drm-formats: add weston_drm_format_array_count_pairs()

It simply returns the number of format/modifier pairs in the array. This
will be useful for the next commits, in which we add support for dma-buf
feedback.

Signed-off-by: Leandro Ribeiro <leandro.ribeiro@collabora.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>

libweston/drm-formats.c

@@ -184,6 +184,24 @@ weston_drm_format_array_find_format(const struct weston_drm_format_array *format
 	return NULL;
 }
 
+/**
+ * Counts the number of format/modifier pairs in a weston_drm_format_array
+ *
+ * @param formats The weston_drm_format_array
+ * @return The number of format/modifier pairs in the array
+ */
+WL_EXPORT unsigned int
+weston_drm_format_array_count_pairs(const struct weston_drm_format_array *formats)
+{
+	struct weston_drm_format *fmt;
+	unsigned int num_pairs = 0;
+
+	wl_array_for_each(fmt, &formats->arr)
+		num_pairs += fmt->modifiers.size / sizeof(uint64_t);
+
+	return num_pairs;
+}
+
 /**
  * Compare the content of two weston_drm_format_array
  *

libweston/libweston-internal.h

@@ -358,6 +358,9 @@ struct weston_drm_format *
 weston_drm_format_array_find_format(const struct weston_drm_format_array *formats,
 				    uint32_t format);
 
+unsigned int
+weston_drm_format_array_count_pairs(const struct weston_drm_format_array *formats);
+
 bool
 weston_drm_format_array_equal(const struct weston_drm_format_array *formats_A,
 			      const struct weston_drm_format_array *formats_B);