hwmon: (tmp421) support disabling channels from DT

The previous patch introduced per channel subnodes in DT that let us
specify some channel specific properties. This built a ground for easily
disabling individual channels of the sensor that may not be connected to
any external diode and thus are not returning any meaningful data.

This patch adds support for parsing the "status" property of channels DT
subnodes and makes sure the -ENODATA is returned when disabled channels
value is read.

Signed-off-by: Krzysztof Adamski <krzysztof.adamski@nokia.com>
Link: https://lore.kernel.org/r/a85d623f0792b862870933a875bdf802f4c017f1.1634206677.git.krzysztof.adamski@nokia.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

diff --git a/drivers/hwmon/tmp421.c b/drivers/hwmon/tmp421.c
index 89346ca6c9a907ca1060f467a252715556edca8c..af08bc985a130ff7bef26ad4805b68f1206d316a 100644 (file)
--- a/drivers/hwmon/tmp421.c
+++ b/drivers/hwmon/tmp421.c
@@ -89,6 +89,7 @@ MODULE_DEVICE_TABLE(of, tmp421_of_match);
 
 struct tmp421_channel {
        const char *label;
+       bool enabled;
        s16 temp;
 };
 
@@ -170,6 +171,9 @@ static int tmp421_read(struct device *dev, enum hwmon_sensor_types type,
        if (ret)
                return ret;
 
+       if (!tmp421->channel[channel].enabled)
+               return -ENODATA;
+
        switch (attr) {
        case hwmon_temp_input:
                *val = temp_from_raw(tmp421->channel[channel].temp,
@@ -323,6 +327,8 @@ static int tmp421_probe_child_from_dt(struct i2c_client *client,
        if (data->channel[i].label)
                data->temp_config[i] |= HWMON_T_LABEL;
 
+       data->channel[i].enabled = of_device_is_available(child);
+
        return 0;
 }
 
@@ -371,8 +377,10 @@ static int tmp421_probe(struct i2c_client *client)
        if (err)
                return err;
 
-       for (i = 0; i < data->channels; i++)
+       for (i = 0; i < data->channels; i++) {
                data->temp_config[i] = HWMON_T_INPUT | HWMON_T_FAULT;
+               data->channel[i].enabled = true;
+       }
 
        err = tmp421_probe_from_dt(client, data);
        if (err)