The thermal core uses the existence of the .get_temp, .get_trend and
.set_emul_temp to detect whether this operation exists and should be
used or whether it should be emulated in software. This makes problems
for of-thermal which has to modify the struct thermal_zone_device_ops
during runtime whenever a sensor is registered or unregistered.

Let the core test for -ENOSYS from these callbacks and treat it like
if the callbacks were not present.

This allows of-thermal to always set the sensor related callbacks and
to make struct thermal_zone_device_ops const again.

Signed-off-by: Sascha Hauer <s.ha...@pengutronix.de>
---
 drivers/thermal/thermal_core.c | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)

diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index 6d0fdad..acf00b5 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -413,10 +413,13 @@ static void handle_thermal_trip(struct 
thermal_zone_device *tz, int trip)
  */
 int thermal_zone_get_temp(struct thermal_zone_device *tz, unsigned long *temp)
 {
-       int ret = -EINVAL;
+       int ret;
 
-       if (!tz || IS_ERR(tz) || !tz->ops->get_temp)
-               goto exit;
+       if (!tz || IS_ERR(tz))
+               return -EINVAL;
+
+       if (!tz->ops->get_temp)
+               return -ENOSYS;
 
        mutex_lock(&tz->lock);
 
@@ -426,7 +429,7 @@ int thermal_zone_get_temp(struct thermal_zone_device *tz, 
unsigned long *temp)
                *temp = tz->emul_temperature;
 
        mutex_unlock(&tz->lock);
-exit:
+
        return ret;
 }
 EXPORT_SYMBOL_GPL(thermal_zone_get_temp);
@@ -437,10 +440,11 @@ void thermal_zone_device_update(struct 
thermal_zone_device *tz)
        unsigned long temp;
        int ret;
 
-       if (!tz->ops->get_temp)
+       ret = thermal_zone_get_temp(tz, &temp);
+
+       if (ret == -ENOSYS)
                return;
 
-       ret = thermal_zone_get_temp(tz, &temp);
        if (ret) {
                dev_warn(&tz->device, "failed to read out thermal zone %d\n",
                         tz->id);
@@ -788,12 +792,16 @@ emul_temp_store(struct device *dev, struct 
device_attribute *attr,
                }
        }
 
-       if (!tz->ops->set_emul_temp) {
+       if (tz->ops->set_emul_temp)
+               ret = tz->ops->set_emul_temp(tz, temperature);
+       else
+               ret = -ENOSYS;
+
+       if (ret == -ENOSYS) {
                mutex_lock(&tz->lock);
                tz->emul_temperature = temperature;
                mutex_unlock(&tz->lock);
-       } else {
-               ret = tz->ops->set_emul_temp(tz, temperature);
+               ret = 0;
        }
 
        if (!ret)
-- 
2.1.4

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