linux-kernel - Re: [PATCH v5 3/3] iio: chemical: bme680: add power management

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Message-ID: <Z1d-r5DE159oEAdZ@vamoirid-laptop>
Date: Tue, 10 Dec 2024 00:35:11 +0100
From: Vasileios Amoiridis <vassilisamir@...il.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, lars@...afoo.de,
	robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
	u.kleine-koenig@...gutronix.de, linux-iio@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 3/3] iio: chemical: bme680: add power management

On Sun, Dec 08, 2024 at 05:33:36PM +0000, Jonathan Cameron wrote:
> On Tue, 3 Dec 2024 14:42:36 +0200
> Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:
> 
> > On Mon, Dec 02, 2024 at 09:35:50PM +0100, Vasileios Amoiridis wrote:
> > > On Mon, Dec 02, 2024 at 09:43:36PM +0200, Andy Shevchenko wrote:  
> > > > On Mon, Dec 02, 2024 at 08:23:41PM +0100, Vasileios Amoiridis wrote:  
> > > > > Add runtime power management to the device.  
> > 
> > ...
> > 
> > > > > +	ret = pm_runtime_resume_and_get(dev);
> > > > > +	if (ret)
> > > > > +		return ret;
> > > > > +
> > > > > +	ret = __bme680_read_raw(indio_dev, chan, val, val2, mask);
> > > > > +	pm_runtime_mark_last_busy(dev);
> > > > > +	pm_runtime_put_autosuspend(dev);  
> > > > 
> > > > Side note: as long as idle method is not defined (NULL) the above dance is
> > > > already taken into account in the regular put.  
> > 
> > > Thanks again for the review! Indeed by looking at the code a bit, it
> > > looks like the suspend callback is being called if the idle one is not
> > > found. But I have seen this dance that you mention much more often in
> > > the IIO that's why I used it. We can see what Jonathan has to say as
> > > well, I think what you propose, simplifies things.  
> > 
> > Yeah, this is cargo cult by many people (including me :-) who missed that
> > detail. If any, this can be addressed in a different series.
> > 
> > ...
> > 
> > > > > +static int bme680_buffer_preenable(struct iio_dev *indio_dev)
> > > > > +{
> > > > > +	struct bme680_data *data = iio_priv(indio_dev);
> > > > > +	struct device *dev = regmap_get_device(data->regmap);
> > > > > +	int ret;  
> > > >   
> > > > > +	ret = pm_runtime_resume_and_get(dev);
> > > > > +	if (ret)
> > > > > +		return ret;
> > > > > +
> > > > > +	return 0;  
> > > > 
> > > > Either this is broken (if the above can return positive codes), or can be
> > > > replaced with direct return:
> > > > 
> > > > 	return pm_...
> > > > 
> > > > (but I believe it's the former and you wanted something like if (ret < 0)
> > > >  there).
> > > >   
> > > > > +}  
> > > 
> > > Well, pm_runtime_resume_and_get() looks like it returns 0 on success and
> > > negative value on error so I think the if (ret) is correct, no? But I
> > > agree with you that it can be simplified as you proposed.  
> > 
> > Please, go ahead with the simplification!
> > 
> I tweaked it and applied the series to the togreg branch of iio.git and
> pushed out as testing for all the normal reasons.
> 
> There was some mess because of the EXPORT_SYMBOL() macro changes this raced
> against.  Please sanity check I didn't mess it up.
> 
> Jonathan
> 
>

Hi Jonathan,

Thank you for this! It looks good in the tree. 

Cheers,
Vasilis