On Sat, 23 Nov 2013 03:52:21 -0500, Steven Rostedt wrote:
> On Fri, 22 Nov 2013 23:27:57 +0900
> Namhyung Kim <namhy...@kernel.org> wrote:
>
>> [SNIP]
>> > +#define MINORBITS 20
>> > +#define MINORMASK ((1U << MINORBITS) - 1)
>> > +
>> > +#define MAJOR(dev) ((unsigned int) ((dev) >> MINORBITS))
>> > +#define MINOR(dev) ((unsigned int) ((dev) & MINORMASK))
>> > +
>> > +unsigned long long process_jbd2_dev_to_name(struct trace_seq *s,
>> > + unsigned long long *args)
>> > +{
>> > + unsigned int dev = args[0];
>> > +
>> > + trace_seq_printf(s, "%d:%d", MAJOR(dev), MINOR(dev));
>> > + return 0;
>> > +}
>> > +
>> > +unsigned long long process_jiffies_to_msecs(struct trace_seq *s,
>> > + unsigned long long *args)
>> > +{
>> > + unsigned long long jiffies = args[0];
>> > +
>> > + trace_seq_printf(s, "%lld", jiffies);
>> > + return jiffies;
>> > +}
>> > +
>> > +int PEVENT_PLUGIN_LOADER(struct pevent *pevent)
>> > +{
>> > + pevent_register_print_function(pevent,
>> > + process_jbd2_dev_to_name,
>> > + PEVENT_FUNC_ARG_STRING,
>>
>> Actually the function returns long long not string. But it seems the
>> current code doesn't care about the return type.
>
> Actually it's not representing what process_jbd2_dev_to_name() returns
> (which will always return unsigned long long), but what
> "jbd2_dev_to_name()" returns that is (was) defined in the kernel. That
> was:
>
> const char *jbd2_dev_to_name(dev_t device)
>
> When registering a function to handle, you need to express the
> prototype of that function (not the handler). The third argument is the
> ret_type of that function.
Aha, got it. Thank you for the explanation.
> But this is interesting, the ret_type doesn't seem to be used in
> event_parse.c. The return value of the callback is only done in
> eval_num_arg() where we could put a warning if the ret_type is not a
> number.
Yes. :)
Thanks,
Namhyung
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
