linux-kernel - Re: [PATCHv3 02/16] drivers: thermal: introduce device tree parser

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Date:	Wed, 18 Sep 2013 15:44:16 -0400
From:	Eduardo Valentin <eduardo.valentin@...com>
To:	Joe Perches <joe@...ches.com>
CC:	Eduardo Valentin <eduardo.valentin@...com>,
	<swarren@...dotorg.org>, <pawel.moll@....com>,
	<mark.rutland@....com>, <ian.campbell@...rix.com>,
	<rob.herring@...xeda.com>, <linux@...ck-us.net>,
	<rui.zhang@...el.com>, <wni@...dia.com>, <grant.likely@...aro.org>,
	<durgadoss.r@...el.com>, <linux-pm@...r.kernel.org>,
	<devicetree@...r.kernel.org>, <lm-sensors@...sensors.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv3 02/16] drivers: thermal: introduce device tree parser

Hello Joe,

Thanks for reviewing this code. Couple of replies.

 18-09-2013 15:11, Joe Perches wrote:
> On Wed, 2013-09-18 at 15:02 -0400, Eduardo Valentin wrote:
>> This patch introduces a device tree bindings for
>> describing the hardware thermal behavior and limits.
>> Also a parser to read and interpret the data and feed
>> it in the thermal framework is presented.
> 
> trivial notes:


No issues.

> 
>> diff --git a/drivers/thermal/of-thermal.c b/drivers/thermal/of-thermal.c
> []
>> +static int of_thermal_get_trend(struct thermal_zone_device *tz, int trip,
>> +				enum thermal_trend *trend)
>> +{
>> +	struct __thermal_zone *data = tz->devdata;
>> +	long dev_trend;
>> +	int r;
>> +
>> +	if (!data->get_trend)
>> +		return -EINVAL;
>> +
>> +	r = data->get_trend(data->sensor_data, &dev_trend);
>> +	if (r)
>> +		return r;
>> +
>> +	if (dev_trend > 0)
>> +		*trend = THERMAL_TREND_RAISING;
>> +	else if (dev_trend < 0)
>> +		*trend = THERMAL_TREND_DROPPING;
>> +	else
>> +		*trend = THERMAL_TREND_STABLE;
>> +
>> +	return 0;
>> +}
> 
> If readings are within some non zero noise level,
> perhaps stable should be returned.

Yes, there should be some sort of threshold for temperature trend. But I
am not sure this is the right place to implement this. This type of
feature is in my TODO list, but I am planing to get it done within the
core code of the thermal framework.


> 
>> +static struct __thermal_zone *
>> +thermal_of_build_thermal_zone(struct device_node *np)
>> +{
>> +	struct device_node *child, *gchild;
>> +	struct __thermal_zone *tz;
>> +	int ret, i;
>> +	u32 prop;
>> +
>> +	if (!np) {
>> +		pr_err("no thermal zone np\n");
>> +		return ERR_PTR(-EINVAL);
>> +	}
>> +
>> +	tz = kzalloc(sizeof(*tz), GFP_KERNEL);
>> +	if (!tz) {
>> +		pr_err("not enough memory for thermal of zone\n");
> 
> Unnecessary OOM message.
> All allocs without GFP_NOWARN get a dump_stack()
> 
>> +int __init of_parse_thermal_zones(void)
>> +{
> []
>> +		ops = kzalloc(sizeof(*ops), GFP_KERNEL);
>> +		if (!ops) {
>> +			pr_err("no memory available for thermal ops\n");
>> +			return 0;
>> +		}
>> +		memcpy(ops, &of_thermal_ops, sizeof(*ops));
>> +
>> +		tzp = kzalloc(sizeof(*tzp), GFP_KERNEL);
>> +		if (!ops) {
>> +			pr_err("no memory available for thermal zone params\n");
>> +			return 0;
>> +		}
> 
> a couple more OOMs.
> 

Hmmm.. I am pretty sure you have a good point. But to me seams to be
still a common practice to have drivers outputing error messages when
allocation fails. A simple git grep -A 4 kzalloc for instance, shows
that there are still quite a considerable amount of occurrences of such
practice.


> 
> 
> 


-- 
You have got to be excited about what you are doing. (L. Lamport)

Eduardo Valentin


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