i915: Move list_count() to list.h for broader use

Some of the existing users, and definitely will be new ones, want to
count existing nodes in the list. Provide a generic API for that by
moving code from i915 to list.h.
Reviewed-by: NLucas De Marchi <lucas.demarchi@intel.com>
Acked-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20221123144901.40493-1-andriy.shevchenko@linux.intel.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/i915/gt/intel_engine_cs.c

@@ -2004,17 +2004,6 @@ static void print_request_ring(struct drm_printer *m, struct i915_request *rq)
 	}
 }
 
-static unsigned long list_count(struct list_head *list)
-{
-	struct list_head *pos;
-	unsigned long count = 0;
-
-	list_for_each(pos, list)
-		count++;
-
-	return count;
-}
-
 static unsigned long read_ul(void *p, size_t x)
 {
 	return *(unsigned long *)(p + x);
@@ -2189,7 +2178,7 @@ void intel_engine_dump(struct intel_engine_cs *engine,
 	spin_lock_irqsave(&engine->sched_engine->lock, flags);
 	engine_dump_active_requests(engine, m);
 
-	drm_printf(m, "\tOn hold?: %lu\n",
+	drm_printf(m, "\tOn hold?: %zu\n",
 		   list_count(&engine->sched_engine->hold));
 	spin_unlock_irqrestore(&engine->sched_engine->lock, flags);
 

include/linux/list.h

@@ -655,6 +655,21 @@ static inline void list_splice_tail_init(struct list_head *list,
 	     !list_is_head(pos, (head)); \
 	     pos = n, n = pos->prev)
 
+/**
+ * list_count - count nodes in the list
+ * @head:	the head for your list.
+ */
+static inline size_t list_count(struct list_head *head)
+{
+	struct list_head *pos;
+	size_t count = 0;
+
+	list_for_each(pos, head)
+		count++;
+
+	return count;
+}
+
 /**
  * list_entry_is_head - test if the entry points to the head of the list
  * @pos:	the type * to cursor