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Message-ID: <CAJZ5v0hzS-bquhW_wbsd81EpJYx5RHxeXkamdZ+MBs4oczDw1A@mail.gmail.com>
Date: Thu, 7 Oct 2021 18:38:22 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Alexandre Bailon <abailon@...libre.com>
Cc: "Zhang, Rui" <rui.zhang@...el.com>,
Daniel Lezcano <daniel.lezcano@...aro.org>,
Amit Kucheria <amitk@...nel.org>,
Linux PM <linux-pm@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
ben.tseng@...iatek.com, Kevin Hilman <khilman@...libre.com>,
Matthias Kaehlcke <mka@...omium.org>,
kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v2 2/2] thermal: add a virtual sensor to aggregate temperatures
On Fri, Sep 17, 2021 at 9:25 AM Alexandre Bailon <abailon@...libre.com> wrote:
>
> This adds a virtual thermal sensor that reads temperature from
This should be "virtual sensor driver" I suppose.
> hardware sensor and return an aggregated temperature.
"returns"
Also wrapping it around a single hardware sensor makes a little sense
AFAICS, so I guess you mean "multiple hardware sensors" here.
> Currently, this supports three operations:
> the minimum, maximum and average temperature.
They are aggregation functions rather than "operations"
>
> Reported-by: kernel test robot <lkp@...el.com>
This is new code, so what does it fix?
> Signed-off-by: Alexandre Bailon <abailon@...libre.com>
> ---
> drivers/thermal/Kconfig | 8 +
> drivers/thermal/Makefile | 1 +
> drivers/thermal/virtual-thermal-sensor.h | 54 ++++
> drivers/thermal/virtual_thermal_sensor.c | 350 +++++++++++++++++++++++
> 4 files changed, 413 insertions(+)
> create mode 100644 drivers/thermal/virtual-thermal-sensor.h
> create mode 100644 drivers/thermal/virtual_thermal_sensor.c
>
> diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
> index d7f44deab5b1d..20bc93c48f5b1 100644
> --- a/drivers/thermal/Kconfig
> +++ b/drivers/thermal/Kconfig
> @@ -228,6 +228,14 @@ config THERMAL_MMIO
> register or shared memory, is a potential candidate to work with this
> driver.
>
> +config VIRTUAL_THERMAL
> + tristate "Virtual thermal sensor driver"
This should be "DT-based virtual thermal sensor driver" I think.
> + depends on THERMAL_OF || COMPILE_TEST
> + help
> + This option enables the generic thermal sensor aggregator.
"generic DT-based"
> + This driver creates a thermal sensor that reads the hardware sensors
s/the/multiple/
> + and aggregate the temperature.
"aggregates their output"
> +
> config HISI_THERMAL
> tristate "Hisilicon thermal driver"
> depends on ARCH_HISI || COMPILE_TEST
> diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
> index 82fc3e616e54b..8bf55973059c5 100644
> --- a/drivers/thermal/Makefile
> +++ b/drivers/thermal/Makefile
> @@ -60,3 +60,4 @@ obj-$(CONFIG_UNIPHIER_THERMAL) += uniphier_thermal.o
> obj-$(CONFIG_AMLOGIC_THERMAL) += amlogic_thermal.o
> obj-$(CONFIG_SPRD_THERMAL) += sprd_thermal.o
> obj-$(CONFIG_KHADAS_MCU_FAN_THERMAL) += khadas_mcu_fan.o
> +obj-$(CONFIG_VIRTUAL_THERMAL) += virtual_thermal_sensor.o
> diff --git a/drivers/thermal/virtual-thermal-sensor.h b/drivers/thermal/virtual-thermal-sensor.h
> new file mode 100644
> index 0000000000000..3bbf7c324dddc
> --- /dev/null
> +++ b/drivers/thermal/virtual-thermal-sensor.h
> @@ -0,0 +1,54 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (c) 2021 BayLibre
