linux-kernel - Re: [PATCHv2 1/3] thermal: introduce thermal_zone_get_zone_by

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Date:	Thu, 4 Apr 2013 16:22:16 -0400
From:	Eduardo Valentin <eduardo.valentin@...com>
To:	"R, Durgadoss" <durgadoss.r@...el.com>
CC:	Eduardo Valentin <eduardo.valentin@...com>,
	"Zhang, Rui" <rui.zhang@...el.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv2 1/3] thermal: introduce thermal_zone_get_zone_by_name
 helper function

On 04-04-2013 13:12, R, Durgadoss wrote:
>> -----Original Message-----
>> From: Eduardo Valentin [mailto:eduardo.valentin@...com]
>> Sent: Thursday, April 04, 2013 3:43 AM
>> To: Zhang, Rui
>> Cc: linux-pm@...r.kernel.org; linux-kernel@...r.kernel.org; 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@...com>
>> ---
>>   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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