hwmon: Introduce 64-bit energy attribute support

Many chips require 64-bit variables to display the accumulated energy,
even more so since the energy units are micro-Joule. Add new sensor type
"energy64" to support reporting the chip energy as 64-bit values.

Changing the entire hardware monitoring API is not feasible, and it is only
really necessary to support reading 64-bit values for the "energyX_input"
attribute. For this reason, keep the API as-is and use type casts on both
ends to pass 64-bit pointers when reading the accumulated energy. On the
write side (which is only useful for the energyX_enable attribute), keep
passing the written value as long.

Reviewed-by: Chris Packham <[e-mail]>
Tested-by: Chris Packham <[e-mail]> # INA780
Signed-off-by: Guenter Roeck <[e-mail]>

Documentation/hwmon/hwmon-kernel-api.rst

···
      hwmon_curr		Current sensor
      hwmon_power		Power sensor
      hwmon_energy	Energy sensor
+     hwmon_energy64	Energy sensor, reported as 64-bit signed value
      hwmon_humidity	Humidity sensor
      hwmon_fan		Fan speed sensor
      hwmon_pwm		PWM control
···
 		The sensor channel number.
 	val:
 		Pointer to attribute value.
+		For hwmon_energy64, `'val`' is passed as `long *` but needs
+		a typecast to `s64 *`.
 
 Return value:
 	0 on success, a negative error number otherwise.

drivers/hwmon/hwmon.c

···
 			       struct device_attribute *devattr, char *buf)
 {
 	struct hwmon_device_attribute *hattr = to_hwmon_attr(devattr);
+	s64 val64;
 	long val;
 	int ret;
 
 	ret = hattr->ops->read(dev, hattr->type, hattr->attr, hattr->index,
-			       &val);
+			       (hattr->type == hwmon_energy64) ? (long *)&val64 : &val);
 	if (ret < 0)
 		return ret;
 
-	trace_hwmon_attr_show(hattr->index + hwmon_attr_base(hattr->type),
-			      hattr->name, val);
+	if (hattr->type != hwmon_energy64)
+		val64 = val;
 
-	return sprintf(buf, "%ld\n", val);
+	trace_hwmon_attr_show(hattr->index + hwmon_attr_base(hattr->type),
+			      hattr->name, val64);
+
+	return sprintf(buf, "%lld\n", val64);
 }
 
 static ssize_t hwmon_attr_show_string(struct device *dev,
···
 		return ret;
 
 	trace_hwmon_attr_store(hattr->index + hwmon_attr_base(hattr->type),
-			       hattr->name, val);
+			       hattr->name, (s64)val);
 
 	return count;
 }
···
 	[hwmon_curr] = hwmon_curr_attr_templates,
 	[hwmon_power] = hwmon_power_attr_templates,
 	[hwmon_energy] = hwmon_energy_attr_templates,
+	[hwmon_energy64] = hwmon_energy_attr_templates,
 	[hwmon_humidity] = hwmon_humidity_attr_templates,
 	[hwmon_fan] = hwmon_fan_attr_templates,
 	[hwmon_pwm] = hwmon_pwm_attr_templates,
···
 	[hwmon_curr] = ARRAY_SIZE(hwmon_curr_attr_templates),
 	[hwmon_power] = ARRAY_SIZE(hwmon_power_attr_templates),
 	[hwmon_energy] = ARRAY_SIZE(hwmon_energy_attr_templates),
+	[hwmon_energy64] = ARRAY_SIZE(hwmon_energy_attr_templates),
 	[hwmon_humidity] = ARRAY_SIZE(hwmon_humidity_attr_templates),
 	[hwmon_fan] = ARRAY_SIZE(hwmon_fan_attr_templates),
 	[hwmon_pwm] = ARRAY_SIZE(hwmon_pwm_attr_templates),

include/linux/hwmon.h

···
 	hwmon_curr,
 	hwmon_power,
 	hwmon_energy,
+	hwmon_energy64,
 	hwmon_humidity,
 	hwmon_fan,
 	hwmon_pwm,

include/trace/events/hwmon.h

···
 
 DECLARE_EVENT_CLASS(hwmon_attr_class,
 
-	TP_PROTO(int index, const char *attr_name, long val),
+	TP_PROTO(int index, const char *attr_name, long long val),
 
 	TP_ARGS(index, attr_name, val),
 
 	TP_STRUCT__entry(
 		__field(int, index)
 		__string(attr_name, attr_name)
-		__field(long, val)
+		__field(long long, val)
 	),
 
 	TP_fast_assign(
···
 		__entry->val = val;
 	),
 
-	TP_printk("index=%d, attr_name=%s, val=%ld",
+	TP_printk("index=%d, attr_name=%s, val=%lld",
 		  __entry->index,  __get_str(attr_name), __entry->val)
 );
 
 DEFINE_EVENT(hwmon_attr_class, hwmon_attr_show,
 
-	TP_PROTO(int index, const char *attr_name, long val),
+	TP_PROTO(int index, const char *attr_name, long long val),
 
 	TP_ARGS(index, attr_name, val)
 );
 
 DEFINE_EVENT(hwmon_attr_class, hwmon_attr_store,
 
-	TP_PROTO(int index, const char *attr_name, long val),
+	TP_PROTO(int index, const char *attr_name, long long val),
 
 	TP_ARGS(index, attr_name, val)
 );