Date: Tue, 8 May 2012 13:16:37 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Amit Daniel Kachhap <amit.kachhap@linaro.org>
Cc: linux-pm@lists.linux-foundation.org, durgadoss.r@intel.com,
        linux-acpi@vger.kernel.org, lenb@kernel.org, rui.zhang@intel.com,
        linaro-dev@lists.linaro.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-samsung-soc@vger.kernel.org, patches@linaro.org
Subject: Re: [PATCH v3 5/6] thermal: exynos: Register the tmu sensor with
 the kernel thermal layer
Message-Id: <20120508131637.a2f59904.akpm@linux-foundation.org>
In-Reply-To: <1336493898-7039-6-git-send-email-amit.kachhap@linaro.org>
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	<1336493898-7039-4-git-send-email-amit.kachhap@linaro.org>
	<1336493898-7039-5-git-send-email-amit.kachhap@linaro.org>
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On Tue,  8 May 2012 21:48:17 +0530
Amit Daniel Kachhap <amit.kachhap@linaro.org> wrote:

> This code added creates a link between temperature sensors, linux thermal
> framework and cooling devices for samsung exynos platform. This layer
> monitors the temperature from the sensor and informs the generic thermal
> layer to take the necessary cooling action.
> 
>
> ...
>
> +static void exynos_report_trigger(void)
> +{
> +	unsigned int i;
> +	char data[2];
> +	char *envp[] = { data, NULL };
> +
> +	if (!th_zone || !th_zone->therm_dev)
> +		return;
> +
> +	thermal_zone_device_update(th_zone->therm_dev);
> +
> +	mutex_lock(&th_zone->therm_dev->lock);
> +	/* Find the level for which trip happened */
> +	for (i = 0; i < th_zone->sensor_conf->trip_data.trip_count; i++) {
> +		if (th_zone->therm_dev->last_temperature <
> +			th_zone->sensor_conf->trip_data.trip_val[i] * 1000)
> +			break;
> +	}
> +
> +	if (th_zone->mode == THERMAL_DEVICE_ENABLED) {
> +		if (i > 0)
> +			th_zone->therm_dev->polling_delay = ACTIVE_INTERVAL;
> +		else
> +			th_zone->therm_dev->polling_delay = IDLE_INTERVAL;
> +	}
> +
> +	sprintf(data, "%u", i);

yikes, if `i' exceeds 9, we have a stack scribble.  Please review this
and at least use snprintf(...  sizeof(data)) to prevent accidents.


> +	kobject_uevent_env(&th_zone->therm_dev->device.kobj, KOBJ_CHANGE, envp);
> +	mutex_unlock(&th_zone->therm_dev->lock);
> +}
> +
>
> ...
>
> +/* Get trip temperature callback functions for thermal zone */
> +static int exynos_get_trip_temp(struct thermal_zone_device *thermal, int trip,
> +				unsigned long *temp)
> +{
> +	if (trip < 0 || trip > 2)

I don't know what `trip' does and I don't know the meaning of the
values 0, 1 and 2.  Documentation, please.

> +		return -EINVAL;
> +
> +	*temp = th_zone->sensor_conf->trip_data.trip_val[trip];
> +	/* convert the temperature into millicelsius */
> +	*temp = *temp * 1000;
> +
> +	return 0;
> +}
> +
>
> ...
>
> +/* Bind callback functions for thermal zone */
> +static int exynos_bind(struct thermal_zone_device *thermal,
> +			struct thermal_cooling_device *cdev)
> +{
> +	int ret = 0;
> +
> +	/* if the cooling device is the one from exynos4 bind it */
> +	if (cdev != th_zone->cool_dev[0])
> +		return 0;
> +
> +	if (thermal_zone_bind_cooling_device(thermal, 0, cdev)) {
> +		pr_err("error binding cooling dev inst 0\n");
> +		return -EINVAL;
> +	}
> +	if (thermal_zone_bind_cooling_device(thermal, 1, cdev)) {
> +		pr_err("error binding cooling dev inst 1\n");
> +		ret = -EINVAL;
> +		goto error_bind1;
> +	}

There can never be more than two instances?