> + */
> +
> +#ifndef __THERMAL_VIRTUAL_SENSOR_H__
> +#define __THERMAL_VIRTUAL_SENSOR_H__
> +
> +#include <linux/device.h>
> +#include <linux/thermal.h>
> +
> +struct virtual_thermal_sensor;
> +struct thermal_sensor_data;
> +
> +#if IS_ENABLED(CONFIG_VIRTUAL_THERMAL)
> +struct thermal_sensor_data *
> +thermal_virtual_sensor_register(struct device *dev, int sensor_id, void *data,
> + const struct thermal_zone_of_device_ops *ops);
> +void thermal_virtual_sensor_unregister(struct device *dev,
> + struct thermal_sensor_data *sensor_data);
> +struct thermal_sensor_data *
> +devm_thermal_virtual_sensor_register(struct device *dev, int sensor_id, void *data,
> + const struct thermal_zone_of_device_ops *ops);
> +
> +void devm_thermal_virtual_sensor_unregister(struct device *dev,
> + struct virtual_thermal_sensor *sensor);
> +#else
> +static inline struct thermal_sensor_data *
> +thermal_virtual_sensor_register(struct device *dev, int sensor_id, void *data,
> + const struct thermal_zone_of_device_ops *ops)
> +{
> + return ERR_PTR(-ENODEV);
> +}
> +
> +void thermal_virtual_sensor_unregister(struct device *dev,
> + struct thermal_sensor_data *sensor_data)
> +{
> +}
> +
> +static inline struct thermal_sensor_data *
> +devm_thermal_virtual_sensor_register(struct device *dev, int sensor_id, void *data,
> + const struct thermal_zone_of_device_ops *ops)
> +{
> + return ERR_PTR(-ENODEV);
> +}
> +
> +static inline
> +void devm_thermal_virtual_sensor_unregister(struct device *dev,
> + struct virtual_thermal_sensor *sensor)
> +{
> +}
> +#endif
> +
> +#endif /* __THERMAL_VIRTUAL_SENSOR_H__ */
> diff --git a/drivers/thermal/virtual_thermal_sensor.c b/drivers/thermal/virtual_thermal_sensor.c
> new file mode 100644
> index 0000000000000..234563af6643e
> --- /dev/null
> +++ b/drivers/thermal/virtual_thermal_sensor.c
> @@ -0,0 +1,350 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2021 BayLibre
Please add information on what's in this file to the preamble.
> + */
> +
> +#include <linux/err.h>
> +#include <linux/export.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +#include <linux/of_platform.h>
> +#include <linux/slab.h>
> +#include <linux/thermal.h>
> +#include <linux/types.h>
> +#include <linux/string.h>
> +
> +#include <dt-bindings/thermal/virtual-sensor.h>
> +
> +#include "virtual-thermal-sensor.h"
> +
> +struct thermal_sensor_data {
> + struct list_head node;
> +
> + /* sensor interface */
> + int id;
> + void *sensor_data;
> + const struct thermal_zone_of_device_ops *ops;
> +};
> +
> +struct virtual_thermal_sensor {
> + int count;
> + struct thermal_sensor_data *sensors;
> + struct thermal_zone_device *tzd;
> + int (*aggr_temp)(int temp1, int temp2);
> +
> + struct list_head node;
> +};
> +
> +static LIST_HEAD(thermal_sensors);
> +static LIST_HEAD(virtual_sensors);
These lists don't seem to be protected against concurrent access and
they should be.
> +
> +static int max_temp(int temp1, int temp2)
> +{
> + return max(temp1, temp2);
> +}
> +
> +static int min_temp(int temp1, int temp2)
> +{
> + return min(temp1, temp2);
> +}
> +
> +static int avg_temp(int temp1, int temp2)
> +{
> + return ((temp1) / 2) + ((temp2) / 2) + (((temp1) % 2 + (temp2) % 2) / 2);
There are a few redundant parens here.
