Re: [PATCH 00/10] platform/x86: toshiba_acpi: move acpi add/remove to device-managed routines

[Alexandru Ardelean <ardeleanalex@gmail.com>]

On Tue, Mar 30, 2021 at 11:21 AM Hans de Goede <hdegoede@redhat.com> wrote:
>
> Hi Alexadru, Jonathan,
>
> On 3/24/21 1:55 PM, Alexandru Ardelean wrote:
> > This changeset tries to do a conversion of the toshiba_acpi driver to use
> > only device-managed routines. The driver registers as a singleton, so no
> > more than one device can be registered at a time.
> >
> > My main intent here is to try to convert the iio_device_alloc() and
> > iio_device_register() to their devm_ variants.
> >
> > Usually, when converting a registration call to device-managed variant, the
> > init order must be preserved. And the deregistration order must be a mirror
> > of the registration (in reverse order).
> >
> > This change tries to do that, by using devm_ variants where available and
> > devm_add_action_or_reset() where this isn't possible.
> > Some deregistration ordering is changed, because it wasn't exactly
> > mirroring (in reverse) the init order.
> >
> > For the IIO subsystem, the toshiba_acpi driver is the only user of
> > iio_device_alloc(). If this changeset is accepted (after discussion), I
> > will propose to remove the iio_device_alloc() function.
> >
> > While I admit this may look like an overzealous effort to use devm_
> > everywhere (in IIO at least), for me it's a fun/interesting excercise.
>
> Alexadru, thank you for the patches.
>
> Jonathan, thank you for the reviews.
>
> To be honest I'm currently inclined to not accept / merge these patches,
> this is based on 2 assumptions from me, which might be wrong. let me explain.
>
> If I understand things correctly, the main reason for this rework of
> the toshiba_acpi code is to move iio_device_alloc() and iio_device_register()
> to their devm_ variants, converting the last users in the tree ?

yes
well, we still have plenty of users iio_device_alloc() /
iio_device_register() inside drivers/iio

but the toshipa_acpi driver is the more quirky user of these functions
[treewide]

i wanted to jump on those simpler IIO cases, but i thought i would
leave those to new contributors [for a while];
the complexity of those conversions is good enough to get some people
started to contribute changes that are a bit more useful than
checkpatch fixes, comment fixes [etc];

[personally] i feel that these devm_ conversions are complex enough to
maybe get people wanting to dig more into some kernel design stuff

>
> This would allow these 2 iio functions to then be e.g. marked as static /
> private helpers inside the iio core, so that all new users can only use
> the devm_ versions. But if I'm reading Jonathan's reaction correctly then
> Jonathan is not planning to do that because they might still be useful
> in some cases.
>
> Jonathan have I correctly understood that you don't plan to make any
> changes to the iio_device_alloc() and iio_device_register() functions
> even if this gets merged ?
>
> Which brings me to my next assumption, Alexandru, I don't read anything
> about testing anywhere. So I'm currently under the assumption that
> you don't have any hardware using the toshiba_acpi driver and that this
> is thus untested ?

yes, i don't have any hw to test this

>
> The not being tested state is my main reason for not wanting to merge
> this. The toshiba_acpi driver likely does not have a whole lot of users,
> so the chances of someone running release candidates or even just the
> latest kernels on hardware which uses it are small.  This means that if
> we accidentally introduce a bug with this series it might not get caught
> until say lots of people start upgrading to Ubuntu 22.04 which is
> the first Ubuntu kernel with your changes; and then at least one of the
> hit users needs to have the skills to find us and get in contact about that.
>
> TL;DR: we might break stuff and if we do it might be a long time until we
> find out we did and then we have been shipping broken code for ages...

ack
well, i don't insist in pushing this series;

another thought was to just send bits of this set, which are simple
enough to consider even on their own;

maybe i'll look for a toshiba laptop with support for this stuff;
i'll see

thanks :)
Alex

>
> Regards,
>
> Hans
>
>
>
>
>
> >
> > Alexandru Ardelean (10):
> >   platform/x86: toshiba_acpi: bind life-time of toshiba_acpi_dev to
> >     parent
> >   platform/x86: toshiba_acpi: use devm_add_action_or_reset() for
> >     singleton clear
> >   platform/x86: toshiba_acpi: bind registration of miscdev object to
> >     parent
> >   platform/x86: toshiba_acpi: use device-managed functions for input
> >     device
> >   platform/x86: toshiba_acpi: register backlight with device-managed
> >     variant
> >   platform/x86: toshiba_acpi: use devm_led_classdev_register() for LEDs
> >   platform/x86: toshiba_acpi: use device-managed functions for
> >     accelerometer
> >   platform/x86: toshiba_acpi: use device-managed for wwan_rfkill
> >     management
> >   platform/x86: toshiba_acpi: use device-managed for sysfs removal
> >   platform/x86: toshiba_acpi: bind proc entries creation to parent
> >
> >  drivers/platform/x86/toshiba_acpi.c | 249 +++++++++++++++++-----------
> >  1 file changed, 150 insertions(+), 99 deletions(-)
> >
>