linux-kernel - Re: [PATCH v7] iio: light: ltr390: Implement runtime PM support

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Message-ID: <20250910195232.173ff14f@jic23-huawei>
Date: Wed, 10 Sep 2025 19:52:32 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Akshay Jindal <akshayaj.lkd@...il.com>
Cc: Jonathan Cameron <jonathan.cameron@...wei.com>, Andy Shevchenko
 <andy.shevchenko@...il.com>, 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 v7] iio: light: ltr390: Implement runtime PM support

On Wed, 10 Sep 2025 23:30:36 +0530
Akshay Jindal <akshayaj.lkd@...il.com> wrote:

> Hi Jonathan,
> Seeking your approval. If there is a requirement for v8, I can send that too.

Wait a day or so just to see if Andy is fine with your reply to him.

Thanks,

Jonathan

> 
> Thanks,
> Akshay
> 
> On Wed, Sep 10, 2025 at 4:32 PM Jonathan Cameron
> <jonathan.cameron@...wei.com> wrote:
> >
> > On Wed, 10 Sep 2025 10:17:00 +0300
> > Andy Shevchenko <andy.shevchenko@...il.com> wrote:
> >  
> > > On Tue, Sep 9, 2025 at 10:47 PM Akshay Jindal <akshayaj.lkd@...il.com> wrote:  
> > > >
> > > > Implement runtime power management for the LTR390 sensor. The device
> > > > autosuspends after 1s of idle time, reducing current consumption from
> > > > 100 µA in active mode to 1 µA in standby mode as per the datasheet.
> > > >
> > > > Ensure that interrupts continue to be delivered with runtime PM.
> > > > Since the LTR390 cannot be used as a wakeup source during runtime
> > > > suspend, therefore increment the runtime PM refcount when enabling
> > > > events and decrement it when disabling events or powering down.
> > > > This prevents event loss while still allowing power savings when IRQs
> > > > are unused.  
> > >
> > > ...
> > >  
> > > > +static int ltr390_read_raw(struct iio_dev *iio_device,
> > > > +                          struct iio_chan_spec const *chan, int *val,
> > > > +                          int *val2, long mask)  
> > >
> > > Isn't the mask unsigned long? Jonathan, do we get this fixed already?  
> >
> > Whilst it could (and probably should) be unsigned, it's not actually a mask.
> > That naming is a historical mess up / evolution thing - long ago it was a bitmap.
> > It is now the index of a bit in the mask.  So this is unrelated(ish) to the
> > recent fixes around the actual bitmaps/bitmasks.
> >
> > Changing this one is a lot more painful than the recent fix to the infomask
> > as it means changing the signature in every driver.
> > I'm doubtful on whether this one is worth the churn.  
>