i2c: Add message transfer tracepoints for SMBUS [ver #2]
The SMBUS tracepoints 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:
... smbus_read: i2c-0 a=051 f=0000 c=fa BYTE_DATA
... smbus_reply: i2c-0 a=051 f=0000 c=fa BYTE_DATA l=1 [39]
... smbus_result: i2c-0 a=051 f=0000 c=fa BYTE_DATA rd res=0
formatted as:
i2c-<adapter-nr>
a=<addr>
f=<flags>
c=<command>
<protocol-name>
<rd|wr>
res=<result>
l=<data-len>
[<data-block>]
The adapters to be traced can be selected by something like:
echo adapter_nr==1 >/sys/kernel/debug/tracing/events/i2c/filter
Note that this shares the same filter and enablement as i2c.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index bdedbee..7c7f4b8 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -2565,6 +2565,14 @@
int try;
s32 res;
+ /* If enabled, the following two tracepoints are conditional on
+ * read_write and protocol.
+ */
+ trace_smbus_write(adapter, addr, flags, read_write,
+ command, protocol, data);
+ trace_smbus_read(adapter, addr, flags, read_write,
+ command, protocol);
+
flags &= I2C_M_TEN | I2C_CLIENT_PEC | I2C_CLIENT_SCCB;
if (adapter->algo->smbus_xfer) {
@@ -2585,15 +2593,24 @@
i2c_unlock_adapter(adapter);
if (res != -EOPNOTSUPP || !adapter->algo->master_xfer)
- return res;
+ goto trace;
/*
* Fall back to i2c_smbus_xfer_emulated if the adapter doesn't
* implement native support for the SMBus operation.
*/
}
- return i2c_smbus_xfer_emulated(adapter, addr, flags, read_write,
- command, protocol, data);
+ res = i2c_smbus_xfer_emulated(adapter, addr, flags, read_write,
+ command, protocol, data);
+
+trace:
+ /* If enabled, the reply tracepoint is conditional on read_write. */
+ trace_smbus_reply(adapter, addr, flags, read_write,
+ command, protocol, data);
+ trace_smbus_result(adapter, addr, flags, read_write,
+ command, protocol, res);
+
+ return res;
}
EXPORT_SYMBOL(i2c_smbus_xfer);