[RFC PATCH] regulator: core: Add ability to create a lookup alias for supply

[RFC PATCH] regulator: core: Add ability to create a lookup alias for supply

[Charles Keepax]

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>
---

Hi Mark,

Following our discussions around the Arizona regulator
bindings here is an effort at putting a mechanism into the
regulator core to alias registering of a supply from one
device to another.

I have a couple of patches that update the Arizona driver to
use this that I will send in if you think this looks along
the lines of what you were suggesting.

Thanks,
Charles

 drivers/regulator/core.c           |   93 ++++++++++++++++++++++++++++++++++++
 include/linux/regulator/consumer.h |   17 +++++++
 2 files changed, 110 insertions(+), 0 deletions(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 6333080..e9f11f0 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 struct dentry *debugfs_root;
@@ -82,6 +83,18 @@ 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 *dev;
+	const char *supply;
+	struct device *alias;
+};
+
 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);
@@ -1208,6 +1221,28 @@ static int _regulator_get_enable_time(struct regulator_dev *rdev)
 	return rdev->desc->ops->enable_time(rdev);
 }
 
+static inline int regulator_supply_alias_match(struct device *dev,
+					       const char *supply,
+					       struct regulator_supply_alias *map)
+{
+	return map->dev == dev && strcmp(map->supply, supply) == 0;
+}
+
+static struct device *regulator_supply_alias(struct device *dev,
+					     const char *supply)
+{
+	struct regulator_supply_alias *map;
+
+	list_for_each_entry(map, &regulator_supply_alias_list, list)
+		if (regulator_supply_alias_match(dev, supply, map)) {
+			dev_dbg(dev, "Mapping supply %s to %s\n",
+				supply, dev_name(map->alias));
+			return map->alias;
+		}
+
+	return dev;
+}
+
 static struct regulator_dev *regulator_dev_lookup(struct device *dev,
 						  const char *supply,
 						  int *ret)
@@ -1217,6 +1252,8 @@ static struct regulator_dev *regulator_dev_lookup(struct device *dev,
 	struct regulator_map *map;
 	const char *devname = NULL;
 
+	dev = regulator_supply_alias(dev, supply);
+
 	/* first do a dt based lookup */
 	if (dev && dev->of_node) {
 		node = of_get_regulator(dev, supply);
@@ -1470,6 +1507,62 @@ 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: device that should be used to lookup the supply
+ *
+ * All lookups for id on dev will instead be conducted on for id on alias.
+ */
+int regulator_register_supply_alias(struct device *dev, const char *id,
+				    struct device *alias)
+{
+	struct regulator_supply_alias *map;
+
+	list_for_each_entry(map, &regulator_supply_alias_list, list)
+		if (regulator_supply_alias_match(dev, id, map))
+			return -EEXIST;
+
+	map = kzalloc(sizeof(struct regulator_supply_alias), GFP_KERNEL);
+	if (!map)
+		return -ENOMEM;
+
+	map->dev = dev;
+	map->supply = id;
+	map->alias = alias;
+
+	list_add(&map->list, &regulator_supply_alias_list);
+
+	pr_info("Adding alias for supply %s: %s -> %s\n",
+		id, dev_name(dev), dev_name(alias));
+
+	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.
+ */
+int regulator_unregister_supply_alias(struct device *dev, const char *id)
+{
+	struct regulator_supply_alias *map;
+
+	list_for_each_entry(map, &regulator_supply_alias_list, list)
+		if (regulator_supply_alias_match(dev, id, map)) {
+			list_del(&map->list);
+			kfree(map);
+			return 0;
+		}
+
+	return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(regulator_unregister_supply_alias);
+
 /* Manage enable GPIO list. Same GPIO pin can be shared among regulators */
 static int regulator_ena_gpio_request(struct regulator_dev *rdev,
 				const struct regulator_config *config)
diff --git a/include/linux/regulator/consumer.h b/include/linux/regulator/consumer.h
index 27be915..622d81e 100644
--- a/include/linux/regulator/consumer.h
+++ b/include/linux/regulator/consumer.h
@@ -146,6 +146,10 @@ struct regulator *__must_check devm_regulator_get_optional(struct device *dev,
 void regulator_put(struct regulator *regulator);
 void devm_regulator_put(struct regulator *regulator);
 
