Re: [PATCH 2/2] HID: i2c-hid: support the regulator

From	Benjamin Tissoires <benjamin.tissoires@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 2/2] HID: i2c-hid: support the regulator
Date	2016-09-14 16:40 +0200
Message-ID	<shjvY-215-3@gated-at.bofh.it> (permalink)
References	<sdNVD-3nb-1@gated-at.bofh.it> <sdNVE-3nb-3@gated-at.bofh.it> <shcXw-6ki-33@gated-at.bofh.it> <shdgS-6sF-29@gated-at.bofh.it> <shdqx-6LD-3@gated-at.bofh.it>
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On Sep 14 2016 or thereabouts, Brian Norris wrote:
> On Wed, Sep 14, 2016 at 03:55:05PM +0800, Brian Norris wrote:
> > The default behavior of regulator_get() is to provide a dummy regulator
> > if none is found. So the pointer is never NULL, and it won't break
> > devices without a regulator. If you don't want a dummy regulator you
> > would use regulator_get_optional() instead, and you would then need to
> > handle ERR_PTR(-ENODEV) specifically.
> 
> One caveat to the never-NULL comment above that I just noticed:
> 
> If CONFIG_REGULATOR=n, then regulator_get() actually returns NULL (see
> include/linux/regulator/consumer.h), but it also specifically has a
> comment right next to that NULL return, saying:
> 
>         /* Nothing except the stubbed out regulator API should be
>          * looking at the value except to check if it is an error
>          * value. Drivers are free to handle NULL specifically by
>          * skipping all regulator API calls, but they don't have to.
>          * Drivers which don't, should make sure they properly handle
>          * corner cases of the API, such as regulator_get_voltage()
>          * returning 0.
>          */
> 
> So, we still don't need to handle the NULL case specially.

Well, all the other regulator calls are either regulator_enable() or
regulator_disable(), which in this case (CONFIG_REGULATOR=n) are
returning 0.

So I think the whole patch is safe in its current form. Thanks for the
explanations.

Acked-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

Cheers,
Benjamin

> 
> Brian

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Re: [PATCH 2/2] HID: i2c-hid: support the regulator Benjamin Tissoires <benjamin.tissoires@redhat.com> - 2016-09-14 09:40 +0200
  Re: [PATCH 2/2] HID: i2c-hid: support the regulator Brian Norris <briannorris@chromium.org> - 2016-09-14 10:00 +0200
    Re: [PATCH 2/2] HID: i2c-hid: support the regulator Brian Norris <briannorris@chromium.org> - 2016-09-14 10:10 +0200
      Re: [PATCH 2/2] HID: i2c-hid: support the regulator Benjamin Tissoires <benjamin.tissoires@redhat.com> - 2016-09-14 16:40 +0200

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