[PATCH v6 13/13] drm/print: Add tracefs support to the drm logging helpers

[Steven Rostedt]

On Tue,  9 Jun 2020 11:49:19 -0400
Sean Paul <sean at poorly.run> wrote:

> +/**
> + * drm_trace_printf - adds an entry to the drm tracefs instance
> + * @format: printf format of the message to add to the trace
> + *
> + * This function adds a new entry in the drm tracefs instance
> + */
> +void drm_trace_printf(const char *format, ...)
> +{
> +	struct va_format vaf;
> +	va_list args;
> +
> +	va_start(args, format);
> +	vaf.fmt = format;
> +	vaf.va = &args;
> +	trace_array_printk(trace_arr, _THIS_IP_, "%pV", &vaf);
> +	va_end(args);
> +}

The only issue I have with this patch is the above. I really dislike
the use of trace_array_print(), as that is made to be for debugging and
not something that should be in a production kernel.

Ideally, every instance should just pass the data it wants to record,
and you add it to a trace event. There's already a drm trace subsystem,
how would this be different. Perhaps create a drm_log subsystem, and
you only need to have your instance enable it?

I guess I'm still confused to why this is needed over just having trace
events? What's special about this case?

-- Steve