Hi,
when you want to see whats happened on the i2c bus on an raspberry pi you can enable tracing with debugfs.
Get root and mount debugfs. This is usually already mounted in raspbian
michael@debdev ~ # sudo su root@debdev ~ # mount -t debugfs none /sys/kernel/debug
Enable tracing
root@debdev ~ # echo nop > /sys/kernel/debug/tracing/current_tracer root@debdev ~ # echo 1 > /sys/kernel/debug/tracing/events/i2c/enable root@debdev ~ # echo 1 > /sys/kernel/debug/tracing/tracing_on
Generate some traffic on your i2c bus and view the trace
root@debdev ~ # cat /sys/kernel/debug/tracing/trace
To clear the current trace log
root@debdev ~ # echo > /sys/kernel/debug/tracing/trace
Michael