+/*
+ * Work out where the start offset maps into register numbers, bearing
+ * in mind that we suppress hidden registers.
+ */
+static unsigned int regmap_debugfs_get_dump_start(struct regmap *map,
+ unsigned int base,
+ loff_t from,
+ loff_t *pos)
+{
+ struct regmap_debugfs_off_cache *c = NULL;
+ loff_t p = 0;
+ unsigned int i, ret;
+
+ /*
+ * If we don't have a cache build one so we don't have to do a
+ * linear scan each time.
+ */
+ if (list_empty(&map->debugfs_off_cache)) {
+ for (i = base; i <= map->max_register; i += map->reg_stride) {
+ /* Skip unprinted registers, closing off cache entry */
+ if (!regmap_readable(map, i) ||
+ regmap_precious(map, i)) {
+ if (c) {
+ c->max = p - 1;
+ list_add_tail(&c->list,
+ &map->debugfs_off_cache);
+ c = NULL;
+ }
+
+ continue;
+ }
+
+ /* No cache entry? Start a new one */
+ if (!c) {
+ c = kzalloc(sizeof(*c), GFP_KERNEL);
+ if (!c)
+ break;
+ c->min = p;
+ c->base_reg = i;
+ }
+
+ p += map->debugfs_tot_len;
+ }
+ }
+
+ /* Find the relevant block */
+ list_for_each_entry(c, &map->debugfs_off_cache, list) {
+ if (*pos >= c->min && *pos <= c->max) {
+ *pos = c->min;
+ return c->base_reg;
+ }
+
+ ret = c->max;
+ }
+
+ return ret;
+}
+