > >
> > > "Driver 'corsair-psu' was unable to register with bus_type 'hid'
> > > because the bus was not initialized."
> > >
> > > Fix this by initializing the driver after the HID bus using
> > > late_initcall(), as hwmon is built before HID.
> > >
> > > Fixes: d115b51e0e56 ("hwmon: add Corsair PSU HID controller driver")
> > > Signed-off-by: Aleksa Savic <savicaleksa83@xxxxxxxxx>
> > > ---
> > >   drivers/hwmon/corsair-psu.c | 15 ++++++++++++++-
> > >   1 file changed, 14 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/hwmon/corsair-psu.c b/drivers/hwmon/corsair-psu.c
> > > index 904890598c11..48831a528965 100644
> > > --- a/drivers/hwmon/corsair-psu.c
> > > +++ b/drivers/hwmon/corsair-psu.c
> > > @@ -899,7 +899,20 @@ static struct hid_driver corsairpsu_driver = {
> > >   	.reset_resume	= corsairpsu_resume,
> > >   #endif
> > >   };
> > > -module_hid_driver(corsairpsu_driver);
> > > +
> > > +static int __init corsairpsu_hid_init(void)
> > > +{
> > > +	return hid_register_driver(&corsairpsu_driver);
> > > +}
> > > +
> > > +static void __exit corsairpsu_hid_exit(void)
> > > +{
> > > +	hid_unregister_driver(&corsairpsu_driver);
> > > +}
> > > +
> > > +/* When compiled into the kernel, initialize after the hid bus */
> > > +late_initcall(corsairpsu_hid_init);
> > > +module_exit(corsairpsu_hid_exit);
> > >   
> > >   MODULE_LICENSE("GPL");
> > >   MODULE_AUTHOR("Wilken Gottwalt <wilken.gottwalt@xxxxxxxxxx>");
> >
> >
> > Woops! Just saw that the same fix was sent yesterday. Please disregard, sorry!
> >
> > Aleksa
>
> It is fine. I just start to wonder if there was a change in the subsystem. I
> used the driver as built-in in the past for several months and never had that
> issue. And now it is a real flood of reports.

Maybe there was a change in the build order, or some subtle change
in driver registration code. Question though is _when_ this changed.
It would be great if someone could bisect it. For example, bus registration
code has been changed significantly in v6.3. I am copying linux-input
and the hid maintainers for feedback.

Either case, I now have two patches and at least the first one was actually
tested, but no Reviewed-by: or Tested-by: for either of them. While that is
of course a formality, it would still be useful to show that it is not just
a random change.

Thanks,
Guenter