On Wed, Dec 22, 2021 at 11:18:34PM +0900, Masami Hiramatsu wrote: > Hi Beau, > > On Thu, 16 Dec 2021 09:35:08 -0800 > Beau Belgrave <beaub@xxxxxxxxxxxxxxxxxxx> wrote: > > > Add a documentation file about user_events with example code, etc. > > explaining how it may be used. > > > > Signed-off-by: Beau Belgrave <beaub@xxxxxxxxxxxxxxxxxxx> > > --- > > Documentation/trace/index.rst | 1 + > > Documentation/trace/user_events.rst | 195 ++++++++++++++++++++++++++++ > > 2 files changed, 196 insertions(+) > > create mode 100644 Documentation/trace/user_events.rst > > > > diff --git a/Documentation/trace/index.rst b/Documentation/trace/index.rst > > index 3769b9b7aed8..3a47aa8341c6 100644 > > --- a/Documentation/trace/index.rst > > +++ b/Documentation/trace/index.rst > > @@ -30,3 +30,4 @@ Linux Tracing Technologies > > stm > > sys-t > > coresight/index > > + user_events > > diff --git a/Documentation/trace/user_events.rst b/Documentation/trace/user_events.rst > > new file mode 100644 > > index 000000000000..36104b537476 > > --- /dev/null > > +++ b/Documentation/trace/user_events.rst > > @@ -0,0 +1,195 @@ > > +========================================= > > +user_events: User-based Event Tracing > > +========================================= [..] > > +Registering > > +----------- > > +Registering within a user process is done via ioctl() out to the > > +/sys/kernel/debug/tracing/user_events_data file. The command to issue is > > +DIAG_IOCSREG. This command takes a struct user_reg as an argument. > > + > > Could you add the user_reg data structure here? > Sure thing. > > +The struct user_reg requires two values, the first is the size of the structure > > +to ensure forward and backward compatibility. The second is the command string > > +to issue for registering. > > This explanation may be a bit out of date? > user_reg has 4 fields. 2 for input, 2 for output. > Yeah, it only requires 2 inputs to work. I'll try to make this clearer. > And could you add a section for DIAG_IOCSDEL? > Sure thing. > > + > > +User based events show up under tracefs like any other event under the > > +subsystem named "user_events". This means tools that wish to attach to the > > +events need to use /sys/kernel/debug/tracing/events/user_events/[name]/enable > > +or perf record -e user_events:[name] when attaching/recording. > > + > > +**NOTE:** *The write_index returned is only valid for the FD that was used* > > + [..] > > +Example Code > > +------------ > > +See sample code in samples/user_events. > > Maybe tools/testing/selftests/user_events ? > Previously I was asked to put the sample code in samples/user_events, so it lives there. Thanks, -Beau
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