+int regulator_register_supply_alias(struct device *dev, const char *id,
+				    struct device *alias);
+int regulator_unregister_supply_alias(struct device *dev, const char *id);
+
 /* regulator output control and status */
 int __must_check regulator_enable(struct regulator *regulator);
 int regulator_disable(struct regulator *regulator);
@@ -250,6 +254,19 @@ static inline void devm_regulator_put(struct regulator *regulator)
 {
 }
 
+static inline int regulator_register_supply_alias(struct device *dev,
+						  const char *id,
+						  struct device *alias)
+{
+	return 0;
+}
+
+static inline int regulator_unregister_supply_alias(struct device *dev,
+						    const char *id)
+{
+	return 0;
+}
+
 static inline int regulator_enable(struct regulator *regulator)
 {
 	return 0;
-- 
1.7.2.5

Re: [RFC PATCH] regulator: core: Add ability to create a lookup alias for supply

[Mark Brown]

[-- Attachment #1: Type: text/plain, Size: 1305 bytes --]

On Wed, Oct 02, 2013 at 01:16:59PM +0100, Charles Keepax wrote:

> Following our discussions around the Arizona regulator
> bindings here is an effort at putting a mechanism into the
> regulator core to alias registering of a supply from one
> device to another.

This seems basically fine, though I do have a few comments below.

Bulk versions of the API would also make sense - it's likely that more
than one supply will need to be mapped - and please also add managed
versions so people don't have to write cleanup code.

> I have a couple of patches that update the Arizona driver to
> use this that I will send in if you think this looks along
> the lines of what you were suggesting.

This seems like someting that should be in the MFD core, or at least
that there should be helpers in the core.  Something like a set of
mappings in the mfd_cell so it's all data to the drivers.

> +       struct device *dev;
> +       const char *supply;
> +       struct device *alias;

Please use a more meaningful name for dev.  It might also be worth
allowing rewriting of the supply name since we'll probably find other
applications for things like modular board designs where name rewriting
is useful; since it's a function call with a parameter list it's harder
to add later than it would be with a struct.

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 836 bytes --]

Re: [RFC PATCH] regulator: core: Add ability to create a lookup alias for supply

[Charles Keepax]

On Wed, Oct 02, 2013 at 08:50:29PM +0100, Mark Brown wrote:
> Bulk versions of the API would also make sense - it's likely that more
> than one supply will need to be mapped - and please also add managed
> versions so people don't have to write cleanup code.

For the bulk API would you prefer taking a single src and alias
device and a list of supplies, or lists for all three?

I would go for a list just for the supplies, as lists of devices
would probably need to be filled in by a loop on the user end
anyway negating the point of the bulk API some what and a lot of
the use-cases will like have the same device on both sides for
all the supplies.

> > I have a couple of patches that update the Arizona driver to
> > use this that I will send in if you think this looks along
> > the lines of what you were suggesting.
> 
> This seems like someting that should be in the MFD core, or at least
> that there should be helpers in the core.  Something like a set of
> mappings in the mfd_cell so it's all data to the drivers.

Looks like a simple enough addition to the MFD core, I will
submit a patch doing it this way and see where we get to.

> Please use a more meaningful name for dev.  It might also be worth
> allowing rewriting of the supply name since we'll probably find other
> applications for things like modular board designs where name rewriting
> is useful; since it's a function call with a parameter list it's harder
> to add later than it would be with a struct.

Seems that it could be useful to change the supply name, I will
add this in as well.

Thanks,
Charles

Re: [RFC PATCH] regulator: core: Add ability to create a lookup alias for supply

[Mark Brown]

[-- Attachment #1: Type: text/plain, Size: 508 bytes --]

On Thu, Oct 03, 2013 at 05:11:14PM +0100, Charles Keepax wrote:

> For the bulk API would you prefer taking a single src and alias
> device and a list of supplies, or lists for all three?

> I would go for a list just for the supplies, as lists of devices
> would probably need to be filled in by a loop on the user end
> anyway negating the point of the bulk API some what and a lot of
> the use-cases will like have the same device on both sides for
> all the supplies.

I think just the supplies is fine.

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 836 bytes --]