On Thu, Jan 09, 2014 at 09:49:54PM +0000, David Howells wrote: > 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/i2c_transfer/enable > > and will dump messages that can be viewed in /sys/kernel/debug/tracing/trace > that look like: > > ... i2c_write: i2c-5 #0 f=00 a=44 l=2 [0214] > ... i2c_read: i2c-5 #1 f=01 a=44 l=4 > ... i2c_reply: i2c-5 #1 f=01 a=44 l=4 [33000000] > ... i2c_result: i2c-5 n=2 ret=2 > > formatted as: > > i2c-<adapter-nr> > #<message-array-index> > f=<flags> > a=<addr> > 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@xxxxxxxxxxx> > Signed-off-by: David Howells <dhowells@xxxxxxxxxx> > Reviewed-by: Steven Rostedt <rostedt@xxxxxxxxxxx> Thanks for doing this, much appreciated. One of the first things I'll review (and play with) next. But hey, has nobody else checked this out by now? Tested-by or acks very welcome. Thanks, Wolfram
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