Hi Rafael,

On 10/7/21 6:38 PM, Rafael J. Wysocki wrote:

On Fri, Sep 17, 2021 at 9:25 AM Alexandre Bailon [off-list ref] wrote:

quoted

This adds a virtual thermal sensor that reads temperature from

This should be "virtual sensor driver" I suppose.

quoted

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.

quoted

Currently, this supports three operations:
the minimum, maximum and average temperature.

They are aggregation functions rather than "operations"

quoted

Reported-by: kernel test robot <redacted>

This is new code, so what does it fix?

The CI has found some build issues.
I was not sure if I had to add this or not.

quoted

Signed-off-by: Alexandre Bailon <redacted>
---
  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.

quoted

+       depends on THERMAL_OF || COMPILE_TEST
+       help
+         This option enables the generic thermal sensor aggregator.

"generic DT-based"

quoted

+         This driver creates a thermal sensor that reads the hardware sensors

s/the/multiple/

quoted

+         and aggregate the temperature.

"aggregates their output"

quoted

+
  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.

Does something like "DT-based virtual thermal sensor driver" would be 
enough,
or should I details a little bit more ?

quoted

+ */
+
+#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.

I Reworked the driver and I am going to remove them.

quoted

+
+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;

quoted

+}
+
+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.

I am not sure to figure out what is racy here.
Anyway, I will update the logic of the driver and simplify this 
function, so this would
probably be fixed.

quoted

+       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.

quoted

+                       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?

Any driver that would like to expose its sensors to the virtual thermal 
sensor driver,
which was a bad solution ...
In the next series, I will remove this function, as well the other 
register /  unregister
functions, and use directly thermal_zone_device to get the temperature 
from the sensors.

Probe will take care of finding the thermal_zone_device listed in the 
virtual sensor device
tree node, will defer if a thermal_zone_device is not yet ready and use 
try_module_get()
to prevent any thermal_zone_device used by the virtual sensor to be removed.

Best Regards,
Alexandre

quoted

+ *
+ * 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.

quoted

+ *
+ * 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.

quoted

+ * 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.

quoted

+}
+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.

quoted

+       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.

quoted

+               }
+       }

And again, this code requires the module to be protected from
unloading until the last instance of
thermal_virtual_sensor_unregister() has returned.

quoted

+}
+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 [off-list ref]");
+MODULE_DESCRIPTION("Virtual thermal sensor");
+MODULE_LICENSE("GPL v2");
--