Subject: [RFC PATCH 5/9] Thermal: Support using dt node to get sensor

From: [email-masked] (Wei Ni)
Date: Wed, 20 Feb 2013 18:36:00 +0800

On 02/20/2013 07:12 AM, Stephen Warren wrote:
> On 02/18/2013 04:30 AM, Wei Ni wrote:
>> Add functions to support using dt node with args to get sensor.
> 
> You need to write a device tree binding document to explain this.
> 
>> diff --git a/drivers/thermal/thermal_sys.c b/drivers/thermal/thermal_sys.c
> 
>> +struct thermal_sensor *get_sensor_by_node(struct node_args *np_args)
>> +{
>> +	struct thermal_sensor *pos;
> 
> "pos" isn't a great variable name. Why not use "sensor", or just the
> "ts" variable you have right below?

Oh, yes, it can just use "ts" simply. I didn't consider it, thanks.

> 
>> +	struct thermal_sensor *ts = NULL;
>> +	struct node_args *args;
>> +
>> +	mutex_lock(&sensor_list_lock);
>> +	for_each_thermal_sensor(pos) {
>> +		args = &pos->np_args;
>> +		if (args->np) {
>> +			if ((args->np == np_args->np) &&
>> +			   (args->index == np_args->index)) {
>> +				ts = pos;
>> +				break;
> 
> Replace those 2 lines with "goto out;".
> 
>> +			}
>> +		}
>> +	}
> 
> here, add:
> 
> 	ts = NULL;
> out:
> 
> That way, you can use "ts" as the loop iteration variable.
> 
> This whole patch rather assumes that all DT nodes can identify their
> exposed thermal sensors using an index in a single DT cell. That's not
> very flexible. All other DT bindings work like this:
> 
> Provider of a service indicates how many DT cells are in the object
> (GPIO, IRQ, thermal sensors) specifier:
> 
> sensor1: lm90 at 1c {
> 	...
> 	#thermal-sensor-cells = <1>;
> };
> 
> Each consumer of a service imports it by referencing it:
> 
> thermal-zone {
> 	...
> 	sensors = <&sensor1 0>;
> };
> 
> The driver for LM90 provides an "of_xlate" function which receives a
> struct of_phandle_args and outputs/returns whatever Linux-internal
> identification/representation of the object is required. For example, see:
> 
>> include/linux/pwm.h:161:	struct pwm_device *	(*of_xlate)(struct pwm_chip *pc,
> 
> This allows each providing object's DT binding to define its own value
> of #thermal-sensor-cells, as suited for its own requirements, and allows
> each driver to implement the mapping from DT to internal ID in whatever
> way is necessary.
> 
> Now, many bindings/drivers might just end up using a common simple
> implementation. That's why functions such as of_pwm_simple_xlate() or
> of_gpio_simple_xlate() exist.

It looks like the "of_xlate" can handle the sensor identification.
I'm not familiar with this function, I will look into it and try to use.
Thanks for your comments.

Wei.