And why not
return (temp1 + temp2) / 2;
> +}
> +
> +static int virtual_thermal_sensor_get_temp(void *data, int *temperature)
> +{
> + struct virtual_thermal_sensor *sensor = data;
> + int max_temp = INT_MIN;
> + int temp;
> + int i;
> +
Some synchronization (eg. locking) should be added to this. It is racy as is.
> + for (i = 0; i < sensor->count; i++) {
> + struct thermal_sensor_data *hw_sensor;
> +
> + hw_sensor = &sensor->sensors[i];
> + if (!hw_sensor->ops)
> + return -ENODEV;
> +
> + hw_sensor->ops->get_temp(hw_sensor->sensor_data, &temp);
> + max_temp = sensor->aggr_temp(max_temp, temp);
> + }
> +
> + *temperature = max_temp;
> +
> + return 0;
> +}
> +
> +static const struct thermal_zone_of_device_ops virtual_thermal_sensor_ops = {
> + .get_temp = virtual_thermal_sensor_get_temp,
> +};
> +
> +static int virtual_sensor_add_sensor(struct virtual_thermal_sensor *sensor,
> + struct of_phandle_args args,
> + int index)
> +{
> + struct thermal_sensor_data *sensor_data;
> + int id;
> +
> + list_for_each_entry(sensor_data, &thermal_sensors, node) {
> + id = args.args_count ? args.args[0] : 0;
> + if (sensor_data->id == id) {
> + memcpy(&sensor->sensors[index], sensor_data,
> + sizeof(*sensor_data));
The data object being copied includes pointers, so I wouldn't copy
them like this. Especially the ops one annotated as const.
> + return 0;
> + }
> + }
> +
> + return -ENODEV;
> +}
> +
> +static int virtual_thermal_sensor_probe(struct platform_device *pdev)
> +{
> + struct virtual_thermal_sensor *sensor;
> + struct device *dev = &pdev->dev;
> + struct of_phandle_args args;
> + u32 type;
> + int ret;
> + int i;
> +
> + sensor = devm_kzalloc(dev, sizeof(*sensor), GFP_KERNEL);
> + if (!sensor)
> + return -ENOMEM;
> +
> + sensor->count = of_count_phandle_with_args(dev->of_node,
> + "thermal-sensors",
> + "#thermal-sensor-cells");
> + if (sensor->count <= 0)
> + return -EINVAL;
> +
> + sensor->sensors = devm_kmalloc_array(dev, sensor->count,
> + sizeof(*sensor->sensors),
> + GFP_KERNEL);
> + if (!sensor->sensors)
> + return -ENOMEM;
> +
> + for (i = 0; i < sensor->count; i++) {
> + ret = of_parse_phandle_with_args(dev->of_node,
> + "thermal-sensors",
> + "#thermal-sensor-cells",
> + i,
> + &args);
> + if (ret)
> + return ret;
> +
> + ret = virtual_sensor_add_sensor(sensor, args, i);
> + if (ret)
> + return ret;
> + }
> +
> + ret = of_property_read_u32(dev->of_node, "aggregation-function", &type);
> + if (ret)
> + return ret;
> +
> + switch (type) {
> + case VIRTUAL_THERMAL_SENSOR_MAX:
> + sensor->aggr_temp = max_temp;
> + break;
> + case VIRTUAL_THERMAL_SENSOR_MIN:
> + sensor->aggr_temp = min_temp;
> + break;
> + case VIRTUAL_THERMAL_SENSOR_AVG:
> + sensor->aggr_temp = avg_temp;
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + sensor->tzd = devm_thermal_zone_of_sensor_register(dev, 0, sensor,
> + &virtual_thermal_sensor_ops);
> + if (IS_ERR(sensor->tzd))
> + return PTR_ERR(sensor->tzd);
> +
> + platform_set_drvdata(pdev, sensor);
> + list_add(&sensor->node, &virtual_sensors);
> +
> + return 0;
> +}
> +
> +static int virtual_thermal_sensor_remove(struct platform_device *pdev)
> +{
> + struct virtual_thermal_sensor *sensor;
> +
> + sensor = platform_get_drvdata(pdev);
> + list_del(&sensor->node);
> +
> + return 0;
> +}
> +
> +static const struct of_device_id virtual_thermal_sensor_of_match[] = {
> + {
> + .compatible = "virtual,thermal-sensor",
> + },
> + {
> + },
> +};
> +MODULE_DEVICE_TABLE(of, virtual_thermal_sensor_of_match);
> +
> +static struct platform_driver virtual_thermal_sensor = {
> + .probe = virtual_thermal_sensor_probe,
> + .remove = virtual_thermal_sensor_remove,
> + .driver = {
> + .name = "virtual-thermal-sensor",
> + .of_match_table = virtual_thermal_sensor_of_match,
> + },
> +};
> +
> +/**
> + * thermal_virtual_sensor_register - registers a sensor that could be a virtual
> + * sensor
> + * @dev: a valid struct device pointer of a sensor device. Must contain
> + * a valid .of_node, for the sensor node.
