linux-kernel - Re: [PATCH] thermal/drivers/of: Add a get_temp

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Message-ID: <20190423154430.GA16014@localhost.localdomain>
Date:   Tue, 23 Apr 2019 08:44:31 -0700
From:   Eduardo Valentin <edubezval@...il.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     rui.zhang@...el.com, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, andrew.smirnov@...il.com
Subject: Re: [PATCH] thermal/drivers/of: Add a get_temp_id callback function

Hello,

On Tue, Apr 16, 2019 at 07:22:03PM +0200, Daniel Lezcano wrote:
> Currently when we register a sensor, we specify the sensor id and a data
> pointer to be passed when the get_temp function is called. However the
> sensor_id is not passed to the get_temp callback forcing the driver to
> do extra allocation and adding back pointer to find out from the sensor
> information the driver data and then back to the sensor id.
> 
> Add a new callback get_temp_id() which will be called if set. It will
> call the get_temp_id() with the sensor id.
> 
> That will be more consistent with the registering function.

I still do not understand why we need to have a get_id callback.
The use cases I have seen so far, which I have been intentionally rejecting, are
mainly solvable by creating other compatible entries. And really, if you
have, say a bandgap, chip that supports multiple sensors, but on
SoC version A it has 5 sensors, and on SoC version B it has only 4,
or on SoC version C, it has 5 but they are either logially located
in different places (gpu vs iva regions), these are all cases in which
you want a different compatible!

Do you mind sharing why you need a get sensor id callback?

> 
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> Tested-by: Andrey Smirnov <andrew.smirnov@...il.com>
> ---
>  drivers/thermal/of-thermal.c | 19 +++++++++++++------
>  include/linux/thermal.h      |  1 +
>  2 files changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/thermal/of-thermal.c b/drivers/thermal/of-thermal.c
> index 2df059cc07e2..787d1cbe13f3 100644
> --- a/drivers/thermal/of-thermal.c
> +++ b/drivers/thermal/of-thermal.c
> @@ -78,6 +78,8 @@ struct __thermal_zone {
>  
>  	/* sensor interface */
>  	void *sensor_data;
> +	int sensor_id;
> +
>  	const struct thermal_zone_of_device_ops *ops;
>  };
>  
> @@ -88,10 +90,14 @@ static int of_thermal_get_temp(struct thermal_zone_device *tz,
>  {
>  	struct __thermal_zone *data = tz->devdata;
>  
> -	if (!data->ops->get_temp)
> -		return -EINVAL;
> +	if (data->ops->get_temp)
> +		return data->ops->get_temp(data->sensor_data, temp);
>  
> -	return data->ops->get_temp(data->sensor_data, temp);
> +	if (data->ops->get_temp_id)
> +		return data->ops->get_temp_id(data->sensor_id,
> +					      data->sensor_data, temp);
> +
> +	return -EINVAL;
>  }
>  
>  static int of_thermal_set_trips(struct thermal_zone_device *tz,
> @@ -407,8 +413,8 @@ static struct thermal_zone_device_ops of_thermal_ops = {
>  /***   sensor API   ***/
>  
>  static struct thermal_zone_device *
> -thermal_zone_of_add_sensor(struct device_node *zone,
> -			   struct device_node *sensor, void *data,
> +thermal_zone_of_add_sensor(struct device_node *zone, struct device_node *sensor,
> +			   int sensor_id, void *data,
>  			   const struct thermal_zone_of_device_ops *ops)
>  {
>  	struct thermal_zone_device *tzd;
> @@ -426,6 +432,7 @@ thermal_zone_of_add_sensor(struct device_node *zone,
>  	mutex_lock(&tzd->lock);
>  	tz->ops = ops;
>  	tz->sensor_data = data;
> +	tz->sensor_id = sensor_id;
>  
>  	tzd->ops->get_temp = of_thermal_get_temp;
>  	tzd->ops->get_trend = of_thermal_get_trend;
> @@ -516,7 +523,7 @@ thermal_zone_of_sensor_register(struct device *dev, int sensor_id, void *data,
>  		}
>  
>  		if (sensor_specs.np == sensor_np && id == sensor_id) {
> -			tzd = thermal_zone_of_add_sensor(child, sensor_np,
> +			tzd = thermal_zone_of_add_sensor(child, sensor_np, sensor_id,
>  							 data, ops);
>  			if (!IS_ERR(tzd))
>  				tzd->ops->set_mode(tzd, THERMAL_DEVICE_ENABLED);
> diff --git a/include/linux/thermal.h b/include/linux/thermal.h
> index 5f4705f46c2f..2762d7e6dd86 100644
> --- a/include/linux/thermal.h
> +++ b/include/linux/thermal.h
> @@ -351,6 +351,7 @@ struct thermal_genl_event {
>   *		   hardware.
>   */
>  struct thermal_zone_of_device_ops {
> +	int (*get_temp_id)(int, void *, int *);
>  	int (*get_temp)(void *, int *);
>  	int (*get_trend)(void *, int, enum thermal_trend *);
>  	int (*set_trips)(void *, int, int);
> -- 
> 2.17.1
>