On Sat, Apr 20, 2024 at 10:38:24PM +0200, Aleksander Mazur wrote:
> Dnia 2024-04-20, o godz. 11:14:06
> Guenter Roeck <linux@xxxxxxxxxxxx> napisał(a):
>
> > On Sat, Apr 20, 2024 at 06:34:27PM +0200, Aleksander Mazur wrote:
> > > Hello,
> > >
> > > I have a Wyse C00X thin client which is apparently equipped with GMT g781.
> > > It is (or used to be) supported by lm90 driver. (I have a log from 2020
> > > where it was simply working fine; it was kernel version 5.6.0 then.)
> > > Now, with 6.8.7, I get following error:
> > >
> > > > lm90 0-004c: Failed to enable regulator: -ENODEV
> > >
> > > However, when I just turned this message into a warning and let the driver
> > > continue, it seems to work fine, providing temp1 and temp2 as previously.
> > >
> > > Do you have an idea what could cause such a regression, and if this change
> > > (I mean: simply not returning error from devm_regulator_get_enable) is safe?
> > >
> >
> > Do you have CONFIG_REGULATOR enabled in your system ?
> >
> > Guenter
>
> No, it's disabled (and it was disabled in 5.6.0 as well).
>
I thought so. It works in v6.1 and earlier kernels because
devm_regulator_get() returns NULL if CONFIG_REGULATOR=n.
The driver used that function prior to commit ad804a4d82fc
("hwmon: (lm90) simplify using devm_regulator_get_enable()").
> Shouldn't devm_regulator_get_enable*() stubs return success instead of -ENODEV?
>
One might think so, but apparently the author thought otherwise. It looks
like the function can not be used for drivers which have to work with
CONFIG_REGULATOR=n. The only option I can see is to revert commit
ad804a4d82fc because that commit doesn't just simplify the code but also
make regulator support mandatory. Matti, do you have a better idea ?
Other hwmon drivers are affected as well, so we'll need a common solution.
Aleksander, for your use case, you can just drop the offending code
until the fix (or revert) makes it upstream. Sorry for the trouble.
Thanks,
Guenter
