i2c: add tracepoints for I2C slave events

I2C slave events tracepoints can be enabled by:

	echo 1 > /sys/kernel/tracing/events/i2c_slave/enable

and logs in /sys/kernel/tracing/trace will look like:

	... i2c_slave: i2c-0 a=010 ret=0 WR_REQ []
	... i2c_slave: i2c-0 a=010 ret=0 WR_RCV [02]
	... i2c_slave: i2c-0 a=010 ret=0 WR_RCV [0c]
	... i2c_slave: i2c-0 a=010 ret=0   STOP []
	... i2c_slave: i2c-0 a=010 ret=0 RD_REQ [04]
	... i2c_slave: i2c-0 a=010 ret=0 RD_PRO [b4]
	... i2c_slave: i2c-0 a=010 ret=0  STOP []

formatted as:

	i2c-<adapter_nr>
	a=<addr>
	ret=<ret>	<- callback return value
	<event>
	[<data>]

trace printings can be selected by adding a filter like:

	echo adapter_nr==1 >/sys/kernel/tracing/events/i2c_slave/filter
Signed-off-by: Jae Hyun Yoo <quic_jaehyoo@quicinc.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

drivers/i2c/i2c-core-slave.c

@@ -14,6 +14,9 @@
 
 #include "i2c-core.h"
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/i2c_slave.h>
+
 int i2c_slave_register(struct i2c_client *client, i2c_slave_cb_t slave_cb)
 {
 	int ret;
@@ -79,6 +82,18 @@ int i2c_slave_unregister(struct i2c_client *client)
 }
 EXPORT_SYMBOL_GPL(i2c_slave_unregister);
 
+int i2c_slave_event(struct i2c_client *client,
+		    enum i2c_slave_event event, u8 *val)
+{
+	int ret = client->slave_cb(client, event, val);
+
+	if (trace_i2c_slave_enabled())
+		trace_i2c_slave(client, event, val, ret);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(i2c_slave_event);
+
 /**
  * i2c_detect_slave_mode - detect operation mode
  * @dev: The device owning the bus

include/linux/i2c.h

@@ -392,12 +392,8 @@ enum i2c_slave_event {
 int i2c_slave_register(struct i2c_client *client, i2c_slave_cb_t slave_cb);
 int i2c_slave_unregister(struct i2c_client *client);
 bool i2c_detect_slave_mode(struct device *dev);
-
-static inline int i2c_slave_event(struct i2c_client *client,
-				  enum i2c_slave_event event, u8 *val)
-{
-	return client->slave_cb(client, event, val);
-}
+int i2c_slave_event(struct i2c_client *client,
+		    enum i2c_slave_event event, u8 *val);
 #else
 static inline bool i2c_detect_slave_mode(struct device *dev) { return false; }
 #endif

include/trace/events/i2c_slave.h

+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * I2C slave tracepoints
+ *
+ * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM i2c_slave
+
+#if !defined(_TRACE_I2C_SLAVE_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_I2C_SLAVE_H
+
+#include <linux/i2c.h>
+#include <linux/tracepoint.h>
+
+TRACE_DEFINE_ENUM(I2C_SLAVE_READ_REQUESTED);
+TRACE_DEFINE_ENUM(I2C_SLAVE_WRITE_REQUESTED);
+TRACE_DEFINE_ENUM(I2C_SLAVE_READ_PROCESSED);
+TRACE_DEFINE_ENUM(I2C_SLAVE_WRITE_RECEIVED);
+TRACE_DEFINE_ENUM(I2C_SLAVE_STOP);
+
+#define show_event_type(type)						\
+	__print_symbolic(type,						\
+		{ I2C_SLAVE_READ_REQUESTED,	"RD_REQ" },		\
+		{ I2C_SLAVE_WRITE_REQUESTED,	"WR_REQ" },		\
+		{ I2C_SLAVE_READ_PROCESSED,	"RD_PRO" },		\
+		{ I2C_SLAVE_WRITE_RECEIVED,	"WR_RCV" },		\
+		{ I2C_SLAVE_STOP,		"  STOP" })
+
+TRACE_EVENT(i2c_slave,
+	TP_PROTO(const struct i2c_client *client, enum i2c_slave_event event,
+		 __u8 *val, int cb_ret),
+	TP_ARGS(client, event, val, cb_ret),
+	TP_STRUCT__entry(
+		__field(int,				adapter_nr	)
+		__field(int,				ret		)
+		__field(__u16,				addr		)
+		__field(__u16,				len		)
+		__field(enum i2c_slave_event,		event		)
+		__array(__u8,				buf,	1)	),
+
+	TP_fast_assign(
+		__entry->adapter_nr = client->adapter->nr;
+		__entry->addr = client->addr;
+		__entry->event = event;
+		__entry->ret = cb_ret;
+		switch (event) {
+		case I2C_SLAVE_READ_REQUESTED:
+		case I2C_SLAVE_READ_PROCESSED:
+		case I2C_SLAVE_WRITE_RECEIVED:
+			__entry->len = 1;
+			memcpy(__entry->buf, val, __entry->len);
+			break;
+		default:
+			__entry->len = 0;
+			break;
+		}
+		),
+	TP_printk("i2c-%d a=%03x ret=%d %s [%*phD]",
+		__entry->adapter_nr, __entry->addr, __entry->ret,
+		show_event_type(__entry->event), __entry->len, __entry->buf
+		));
+
+#endif /* _TRACE_I2C_SLAVE_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>