> +	return ret;
> +error_bind1:
> +	thermal_zone_unbind_cooling_device(thermal, 0, cdev);
> +	return ret;
> +}
> +
>
> ...
>
> +/* Get temperature callback functions for thermal zone */
> +static int exynos_get_temp(struct thermal_zone_device *thermal,
> +			unsigned long *temp)
> +{
> +	void *data;
> +
> +	if (!th_zone->sensor_conf) {
> +		pr_info("Temperature sensor not initialised\n");
> +		return -EINVAL;
> +	}
> +	data = th_zone->sensor_conf->private_data;
> +	*temp = th_zone->sensor_conf->read_temperature(data);
> +	/* convert the temperature into millicelsius */
> +	*temp = *temp * 1000;
> +	return 0;
> +}
> +
> +/* Operation callback functions for thermal zone */
> +static struct thermal_zone_device_ops exynos_dev_ops = {

Can it be const?  That sometimes saves space, as the table doesn't need
to be moved into writeable storage at runtime.

> +	.bind = exynos_bind,
> +	.unbind = exynos_unbind,
> +	.get_temp = exynos_get_temp,
> +	.get_mode = exynos_get_mode,
> +	.set_mode = exynos_set_mode,
> +	.get_trip_type = exynos_get_trip_type,
> +	.get_trip_temp = exynos_get_trip_temp,
> +	.get_crit_temp = exynos_get_crit_temp,
> +};
> +
> +/* Register with the in-kernel thermal management */
> +static int exynos_register_thermal(struct thermal_sensor_conf *sensor_conf)
> +{
> +	int ret, count, tab_size;
> +	struct freq_clip_table *tab_ptr;
> +
> +	if (!sensor_conf || !sensor_conf->read_temperature) {
> +		pr_err("Temperature sensor not initialised\n");
> +		return -EINVAL;
> +	}
> +
> +	th_zone = kzalloc(sizeof(struct exynos_thermal_zone), GFP_KERNEL);
> +	if (!th_zone) {
> +		ret = -ENOMEM;
> +		goto err_unregister;

This seems wrong?  If we need to call exynos_unregister_thermal() on
this error path then we needed to call it on the predecing one? 
Perhaps?

> +	}
> +
> +	th_zone->sensor_conf = sensor_conf;
> +
> +	tab_ptr = (struct freq_clip_table *)sensor_conf->cooling_data.freq_data;
> +	tab_size = sensor_conf->cooling_data.freq_clip_count;
> +
> +	/* Register the cpufreq cooling device */
> +	th_zone->cool_dev_size = 1;
> +	count = 0;
> +	th_zone->cool_dev[count] = cpufreq_cooling_register(
> +			(struct freq_clip_table *)&(tab_ptr[count]),
> +			tab_size, cpumask_of(0));
> +
> +	if (IS_ERR(th_zone->cool_dev[count])) {
> +		pr_err("Failed to register cpufreq cooling device\n");
> +		ret = -EINVAL;
> +		th_zone->cool_dev_size = 0;
> +		goto err_unregister;
> +	}
> +
> +	th_zone->therm_dev = thermal_zone_device_register(sensor_conf->name,
> +			3, NULL, &exynos_dev_ops, 0, 0, 0, IDLE_INTERVAL);
> +
> +	if (IS_ERR(th_zone->therm_dev)) {
> +		pr_err("Failed to register thermal zone device\n");
> +		ret = -EINVAL;
> +		goto err_unregister;
> +	}
> +	th_zone->mode = THERMAL_DEVICE_ENABLED;
> +
> +	pr_info("Exynos: Kernel Thermal management registered\n");
> +
> +	return 0;
> +
> +err_unregister:
> +	exynos_unregister_thermal();
> +	return ret;
> +}
> +
>
> ...
>

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