drm/print: rename drm_debug to __drm_debug to discourage use

drm_debug_enabled() is the way to check. __drm_debug is now reserved for
drm print code only. No functional changes.

v2: Rebase on move unlikely() to drm_debug_enabled()
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Eric Engestrom <eric@engestrom.ch>
Acked-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Sean Paul <sean@poorly.run>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/840ff7292d1a39512bac2fcb1f45de9d50694bf1.1572258936.git.jani.nikula@intel.com

drivers/gpu/drm/drm_print.c

@@ -37,11 +37,11 @@
 #include <drm/drm_print.h>
 
 /*
- * drm_debug: Enable debug output.
+ * __drm_debug: Enable debug output.
  * Bitmask of DRM_UT_x. See include/drm/drm_print.h for details.
  */
-unsigned int drm_debug;
-EXPORT_SYMBOL(drm_debug);
+unsigned int __drm_debug;
+EXPORT_SYMBOL(__drm_debug);
 
 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"
@@ -52,7 +52,7 @@ MODULE_PARM_DESC(debug, "Enable debug output, where each bit enables a debug cat
 "\t\tBit 5 (0x20)  will enable VBL messages (vblank code)\n"
 "\t\tBit 7 (0x80)  will enable LEASE messages (leasing code)\n"
 "\t\tBit 8 (0x100) will enable DP messages (displayport code)");
-module_param_named(debug, drm_debug, int, 0600);
+module_param_named(debug, __drm_debug, int, 0600);
 
 void __drm_puts_coredump(struct drm_printer *p, const char *str)
 {

include/drm/drm_print.h

@@ -34,7 +34,8 @@
 
 #include <drm/drm.h>
 
-extern unsigned int drm_debug;
+/* Do *not* use outside of drm_print.[ch]! */
+extern unsigned int __drm_debug;
 
 /**
  * DOC: print
@@ -295,7 +296,7 @@ static inline struct drm_printer drm_err_printer(const char *prefix)
 
 static inline bool drm_debug_enabled(unsigned int category)
 {
-	return unlikely(drm_debug & category);
+	return unlikely(__drm_debug & category);
 }
 
 __printf(3, 4)