linux-kernel - Re: [PATCH] iio: light: ltr390: Add runtime PM support

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Message-ID: <CAE3SzaR14zWWM_g-H4C76+6fBDotuAux7n2V1g94R2xLFQZOYQ@mail.gmail.com>
Date: Tue, 26 Aug 2025 02:29:12 +0530
From: Akshay Jindal <akshayaj.lkd@...il.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: anshulusr@...il.com, dlechner@...libre.com, nuno.sa@...log.com, 
	andy@...nel.org, shuah@...nel.org, linux-iio@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: light: ltr390: Add runtime PM support

Hi Jonathan,
Thanks for your review. Please see my followup inline.

On Mon, Aug 25, 2025 at 7:56 PM Jonathan Cameron <jic23@...nel.org> wrote:
>
> On Fri, 22 Aug 2025 23:33:26 +0530
> Akshay Jindal <akshayaj.lkd@...il.com> wrote:
> > +
> > +     if (!state) {
> > +             ret = regmap_clear_bits(data->regmap, LTR390_INT_CFG, LTR390_LS_INT_EN);
> > +             data->irq_enabled = false;
>
> Just take an extra reference to runtime pm on enable of event and put it disable.
> Then no need for special handling with a local flag etc.

Consider a scenario, where the user only disables the event instead of
enabling it,
(i.e. user wrote 0 on the sysfs attribute before it was 1). In this case,
If enable means inc ref count and disable means dec ref count, then
this would lead to refcount underflow and the suspend callback will
not be called.

To handle this case, we would need to check whether irq/event was
enabled or not.
For that either we can use the local flag as I did, or I would need to
do a read and test
for the interrupt bit being set. I feel using the local flag would be
cleaner and would
require less code.
If you are fine with local flag usage, then shall I not stick to only
local flag usage?

Thanks,
Akshay