Re: [PATCHv2 1/3] thermal: introduce thermal_zone_get_zone_by_namehelper function

[Eduardo Valentin]

On 04-04-2013 13:12, R, Durgadoss wrote:
> > -----Original Message-----
> > From: Eduardo Valentin [mailto:eduardo.valentin@xxxxxx]
> > Sent: Thursday, April 04, 2013 3:43 AM
> > To: Zhang, Rui
> > Cc: linux-pm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; R, Durgadoss;
> > Eduardo Valentin
> > Subject: [PATCHv2 1/3] thermal: introduce
> > thermal_zone_get_zone_by_name helper function
> >
> > This patch adds a helper function to get a reference of
> > a thermal zone, based on the zone type name.
> >
> > It will perform a zone name lookup and return a reference
> > to a thermal zone device that matches the name requested.
> > In case the zone is not found or when several zones match
> > same name or if the required parameters are invalid, it will return
> > the corresponding error code (ERR_PTR).
> >
> > Signed-off-by: Eduardo Valentin <eduardo.valentin@xxxxxx>
> > ---
> >   drivers/thermal/thermal_sys.c |   34
> > ++++++++++++++++++++++++++++++++++
> >   include/linux/thermal.h       |    1 +
> >   2 files changed, 35 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/thermal/thermal_sys.c b/drivers/thermal/thermal_sys.c
> > index 5bd95d4..6e1da0a 100644
> > --- a/drivers/thermal/thermal_sys.c
> > +++ b/drivers/thermal/thermal_sys.c
> > @@ -1790,6 +1790,40 @@ void thermal_zone_device_unregister(struct
> > thermal_zone_device *tz)
> >   }
> >   EXPORT_SYMBOL_GPL(thermal_zone_device_unregister);
> >
> > +/**
> > + * thermal_zone_get_zone_by_name() - search for a zone and returns its
> > ref
> > + * @name: thermal zone name to fetch the temperature
> > + *
> > + * When only one zone is found with the passed name, returns a reference
> > to it.
> > + *
> > + * Return: On success returns a reference to an unique thermal zone with
> > + * matching name equals to @name, a ERR_PTR otherwise.
> > + */
> > +struct thermal_zone_device *thermal_zone_get_zone_by_name(const
> > char *name)
> > +{
> > +	struct thermal_zone_device *pos = NULL, *ref = ERR_PTR(-EINVAL);
> > +	int found = 0;
> > +
> > +	if (!name)
> > +		goto exit;
> > +
> > +	mutex_lock(&thermal_list_lock);
> > +	list_for_each_entry(pos, &thermal_tz_list, node)
> > +		if (!strnicmp(name, pos->type, THERMAL_NAME_LENGTH)) {
> > +			found++;
> > +			ref = pos;
> > +		}
> > +	mutex_unlock(&thermal_list_lock);
> > +
> > +	/* Success only when an unique zone is found */
> > +	if (found != 1)
> > +		ref = ERR_PTR(-ENODEV);
>
> I think we should differentiate between the two cases:
> 1. The zone does not exist at all
> 	return NULL in this case
> 2. There are multiple zones
> 	return ERR_PTR(-EEXIST) in this case
>
> This way the calling function can figure out the exact reason
> for failure.

I think the code documentation is already clear enough to say that this 
is for unique matches. But in case you want to differentiate these 
cases, I can resend it. Do you have a usage for this?

Besides, I would prefer to return ERR_PTR(-ENODEV) in the first case. 
The way it is in the original patch.

> Thanks,
> Durga
>
> > +
> > +exit:
> > +	return ref;
> > +}
> > +EXPORT_SYMBOL_GPL(thermal_zone_get_zone_by_name);
> > +
> >   #ifdef CONFIG_NET
> >   static struct genl_family thermal_event_genl_family = {
> >   	.id = GENL_ID_GENERATE,
> > diff --git a/include/linux/thermal.h b/include/linux/thermal.h
> > index 542a39c..0cf9eb5 100644
> > --- a/include/linux/thermal.h
> > +++ b/include/linux/thermal.h
> > @@ -237,6 +237,7 @@ void thermal_zone_device_update(struct
> > thermal_zone_device *);
> >   struct thermal_cooling_device *thermal_cooling_device_register(char *,
> > void *,
> >   		const struct thermal_cooling_device_ops *);
> >   void thermal_cooling_device_unregister(struct thermal_cooling_device *);
> > +struct thermal_zone_device *thermal_zone_get_zone_by_name(const
> > char *name);
> >
> >   int thermal_zone_trend_get(struct thermal_zone_device *, int);
> >   struct thermal_instance *thermal_instance_get(struct
> > thermal_zone_device *,
> > --
> > 1.7.7.1.488.ge8e1c

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