i2c: Add message transfer tracepoints for I2C

Add tracepoints into the I2C message transfer function to retrieve the message
sent or received.  The following config options must be turned on to make use
of the facility:

	CONFIG_FTRACE
	CONFIG_ENABLE_DEFAULT_TRACERS

The I2C tracepoint can be enabled thusly:

	echo 1 >/sys/kernel/debug/tracing/events/i2c/enable

and will dump messages that can be viewed in /sys/kernel/debug/tracing/trace
that look like:

	... i2c_write: i2c-5 #0 a=044 f=0000 l=2 [02-14]
	... i2c_read: i2c-5 #1 a=044 f=0001 l=4
	... i2c_reply: i2c-5 #1 a=044 f=0001 l=4 [33-00-00-00]
	... i2c_result: i2c-5 n=2 ret=2

formatted as:

	i2c-<adapter-nr>
	#<message-array-index>
	a=<addr>
	f=<flags>
	l=<datalen>
	n=<message-array-size>
	ret=<result>
	[<data>]

The operation is done between the i2c_write/i2c_read lines and the i2c_reply
and i2c_result lines so that if the hardware hangs, the trace buffer can be
consulted to determine the problematic operation.

The adapters to be traced can be selected by something like:

	echo adapter_nr==1 >/sys/kernel/debug/tracing/events/i2c/filter

These changes are based on code from Steven Rostedt.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
[wsa: adapted path for 'enable' in the commit msg]
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

1 files changed, 150 insertions, 0 deletions

diff --git a/include/trace/events/i2c.h b/include/trace/events/i2c.h
new file mode 100644
index 00000000000..4800207269a
--- /dev/null
+++ b/include/trace/events/i2c.h
@@ -0,0 +1,150 @@
+/* I2C message transfer tracepoints
+ *
+ * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM i2c
+
+#if !defined(_TRACE_I2C_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_I2C_H
+
+#include <linux/i2c.h>
+#include <linux/tracepoint.h>
+
+/*
+ * drivers/i2c/i2c-core.c
+ */
+extern void i2c_transfer_trace_reg(void);
+extern void i2c_transfer_trace_unreg(void);
+
+/*
+ * __i2c_transfer() write request
+ */
+TRACE_EVENT_FN(i2c_write,
+	       TP_PROTO(const struct i2c_adapter *adap, const struct i2c_msg *msg,
+			int num),
+	       TP_ARGS(adap, msg, num),
+	       TP_STRUCT__entry(
+		       __field(int,	adapter_nr		)
+		       __field(__u16,	msg_nr			)
+		       __field(__u16,	addr			)
+		       __field(__u16,	flags			)
+		       __field(__u16,	len			)
+		       __dynamic_array(__u8, buf, msg->len)	),
+	       TP_fast_assign(
+		       __entry->adapter_nr = adap->nr;
+		       __entry->msg_nr = num;
+		       __entry->addr = msg->addr;
+		       __entry->flags = msg->flags;
+		       __entry->len = msg->len;
+		       memcpy(__get_dynamic_array(buf), msg->buf, msg->len);
+			      ),
+	       TP_printk("i2c-%d #%u a=%03x f=%04x l=%u [%*phD]",
+			 __entry->adapter_nr,
+			 __entry->msg_nr,
+			 __entry->addr,
+			 __entry->flags,
+			 __entry->len,
+			 __entry->len, __get_dynamic_array(buf)
+			 ),
+	       i2c_transfer_trace_reg,
+	       i2c_transfer_trace_unreg);
+
+/*
+ * __i2c_transfer() read request
+ */
+TRACE_EVENT_FN(i2c_read,
+	       TP_PROTO(const struct i2c_adapter *adap, const struct i2c_msg *msg,
+			int num),
+	       TP_ARGS(adap, msg, num),
+	       TP_STRUCT__entry(
+		       __field(int,	adapter_nr		)
+		       __field(__u16,	msg_nr			)
+		       __field(__u16,	addr			)
+		       __field(__u16,	flags			)
+		       __field(__u16,	len			)
+				),
+	       TP_fast_assign(
+		       __entry->adapter_nr = adap->nr;
+		       __entry->msg_nr = num;
+		       __entry->addr = msg->addr;
+		       __entry->flags = msg->flags;
+		       __entry->len = msg->len;
+			      ),
+	       TP_printk("i2c-%d #%u a=%03x f=%04x l=%u",
+			 __entry->adapter_nr,
+			 __entry->msg_nr,
+			 __entry->addr,
+			 __entry->flags,
+			 __entry->len
+			 ),
+	       i2c_transfer_trace_reg,
+		       i2c_transfer_trace_unreg);
+
+/*
+ * __i2c_transfer() read reply
+ */
+TRACE_EVENT_FN(i2c_reply,
+	       TP_PROTO(const struct i2c_adapter *adap, const struct i2c_msg *msg,
+			int num),
+	       TP_ARGS(adap, msg, num),
+	       TP_STRUCT__entry(
+		       __field(int,	adapter_nr		)
+		       __field(__u16,	msg_nr			)
+		       __field(__u16,	addr			)
+		       __field(__u16,	flags			)
+		       __field(__u16,	len			)
+		       __dynamic_array(__u8, buf, msg->len)	),
+	       TP_fast_assign(
+		       __entry->adapter_nr = adap->nr;
+		       __entry->msg_nr = num;
+		       __entry->addr = msg->addr;
+		       __entry->flags = msg->flags;
+		       __entry->len = msg->len;
+		       memcpy(__get_dynamic_array(buf), msg->buf, msg->len);
+			      ),
+	       TP_printk("i2c-%d #%u a=%03x f=%04x l=%u [%*phD]",
+			 __entry->adapter_nr,
+			 __entry->msg_nr,
+			 __entry->addr,
+			 __entry->flags,
+			 __entry->len,
+			 __entry->len, __get_dynamic_array(buf)
+			 ),
+	       i2c_transfer_trace_reg,
+	       i2c_transfer_trace_unreg);
+
+/*
+ * __i2c_transfer() result
+ */
+TRACE_EVENT_FN(i2c_result,
+	       TP_PROTO(const struct i2c_adapter *adap, int num, int ret),
+	       TP_ARGS(adap, num, ret),
+	       TP_STRUCT__entry(
+		       __field(int,	adapter_nr		)
+		       __field(__u16,	nr_msgs			)
+		       __field(__s16,	ret			)
+				),
+	       TP_fast_assign(
+		       __entry->adapter_nr = adap->nr;
+		       __entry->nr_msgs = num;
+		       __entry->ret = ret;
+			      ),
+	       TP_printk("i2c-%d n=%u ret=%d",
+			 __entry->adapter_nr,
+			 __entry->nr_msgs,
+			 __entry->ret
+			 ),
+	       i2c_transfer_trace_reg,
+	       i2c_transfer_trace_unreg);
+
+#endif /* _TRACE_I2C_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>