> + * @sensor_id: a sensor identifier, in case the sensor IP has more
> + * than one sensor
> + * @data: a private pointer (owned by the caller) that will be passed
> + * back, when a temperature reading is needed.
> + * @ops: struct thermal_zone_of_device_ops *. Must contain at least .get_temp.
> + *
> + * This function will register a thermal sensor to make it available for later
> + * usage by a virtual sensor.
So who's expected to be calling it?
> + *
> + * The thermal zone temperature is provided by the @get_temp function
> + * pointer. When called, it will have the private pointer @data back.
It is unclear what you mean here. I think you are describing a return
mechanism, but as is it is hard to follow.
> + *
> + * Return: On success returns a valid struct thermal_zone_device,
That doesn't seem to be the case. It returns an address returned by
devm_kzalloc() and the memory at that address is expected to be a
thermal_sensor_data object.
> + * otherwise, it returns a corresponding ERR_PTR(). Caller must
> + * check the return value with help of IS_ERR() helper.
> + */
> +struct thermal_sensor_data *thermal_virtual_sensor_register(
> + struct device *dev, int sensor_id, void *data,
> + const struct thermal_zone_of_device_ops *ops)
> +{
> + struct thermal_sensor_data *sensor_data;
> +
> + sensor_data = devm_kzalloc(dev, sizeof(*sensor_data), GFP_KERNEL);
> + if (!sensor_data)
> + return ERR_PTR(-ENOMEM);
> +
> + sensor_data->id = sensor_id;
> + sensor_data->sensor_data = data;
> + sensor_data->ops = ops;
> +
> + list_add(&sensor_data->node, &thermal_sensors);
> +
> + return sensor_data;
Overall, this is non-modular code squeezed into a module.
If this module goes away and whoever called it wants to unregister the
sensor, they will crash, so to a minimum it should do a
try_module_get() on the module containing it.
> +}
> +EXPORT_SYMBOL_GPL(thermal_virtual_sensor_register);
> +
> +/**
> + * thermal_virtual_sensor_unregister - unregisters a sensor
> + * @dev: a valid struct device pointer of a sensor device.
> + * @sensor_data: a pointer to struct thermal_sensor_data to unregister.
> + *
> + * This function removes the sensor from the list of available thermal sensors.
> + * If the sensor is in use, then the next call to .get_temp will return -ENODEV.
> + */
> +void thermal_virtual_sensor_unregister(struct device *dev,
> + struct thermal_sensor_data *sensor_data)
> +{
> + struct thermal_sensor_data *sd;
> + struct virtual_thermal_sensor *sensor;
> + int i;
> +
All of the code in this function is obviously racy.
> + list_del(&sensor_data->node);
> +
> + list_for_each_entry(sensor, &virtual_sensors, node) {
> + for (i = 0; i < sensor->count; i++) {
> + sd = &sensor->sensors[i];
> + if (sd->id == sensor_data->id &&
> + sd->sensor_data == sensor_data->sensor_data) {
> + sd->ops = NULL;
> + }
The inner braces are not necessary.
