[lttng-dev] [PATCH lttng-modules] Add support for i2c tracepoints

[Simon Marchi]

This patch teaches lttng-modules about the i2c tracepoints in the Linux
kernel.

It contains the following tracepoints:

  * i2c_write
  * i2c_read
  * i2c_reply
  * i2c_result

I translated the fields and assignments from the kernel's
include/trace/events/i2c.h as well as I could.  I also tried building
this module against a kernel without CONFIG_I2C, and it built fine (the
required types are unconditionally defined).  So I don't think any "#if
CONFIG_I2C" or similar are required.

Signed-off-by: Simon Marchi <simon.marchi at ericsson.com>
---
 instrumentation/events/lttng-module/i2c.h | 89 +++++++++++++++++++++++++++++++
 probes/Kbuild                             |  1 +
 probes/lttng-probe-i2c.c                  | 47 ++++++++++++++++
 3 files changed, 137 insertions(+)
 create mode 100644 instrumentation/events/lttng-module/i2c.h
 create mode 100644 probes/lttng-probe-i2c.c

diff --git a/instrumentation/events/lttng-module/i2c.h b/instrumentation/events/lttng-module/i2c.h
new file mode 100644
index 0000000..68ce80d
--- /dev/null
+++ b/instrumentation/events/lttng-module/i2c.h
@@ -0,0 +1,89 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM i2c
+
+#if !defined(LTTNG_TRACE_I2C_H) || defined(TRACE_HEADER_MULTI_READ)
+#define LTTNG_TRACE_I2C_H
+
+#include <probes/lttng-tracepoint-event.h>
+
+#ifndef _TRACE_I2C_DEF_
+#define _TRACE_I2C_DEF_
+
+#endif /* _TRACE_I2C_DEF_ */
+
+/*
+ * __i2c_transfer() write request
+ */
+LTTNG_TRACEPOINT_EVENT(i2c_write,
+
+	TP_PROTO(const struct i2c_adapter *adap, const struct i2c_msg *msg, int num),
+
+	TP_ARGS(adap, msg, num),
+
+	TP_FIELDS(
+		ctf_integer(int, adapter_nr, adap->nr)
+		ctf_integer(__u16, msg_nr, num)
+		ctf_integer(__u16, addr, msg->addr)
+		ctf_integer(__u16, flags, msg->flags)
+		ctf_integer(__u16, len, msg->len)
+		ctf_sequence_hex(__u8, buf, msg->buf, __u16, msg->len)
+	)
+)
+
+/*
+ * __i2c_transfer() read request
+ */
+LTTNG_TRACEPOINT_EVENT(i2c_read,
+
+	TP_PROTO(const struct i2c_adapter *adap, const struct i2c_msg *msg, int num),
+
+	TP_ARGS(adap, msg, num),
+
+	TP_FIELDS(
+		ctf_integer(int, adapter_nr, adap->nr)
+		ctf_integer(__u16, msg_nr, num)
+		ctf_integer(__u16, addr, msg->addr)
+		ctf_integer(__u16, flags, msg->flags)
+		ctf_integer(__u16, len, msg->len)
+	)
+)
+
+/*
+ * __i2c_transfer() read reply
+ */
+LTTNG_TRACEPOINT_EVENT(i2c_reply,
+
+	TP_PROTO(const struct i2c_adapter *adap, const struct i2c_msg *msg, int num),
+
+	TP_ARGS(adap, msg, num),
+
+	TP_FIELDS(
+		ctf_integer(int, adapter_nr, adap->nr)
+		ctf_integer(__u16, msg_nr, num)
+		ctf_integer(__u16, addr, msg->addr)
+		ctf_integer(__u16, flags, msg->flags)
+		ctf_integer(__u16, len, msg->len)
+		ctf_sequence_hex(__u8, buf, msg->buf, __u16, msg->len)
+	)
+)
+
+/*
+ * __i2c_transfer() result
+ */
+LTTNG_TRACEPOINT_EVENT(i2c_result,
+
+	TP_PROTO(const struct i2c_adapter *adap, int num, int ret),
+
+	TP_ARGS(adap, num, ret),
+
+	TP_FIELDS(
+		ctf_integer(int, adapter_nr, adap->nr)
+		ctf_integer(__u16, nr_msgs, num)
+		ctf_integer(__s16, ret, ret)
+	)
+)
+
+#endif /*  LTTNG_TRACE_I2C_H */
+
+/* This part must be outside protection */
+#include <probes/define_trace.h>
diff --git a/probes/Kbuild b/probes/Kbuild
index 8ae9a6b..ca7c0b1 100644
--- a/probes/Kbuild
+++ b/probes/Kbuild
@@ -5,6 +5,7 @@ include $(TOP_LTTNG_MODULES_DIR)/Makefile.ABI.workarounds
 ccflags-y += -I$(TOP_LTTNG_MODULES_DIR)
 
 obj-$(CONFIG_LTTNG) += lttng-probe-sched.o
+obj-$(CONFIG_LTTNG) += lttng-probe-i2c.o
 obj-$(CONFIG_LTTNG) += lttng-probe-irq.o
 obj-$(CONFIG_LTTNG) += lttng-probe-timer.o
 obj-$(CONFIG_LTTNG) += lttng-probe-kmem.o
diff --git a/probes/lttng-probe-i2c.c b/probes/lttng-probe-i2c.c
new file mode 100644
index 0000000..94ebdc0
--- /dev/null
+++ b/probes/lttng-probe-i2c.c
@@ -0,0 +1,47 @@
+/*
+ * probes/lttng-probe-i2c.c
+ *
+ * LTTng i2c probes.
+ *
+ * Copyright (C) 2012 Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; only
+ * version 2.1 of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <linux/module.h>
+#include <lttng-tracer.h>
+
+/*
+ * Create the tracepoint static inlines from the kernel to validate that our
+ * trace event macros match the kernel we run on.
+ */
+#include <trace/events/i2c.h>
+
+/*
+ * Create LTTng tracepoint probes.
+ */
+#define LTTNG_PACKAGE_BUILD
+#define CREATE_TRACE_POINTS
+#define TRACE_INCLUDE_PATH instrumentation/events/lttng-module
+
+#include <instrumentation/events/lttng-module/i2c.h>
+
+MODULE_LICENSE("GPL and additional rights");
+MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers at efficios.com>");
+MODULE_DESCRIPTION("LTTng i2c probes");
+MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
+	__stringify(LTTNG_MODULES_MINOR_VERSION) "."
+	__stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
+	LTTNG_MODULES_EXTRAVERSION);
-- 
2.9.3