|
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>
|