> + }
> + }
And again, this code requires the module to be protected from
unloading until the last instance of
thermal_virtual_sensor_unregister() has returned.
> +}
> +EXPORT_SYMBOL_GPL(thermal_virtual_sensor_unregister);
> +
> +static void devm_thermal_virtual_sensor_release(struct device *dev, void *res)
> +{
> + thermal_virtual_sensor_unregister(dev,
> + *(struct thermal_sensor_data **)res);
> +}
> +
> +static int devm_thermal_virtual_sensor_match(struct device *dev, void *res,
> + void *data)
> +{
> + struct thermal_sensor_data **r = res;
> +
> + if (WARN_ON(!r || !*r))
> + return 0;
> +
> + return *r == data;
> +}
> +
> +/**
> + * devm_thermal_virtual_sensor_register - Resource managed version of
> + * thermal_virtual_sensor_register()
> + * @dev: a valid struct device pointer of a sensor device. Must contain
> + * a valid .of_node, for the sensor node.
> + * @sensor_id: a sensor identifier, in case the sensor IP has more
> + * than one sensor
> + * @data: a private pointer (owned by the caller) that will be passed
> + * back, when a temperature reading is needed.
> + * @ops: struct thermal_zone_of_device_ops *. Must contain at least .get_temp.
> + *
> + * Refer thermal_zone_of_sensor_register() for more details.
> + *
> + * Return: On success returns a valid struct virtual_sensor_data,
> + * otherwise, it returns a corresponding ERR_PTR(). Caller must
> + * check the return value with help of IS_ERR() helper.
> + * Registered virtual_sensor_data device will automatically be
> + * released when device is unbound.
> + */
> +struct thermal_sensor_data *devm_thermal_virtual_sensor_register(
> + struct device *dev, int sensor_id,
> + void *data, const struct thermal_zone_of_device_ops *ops)
> +{
> + struct thermal_sensor_data **ptr, *sensor_data;
> +
> + ptr = devres_alloc(devm_thermal_virtual_sensor_release, sizeof(*ptr),
> + GFP_KERNEL);
> + if (!ptr)
> + return ERR_PTR(-ENOMEM);
> +
> + sensor_data = thermal_virtual_sensor_register(dev, sensor_id, data, ops);
> + if (IS_ERR(sensor_data)) {
> + devres_free(ptr);
> + return sensor_data;
> + }
> +
> + *ptr = sensor_data;
> + devres_add(dev, ptr);
> +
> + return sensor_data;
> +}
> +EXPORT_SYMBOL_GPL(devm_thermal_virtual_sensor_register);
> +
> +/**
> + * devm_thermal_virtual_sensor_unregister - Resource managed version of
> + * thermal_virtual_sensor_unregister().
> + * @dev: Device for which resource was allocated.
> + * @sensor: a pointer to struct thermal_zone_device where the sensor is registered.
> + *
> + * This function removes the sensor from the list of sensors registered with
> + * devm_thermal_virtual_sensor_register() API.
> + * Normally this function will not need to be called and the resource
> + * management code will ensure that the resource is freed.
> + */
> +void devm_thermal_virtual_sensor_unregister(struct device *dev,
> + struct virtual_thermal_sensor *sensor)
> +{
> + WARN_ON(devres_release(dev, devm_thermal_virtual_sensor_release,
> + devm_thermal_virtual_sensor_match, sensor));
> +}
> +EXPORT_SYMBOL_GPL(devm_thermal_virtual_sensor_unregister);
> +
> +module_platform_driver(virtual_thermal_sensor);
> +MODULE_AUTHOR("Alexandre Bailon <abailon@...libre.com>");
> +MODULE_DESCRIPTION("Virtual thermal sensor");
> +MODULE_LICENSE("GPL v2");
> --
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