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

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Date:	Mon, 25 Mar 2013 14:26:06 +0800
From:	Zhang Rui <rui.zhang@...el.com>
To:	"R, Durgadoss" <durgadoss.r@...el.com>
Cc:	Eduardo Valentin <eduardo.valentin@...com>,
	"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

On Mon, 2013-03-25 at 00:20 -0600, R, Durgadoss wrote:
> > -----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 ?
> 

probably it is because one driver want to get the temperature of a
sensor registered by another driver.

thanks,
rui

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