[PATCH v4 36/41] dyndbg/drm: POC add tracebits sysfs-knob

[Jim Cromie <jim.cromie@xxxxxxxxx>]

clone DRM.debug interface to DRM.tracebits: ie declare __drm_trace,
map its bits to drm-debug-categories, except this interface enables
messages to tracefs, not to syslog.

1- we reuse the drm_debug_classes class-map added previously.
   this reflects the single source of both syslog/trace events
   and is why structs classmap and bitmap-param are separate.

2- add a 2nd struct ddebug_classes_bitmap_param
   refs 1, reusing it.
   flags = "T", to enable trace-events on this callsite.

3- module_param_cb([2]) - does the sysfs part

Signed-off-by: Jim Cromie <jim.cromie@xxxxxxxxx>
---
 drivers/gpu/drm/drm_print.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/drm_print.c b/drivers/gpu/drm/drm_print.c
index 9fb0b8e40dca..47a41d96beea 100644
--- a/drivers/gpu/drm/drm_print.c
+++ b/drivers/gpu/drm/drm_print.c
@@ -45,6 +45,9 @@
 unsigned long __drm_debug;
 EXPORT_SYMBOL(__drm_debug);
 
+unsigned long __drm_trace;
+EXPORT_SYMBOL(__drm_trace);
+
 MODULE_PARM_DESC(debug, "Enable debug output, where each bit enables a debug category.\n"
 "\t\tBit 0 (0x01)  will enable CORE messages (drm core code)\n"
 "\t\tBit 1 (0x02)  will enable DRIVER messages (drm controller code)\n"
@@ -77,6 +80,13 @@ static struct ddebug_classes_bitmap_param drm_debug_bitmap = {
 	.map = &drm_debug_classes,
 };
 module_param_cb(debug, &param_ops_dyndbg_classes, &drm_debug_bitmap, 0600);
+
+static struct ddebug_classes_bitmap_param drm_trace_bitmap = {
+	.bits = &__drm_trace,
+	.flags = "T",
+	.map = &drm_debug_classes,
+};
+module_param_cb(tracecats, &param_ops_dyndbg_classes, &drm_trace_bitmap, 0600);
 #endif
 
 void __drm_puts_coredump(struct drm_printer *p, const char *str)
-- 
2.36.1