Re: [RFC 2/2] hwmon: lm90: add thermal_zone temperature sensor support

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On 02/05/2017 01:03 PM, Christian Lamparter wrote:
This patch adds thermal_zone temperature sensor support
to the lm90 module. The feature has to be enabled
separately via the Kconfig option:
	CONFIG_SENSORS_LM90_THERMAL_DEVICE

The LM90 supports two (three for MAX6695 and MAX6696)
temperature sensors. The local sensor is integrated
into the LM90 chip. The remote sensors are connected
to external temperature sensing diodes.

Cc: Wei Ni <wni@xxxxxxxxxx>
Signed-off-by: Christian Lamparter <chunkeey@xxxxxxxxxxxxxx>

Since the hwnmon core now supports thermal registration, and since the lm90
driver has already been converted to using the new hwmon API, I would
rather like to understand why using the hwmon core for this purpose is
insufficient, and I would prefer to address the deficiencies in the hwmon
core and not in the driver.

Thanks,
Guenter

---
---
 drivers/hwmon/Kconfig | 11 +++++++
 drivers/hwmon/lm90.c  | 91 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 102 insertions(+)

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 190d270b20a2..9df70ad21a21 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1085,6 +1085,17 @@ config SENSORS_LM90
 	  This driver can also be built as a module.  If so, the module
 	  will be called lm90.

+config SENSORS_LM90_THERMAL_DEVICE
+	bool "Support for thermal-zone temperature sensors"
+	depends on SENSORS_LM90 && THERMAL_OF
+	help
+	  If you say yes here you get support for thermal-zone temperature
+	  sensors for the lm90 module and all supported chips.
+
+	  Refer to Documentation/devicetree/bindings/thermal/thermal.txt
+	  and Documentation/devicetree/bindings/hwmon/lm90.txt on how to
+	  use it for your platform.
+
 config SENSORS_LM92
 	tristate "National Semiconductor LM92 and compatibles"
 	depends on I2C
diff --git a/drivers/hwmon/lm90.c b/drivers/hwmon/lm90.c
index 841f2428e84a..584550c7336d 100644
--- a/drivers/hwmon/lm90.c
+++ b/drivers/hwmon/lm90.c
@@ -95,6 +95,9 @@
 #include <linux/sysfs.h>
 #include <linux/interrupt.h>
 #include <linux/regulator/consumer.h>
+#include <linux/of.h>
+#include <linux/thermal.h>
+#include <dt-bindings/thermal/lm90.h>

 /*
  * Addresses to scan
@@ -1643,6 +1646,90 @@ static const struct hwmon_ops lm90_ops = {
 	.write = lm90_write,
 };

+#ifdef CONFIG_SENSORS_LM90_THERMAL_DEVICE
+
+static int lm90_read_local_temp(void *data, int *temp)
+{
+	*temp = lm90_get_temp11(data, LOCAL_TEMP);
+	return 0;
+}
+
+static int lm90_read_remote_temp(void *data, int *temp)
+{
+	*temp = lm90_get_temp11(data, REMOTE_TEMP);
+	return 0;
+}
+
+static int lm90_read_remote2_temp(void *data, int *temp)
+{
+	*temp = lm90_get_temp11(data, REMOTE2_TEMP);
+	return 0;
+}
+
+static const struct thermal_zone_of_device_ops local_temp_sensor = {
+	.get_temp = lm90_read_local_temp,
+};
+
+static const struct thermal_zone_of_device_ops remote_temp_sensor = {
+	.get_temp = lm90_read_remote_temp,
+};
+
+static const struct thermal_zone_of_device_ops remote2_temp_sensor = {
+	.get_temp = lm90_read_remote2_temp,
+};
+
+static const struct thermal_zone_sensors_struct {
+	int sensor_id;
+	const char *name;
+	const struct thermal_zone_of_device_ops *ops;
+	u32 flag_mask;
+	u32 flag_required;
+} thermal_zone_sensors[] = {
+	{ LM90_REMOTE_TEMPERATURE, "remote", &remote_temp_sensor },
+	{ LM90_LOCAL_TEMPERATURE, "local", &local_temp_sensor },
+	{ LM90_REMOTE2_TEMPERATURE, "second remote", &remote2_temp_sensor,
+	  LM90_HAVE_TEMP3, LM90_HAVE_TEMP3 },
+};
+
+static int lm90_setup_thermal_device(struct device *dev,
+				     struct lm90_data *data)
+{
+	const struct thermal_zone_sensors_struct *entry;
+	struct thermal_zone_device *therm_dev;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(thermal_zone_sensors); i++) {
+		entry = &thermal_zone_sensors[i];
+
+		if ((data->flags & entry->flag_mask) != entry->flag_required)
+			continue;
+
+		therm_dev = devm_thermal_zone_of_sensor_register(dev,
+			entry->sensor_id, data, entry->ops);
+
+		/*
+		 * if a sensor device isn't requested in a thermal-zone the
+		 * call to devm_thermal_zone_of_sensor_register will fail
+		 * with -ENODEV. In this case we can ignore/skip it.
+		 */
+
+		if (IS_ERR(therm_dev) && (PTR_ERR(therm_dev) != -ENODEV)) {
+			dev_err(dev, "Failed to register %s thermal_zone sensor device\n",
+				entry->name);
+			return PTR_ERR(therm_dev);
+		}
+	}
+	return 0;
+}
+#else
+static int lm90_setup_thermal_device(struct device __maybe_unused *dev,
+				     struct lm90_data __maybe_unused *data)
+{
+	return 0;
+}
+#endif
+
+
 static int lm90_probe(struct i2c_client *client,
 		      const struct i2c_device_id *id)
 {
@@ -1765,6 +1852,10 @@ static int lm90_probe(struct i2c_client *client,
 	if (IS_ERR(hwmon_dev))
 		return PTR_ERR(hwmon_dev);

+	err = lm90_setup_thermal_device(dev, data);
+	if (err)
+		return err;
+
 	if (client->irq) {
 		dev_dbg(dev, "IRQ: %d\n", client->irq);
 		err = devm_request_threaded_irq(dev, client->irq,


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