regulator: core: Add ability to create a lookup alias for supply

These patches add the ability to create an alternative device on which
a lookup for a certain supply should be conducted.

A common use-case for this would be devices that are logically
represented as a collection of drivers within Linux but are are
presented as a single device from device tree. It this case it is
necessary for each sub device to locate their supply data on the main
device.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

3 files changed, 412 insertions, 0 deletions

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 906deb7354ed..16427de56ce8 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -53,6 +53,7 @@ static DEFINE_MUTEX(regulator_list_mutex);
 static LIST_HEAD(regulator_list);
 static LIST_HEAD(regulator_map_list);
 static LIST_HEAD(regulator_ena_gpio_list);
+static LIST_HEAD(regulator_supply_alias_list);
 static bool has_full_constraints;
 static bool board_wants_dummy_regulator;
 
@@ -83,6 +84,19 @@ struct regulator_enable_gpio {
         unsigned int ena_gpio_invert:1;
 };
 
+/*
+ * struct regulator_supply_alias
+ *
+ * Used to map lookups for a supply onto an alternative device.
+ */
+struct regulator_supply_alias {
+        struct list_head list;
+        struct device *src_dev;
+        const char *src_supply;
+        struct device *alias_dev;
+        const char *alias_supply;
+};
+
 static int _regulator_is_enabled(struct regulator_dev *rdev);
 static int _regulator_disable(struct regulator_dev *rdev);
 static int _regulator_get_voltage(struct regulator_dev *rdev);
@@ -1173,6 +1187,32 @@ static int _regulator_get_enable_time(struct regulator_dev *rdev)
         return rdev->desc->ops->enable_time(rdev);
 }
 
+static struct regulator_supply_alias *regulator_find_supply_alias(
+                struct device *dev, const char *supply)
+{
+        struct regulator_supply_alias *map;
+
+        list_for_each_entry(map, &regulator_supply_alias_list, list)
+                if (map->src_dev == dev && strcmp(map->src_supply, supply) == 0)
+                        return map;
+
+        return NULL;
+}
+
+static void regulator_supply_alias(struct device **dev, const char **supply)
+{
+        struct regulator_supply_alias *map;
+
+        map = regulator_find_supply_alias(*dev, *supply);
+        if (map) {
+                dev_dbg(*dev, "Mapping supply %s to %s,%s\n",
+                                *supply, map->alias_supply,
+                                dev_name(map->alias_dev));
+                *dev = map->alias_dev;
+                *supply = map->alias_supply;
+        }
+}
+
 static struct regulator_dev *regulator_dev_lookup(struct device *dev,
                                                   const char *supply,
                                                   int *ret)
@@ -1182,6 +1222,8 @@ static struct regulator_dev *regulator_dev_lookup(struct device *dev,
         struct regulator_map *map;
         const char *devname = NULL;
 
+        regulator_supply_alias(&dev, &supply);
+
         /* first do a dt based lookup */
         if (dev && dev->of_node) {
                 node = of_get_regulator(dev, supply);
@@ -1432,6 +1474,134 @@ void regulator_put(struct regulator *regulator)
 }
 EXPORT_SYMBOL_GPL(regulator_put);
 
+/**
+ * regulator_register_supply_alias - Provide device alias for supply lookup
+ *
+ * @dev: device that will be given as the regulator "consumer"
+ * @id: Supply name or regulator ID
+ * @alias_dev: device that should be used to lookup the supply
+ * @alias_id: Supply name or regulator ID that should be used to lookup the
+ * supply
+ *
+ * All lookups for id on dev will instead be conducted for alias_id on
+ * alias_dev.
+ */
+int regulator_register_supply_alias(struct device *dev, const char *id,
+                                    struct device *alias_dev,
+                                    const char *alias_id)
+{
+        struct regulator_supply_alias *map;
+
+        map = regulator_find_supply_alias(dev, id);
+        if (map)
+                return -EEXIST;
+
+        map = kzalloc(sizeof(struct regulator_supply_alias), GFP_KERNEL);
+        if (!map)
+                return -ENOMEM;
+
+        map->src_dev = dev;
+        map->src_supply = id;
+        map->alias_dev = alias_dev;
+        map->alias_supply = alias_id;
+
+        list_add(&map->list, &regulator_supply_alias_list);
+
+        pr_info("Adding alias for supply %s,%s -> %s,%s\n",
+                id, dev_name(dev), alias_id, dev_name(alias_dev));
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(regulator_register_supply_alias);
+
+/**
+ * regulator_unregister_supply_alias - Remove device alias
+ *
+ * @dev: device that will be given as the regulator "consumer"
+ * @id: Supply name or regulator ID
+ *
+ * Remove a lookup alias if one exists for id on dev.
+ */
+void regulator_unregister_supply_alias(struct device *dev, const char *id)
+{
+        struct regulator_supply_alias *map;
+
+        map = regulator_find_supply_alias(dev, id);
+        if (map) {
+                list_del(&map->list);
+                kfree(map);
+        }
+}
+EXPORT_SYMBOL_GPL(regulator_unregister_supply_alias);
+
+/**
+ * regulator_bulk_register_supply_alias - register multiple aliases
+ *
+ * @dev: device that will be given as the regulator "consumer"
+ * @id: List of supply names or regulator IDs
+ * @alias_dev: device that should be used to lookup the supply
+ * @alias_id: List of supply names or regulator IDs that should be used to
+ * lookup the supply
+ * @num_id: Number of aliases to register
+ *
+ * @return 0 on success, an errno on failure.
+ *
+ * This helper function allows drivers to register several supply
+ * aliases in one operation.  If any of the aliases cannot be
+ * registered any aliases that were registered will be removed
+ * before returning to the caller.
+ */
+int regulator_bulk_register_supply_alias(struct device *dev, const char **id,
+                                         struct device *alias_dev,
+                                         const char **alias_id,
+                                         int num_id)
+{
+        int i;
+        int ret;
+
+        for (i = 0; i < num_id; ++i) {
+                ret = regulator_register_supply_alias(dev, id[i], alias_dev,
+                                                      alias_id[i]);
+                if (ret < 0)
+                        goto err;
+        }
+
+        return 0;
+
+err:
+        dev_err(dev,
+                "Failed to create supply alias %s,%s -> %s,%s\n",
+                id[i], dev_name(dev), alias_id[i], dev_name(alias_dev));
+
+        while (--i >= 0)
+                regulator_unregister_supply_alias(dev, id[i]);
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(regulator_bulk_register_supply_alias);
+
+/**
+ * regulator_bu