[PATCH v2] hwmon: (core) Add trace events to _attr_show/store functions

[Nicolin Chen]

Trace events are useful for people who collect data from the
Ftrace outputs. There're people who analyse the relationship
of cpufreq, thermal and hwmon (power/voltage/current) using
the convenient and timestamped Ftrace outputs, while unlike
cpufreq and thermal subsystems the hwmon does not have trace
events supported yet.

So this patch adds initial trace events for the hwmon core.
To call hwmon_attr_base() for aligned attr index numbers, it
also moves the function upward.

Ftrace outputs:
 ...: hwmon_attr_show_string: index=2, attr_name=in2_label, val=VDD_5V
 ...: hwmon_attr_show: index=2, attr_name=in2_input, val=5112
 ...: hwmon_attr_show: index=2, attr_name=curr2_input, val=440

Note that the _attr_show and _attr_store functions are tied
to the _with_info API. So a hwmon driver requiring the trace
events feature should use _with_info API to register a hwmon
device.

Signed-off-by: Nicolin Chen <nicoleotsuka@xxxxxxxxx>
---
Changelog
v1->v2:
 * Added a descriptive reason for this change in the commit message

 MAINTAINERS                  |  1 +
 drivers/hwmon/hwmon.c        | 27 ++++++++++----
 include/trace/events/hwmon.h | 71 ++++++++++++++++++++++++++++++++++++
 3 files changed, 92 insertions(+), 7 deletions(-)
 create mode 100644 include/trace/events/hwmon.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 1640b9faa75e..589b32405bf4 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6461,6 +6461,7 @@ F:	Documentation/devicetree/bindings/hwmon/
 F:	Documentation/hwmon/
 F:	drivers/hwmon/
 F:	include/linux/hwmon*.h
+F:	include/trace/events/hwmon*.h
 
 HARDWARE RANDOM NUMBER GENERATOR CORE
 M:	Matt Mackall <mpm@xxxxxxxxxxx>
diff --git a/drivers/hwmon/hwmon.c b/drivers/hwmon/hwmon.c
index ac1cdf88840f..975c95169884 100644
--- a/drivers/hwmon/hwmon.c
+++ b/drivers/hwmon/hwmon.c
@@ -24,6 +24,9 @@
 #include <linux/string.h>
 #include <linux/thermal.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/hwmon.h>
+
 #define HWMON_ID_PREFIX "hwmon"
 #define HWMON_ID_FORMAT HWMON_ID_PREFIX "%d"
 
@@ -171,6 +174,13 @@ static int hwmon_thermal_add_sensor(struct device *dev,
 }
 #endif /* IS_REACHABLE(CONFIG_THERMAL) && ... */
 
+static int hwmon_attr_base(enum hwmon_sensor_types type)
+{
+	if (type == hwmon_in)
+		return 0;
+	return 1;
+}
+
 /* sysfs attribute management */
 
 static ssize_t hwmon_attr_show(struct device *dev,
@@ -185,6 +195,9 @@ static ssize_t hwmon_attr_show(struct device *dev,
 	if (ret < 0)
 		return ret;
 
+	trace_hwmon_attr_show(hattr->index + hwmon_attr_base(hattr->type),
+			      hattr->name, val);
+
 	return sprintf(buf, "%ld\n", val);
 }
 
@@ -193,6 +206,7 @@ static ssize_t hwmon_attr_show_string(struct device *dev,
 				      char *buf)
 {
 	struct hwmon_device_attribute *hattr = to_hwmon_attr(devattr);
+	enum hwmon_sensor_types type = hattr->type;
 	const char *s;
 	int ret;
 
@@ -201,6 +215,9 @@ static ssize_t hwmon_attr_show_string(struct device *dev,
 	if (ret < 0)
 		return ret;
 
+	trace_hwmon_attr_show_string(hattr->index + hwmon_attr_base(type),
+				     hattr->name, s);
+
 	return sprintf(buf, "%s\n", s);
 }
 
@@ -221,16 +238,12 @@ static ssize_t hwmon_attr_store(struct device *dev,
 	if (ret < 0)
 		return ret;
 
+	trace_hwmon_attr_store(hattr->index + hwmon_attr_base(hattr->type),
+			       hattr->name, val);
+
 	return count;
 }
 
-static int hwmon_attr_base(enum hwmon_sensor_types type)
-{
-	if (type == hwmon_in)
-		return 0;
-	return 1;
-}
-
 static bool is_string_attr(enum hwmon_sensor_types type, u32 attr)
 {
 	return (type == hwmon_temp && attr == hwmon_temp_label) ||
diff --git a/include/trace/events/hwmon.h b/include/trace/events/hwmon.h
new file mode 100644
index 000000000000..d7a1d0ffb679
--- /dev/null
+++ b/include/trace/events/hwmon.h
@@ -0,0 +1,71 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM hwmon
+
+#if !defined(_TRACE_HWMON_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_HWMON_H
+
+#include <linux/tracepoint.h>
+
+DECLARE_EVENT_CLASS(hwmon_attr_class,
+
+	TP_PROTO(int index, const char *attr_name, long val),
+
+	TP_ARGS(index, attr_name, val),
+
+	TP_STRUCT__entry(
+		__field(int, index)
+		__string(attr_name, attr_name)
+		__field(long, val)
+	),
+
+	TP_fast_assign(
+		__entry->index = index;
+		__assign_str(attr_name, attr_name);
+		__entry->val = val;
+	),
+
+	TP_printk("index=%d, attr_name=%s, val=%ld",
+		  __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_ARGS(index, attr_name, val)
+);
+
+DEFINE_EVENT(hwmon_attr_class, hwmon_attr_store,
+
+	TP_PROTO(int index, const char *attr_name, long val),
+
+	TP_ARGS(index, attr_name, val)
+);
+
+TRACE_EVENT(hwmon_attr_show_string,
+
+	TP_PROTO(int index, const char *attr_name, const char *s),
+
+	TP_ARGS(index, attr_name, s),
+
+	TP_STRUCT__entry(
+		__field(int, index)
+		__string(attr_name, attr_name)
+		__string(label, s)
+	),
+
+	TP_fast_assign(
+		__entry->index = index;
+		__assign_str(attr_name, attr_name);
+		__assign_str(label, s);
+	),
+
+	TP_printk("index=%d, attr_name=%s, val=%s",
+		  __entry->index, __get_str(attr_name), __get_str(label))
+);
+
+#endif /* _TRACE_HWMON_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
-- 
2.17.1