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

On Tue, 9 Jun 2020 11:49:19 -0400 Sean Paul sean@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