The body of ddebug_attach_module_classes() is dominated by a
code-block that finds the contiguous subrange of classmaps matching on
modname, and saves it into the ddebug_table's info record.

Implement this block in a macro to accommodate different component
vectors in the "box" (as named in the for_subvec macro).  We will
reuse this macro shortly.

And hoist its invocation out of ddebug_attach_module_classes() up into
ddebug_add_module().  This moves the filtering step up closer to
dynamic_debug_init(), which already segments the builtin pr_debug
descriptors on their mod_name boundaries.

Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
v10?- reordered params to match kdoc

v12- refactor/rename: s/dd_mark_vector_subrange/dd_set_module_subrange/

1. Renamed the macro from dd_mark_vector_subrange to
   dd_set_module_subrange to better reflect its purpose of narrowing a
   vector to a module-specific subrange.

2. Simplified the arguments by removing the redundant _dst, as the _di
   pointer already provides access to the target _ddebug_info struct.

3. Refactored for Clarity: Instead of overwriting the struct's start
   pointer while the for_subvec loop is using it to iterate, I
   introduced a temporary __start variable. This avoids the "subtle"
   side effect and makes the logic easier to follow.

4. Updated Documentation: Improved the comment block to explicitly
   state that the macro scans for the first match and counts
   contiguous elements.
---
 lib/dynamic_debug.c | 37 +++++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 21ba5cb3b406..443f0fd6e8c4 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -169,8 +169,8 @@ static void vpr_info_dq(const struct ddebug_query *query, const char *msg)
 }
 
 static struct _ddebug_class_map *ddebug_find_valid_class(struct ddebug_table const *dt,
-							const char *class_string,
-							int *class_id)
+							 const char *class_string,
+							 int *class_id)
 {
 	struct _ddebug_class_map *map;
 	int i, idx;
@@ -1271,6 +1271,35 @@ static void ddebug_attach_module_classes(struct ddebug_table *dt, struct _ddebug
 	}
 }
 
+/*
+ * Narrow a _ddebug_info's vector (@_vec) to the contiguous subrange
+ * of elements where ->mod_name matches @__di->mod_name.
+ *
+ * This scans the @_di->_vec for the first element matching the module
+ * name, and counts contiguous matches to define the subrange.
+ *
+ * @_i:   caller-provided index var
+ * @_sp:  cursor into @_vec
+ * @_di:  pointer to the struct _ddebug_info to be narrowed
+ * @_vec: name of the vector member (must have .start and .len)
+ */
+#define dd_set_module_subrange(_i, _sp, _di, _vec) ({			\
+	struct _ddebug_info *__di = (_di);				\
+	typeof(__di->_vec.start) __start = NULL;			\
+	int __nc = 0;							\
+	for_subvec(_i, _sp, __di, _vec) {				\
+		if (!strcmp((_sp)->mod_name, __di->mod_name)) {		\
+			if (!__nc++)					\
+				__start = (_sp);			\
+		} else if (__nc) {					\
+			break; /* end of consecutive matches */		\
+		}							\
+	}								\
+	if (__nc)							\
+		__di->_vec.start = __start;				\
+	__di->_vec.len = __nc;						\
+})
+
 /*
  * Allocate a new ddebug_table for the given module
  * and add it to the global list.
@@ -1278,6 +1307,8 @@ static void ddebug_attach_module_classes(struct ddebug_table *dt, struct _ddebug
 static int ddebug_add_module(struct _ddebug_info *di)
 {
 	struct ddebug_table *dt;
+	struct _ddebug_class_map *cm;
+	int i;
 
 	if (!di->descs.len)
 		return 0;
@@ -1299,6 +1330,8 @@ static int ddebug_add_module(struct _ddebug_info *di)
 
 	INIT_LIST_HEAD(&dt->link);
 
+	dd_set_module_subrange(i, cm, &dt->info, maps);
+
 	if (di->maps.len)
 		ddebug_attach_module_classes(dt, di);
 
-- 
2.53.0