Re: [PATCH v5 01/12] libtracefs: New APIs for dynamic events

[Steven Rostedt <rostedt@goodmis.org>]

On Fri,  5 Nov 2021 14:16:13 +0200
"Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com> wrote:

> +static void init_devent_desc(void)
> +{
> +	int i;
> +
> +	BUILD_BUG_ON(ARRAY_SIZE(dynevents) != max_dyn_index);
> +
> +	/* Use  ftrace dynamic_events, if available */
> +	if (tracefs_file_exists(NULL, DYNEVENTS_EVENTS)) {
> +		for (i = 0; i < max_dyn_index; i++)
> +			dynevents[i].file = DYNEVENTS_EVENTS;
> +		return;
> +	}
> +
> +	if (tracefs_file_exists(NULL, KPROBE_EVENTS)) {
> +		dynevents[ffs(TRACEFS_DYNEVENT_KPROBE) - 1].file = KPROBE_EVENTS;
> +		dynevents[ffs(TRACEFS_DYNEVENT_KRETPROBE) - 1].file = KPROBE_EVENTS;
> +	}
> +	if (tracefs_file_exists(NULL, UPROBE_EVENTS)) {
> +		dynevents[ffs(TRACEFS_DYNEVENT_UPROBE) - 1].file = UPROBE_EVENTS;
> +		dynevents[ffs(TRACEFS_DYNEVENT_URETPROBE) - 1].file = UPROBE_EVENTS;
> +	}
> +	if (tracefs_file_exists(NULL, SYNTH_EVENTS)) {
> +		dynevents[ffs(TRACEFS_DYNEVENT_SYNTH) - 1].file = SYNTH_EVENTS;
> +		dynevents[ffs(TRACEFS_DYNEVENT_SYNTH) - 1].prefix = "";
> +	}
> +}
> +

I would have kept your bit_index() function to simplify the above. I just
meant to use ffs in that function.

static inline bit_index(unsigned int bits)
{
	return ffs(bits) - 1;
}

-- Steve