linux-kernel - RE: [PATCH 1/2] thermal: introduce thermal_zone_lookup

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Date:	Mon, 25 Mar 2013 06:20:27 +0000
From:	"R, Durgadoss" <durgadoss.r@...el.com>
To:	"Zhang, Rui" <rui.zhang@...el.com>,
	Eduardo Valentin <eduardo.valentin@...com>
CC:	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/2] thermal: introduce thermal_zone_lookup_temperature
 helper function

> -----Original Message-----
> From: linux-pm-owner@...r.kernel.org [mailto:linux-pm-
> owner@...r.kernel.org] On Behalf Of Zhang Rui
> Sent: Monday, March 25, 2013 11:41 AM
> To: Eduardo Valentin
> Cc: linux-pm@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH 1/2] thermal: introduce
> thermal_zone_lookup_temperature helper function
> 
> On Fri, 2013-03-22 at 17:13 -0400, Eduardo Valentin wrote:
> > This patch adds a helper function to get temperature of
> > a thermal zone, based on the zone type name.
> >
> > It will perform a zone name lookup and return the last
> > sensor temperature reading. In case the zone is not found
> > or if the required parameters are invalid, it will return
> > the corresponding error code.
> >
> > Signed-off-by: Eduardo Valentin <eduardo.valentin@...com>
> > ---
> >  drivers/thermal/thermal_sys.c |   32
> ++++++++++++++++++++++++++++++++
> >  include/linux/thermal.h       |    1 +
> >  2 files changed, 33 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/thermal/thermal_sys.c b/drivers/thermal/thermal_sys.c
> > index 5bd95d4..f0caa13 100644
> > --- a/drivers/thermal/thermal_sys.c
> > +++ b/drivers/thermal/thermal_sys.c
> > @@ -1790,6 +1790,38 @@ void thermal_zone_device_unregister(struct
> thermal_zone_device *tz)
> >  }
> >  EXPORT_SYMBOL_GPL(thermal_zone_device_unregister);
> >
> > +/**
> > + * thermal_lookup_temperature - search for a zone and returns its
> temperature
> > + * @name: thermal zone name to fetch the temperature
> > + * @temperature: pointer to store the zone temperature, in case it is
> found
> > + *
> > + * When the zone is found, updates @temperature and returns 0.
> > + *
> > + * Return: -EINVAL in case of wrong parameters, -ENODEV in case the
> zone
> > + * is not found and 0 when it is successfully found.
> > + */
> > +int thermal_zone_lookup_temperature(const char *name, int
> *temperature)
> > +{
> > +	struct thermal_zone_device *pos = NULL;
> > +	bool found = false;
> > +
> > +	if (!name || !temperature)
> > +		return -EINVAL;
> > +
> > +	mutex_lock(&thermal_list_lock);
> > +	list_for_each_entry(pos, &thermal_tz_list, node)
> > +		if (!strcmp(pos->type, name)) {
> > +			found = true;
> > +			break;
> > +		}
> > +	if (found)
> > +		*temperature = pos->last_temperature;
> > +	mutex_unlock(&thermal_list_lock);
> > +
> > +	return found ? 0 : -ENODEV;
> > +}
> > +EXPORT_SYMBOL_GPL(thermal_zone_lookup_temperature);
> > +
> please do not use thermal zone type as the parameter because unique
> thermal zone type string is not a hard rule.

Okay, agree with this. This is what I am implementing in
my changes as well.

> If this is really needed, I'd prefer two APIs instead
> 1. struct thermal_zone_device * thermal_zone_get_zone_by_name(char
> *name);
> 2. int thermal_zone_get_temperature(struct thermal_zone_device *, int
> *temperature);

Why do we need this second API?
If the driver has a 'tz' pointer, it can use tz->ops->get_temp
to retrieve the temperature, right ?

Thanks,
Durga