nvmem: add support for cell lookups from machine code

Add a way for machine code users to associate devices with nvmem cells.

This restores the support for non-DT systems but following a different
approach. Cells must now be associated with devices using provided
routines and data structures before they can be retrieved using
nvmem_cell_get().

It's still possible to define cells statically in nvmem_config but
cells created this way still need to be associated with consumers using
lookup entries.

Note that nvmem_find() must be moved higher in the source file as we
want to call it from __nvmem_device_get() for devices that don't have
a device node.

The signature of __nvmem_device_get() is also changed as it's no longer
used to retrieve cells.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/nvmem/core.c

@@ -62,6 +62,9 @@ static DEFINE_IDA(nvmem_ida);
 static DEFINE_MUTEX(nvmem_cell_mutex);
 static LIST_HEAD(nvmem_cell_tables);
 
+static DEFINE_MUTEX(nvmem_lookup_mutex);
+static LIST_HEAD(nvmem_lookup_list);
+
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 static struct lock_class_key eeprom_lock_key;
 #endif
@@ -283,6 +286,18 @@ static struct nvmem_device *of_nvmem_find(struct device_node *nvmem_np)
 	return to_nvmem_device(d);
 }
 
+static struct nvmem_device *nvmem_find(const char *name)
+{
+	struct device *d;
+
+	d = bus_find_device_by_name(&nvmem_bus_type, NULL, name);
+
+	if (!d)
+		return NULL;
+
+	return to_nvmem_device(d);
+}
+
 static void nvmem_cell_drop(struct nvmem_cell *cell)
 {
 	mutex_lock(&nvmem_mutex);
@@ -472,6 +487,21 @@ nvmem_find_cell_by_index(struct nvmem_device *nvmem, int index)
 	return cell;
 }
 
+static struct nvmem_cell *
+nvmem_find_cell_by_name(struct nvmem_device *nvmem, const char *cell_id)
+{
+	struct nvmem_cell *cell = NULL;
+
+	mutex_lock(&nvmem_mutex);
+	list_for_each_entry(cell, &nvmem->cells, node) {
+		if (strcmp(cell_id, cell->name) == 0)
+			break;
+	}
+	mutex_unlock(&nvmem_mutex);
+
+	return cell;
+}
+
 static int nvmem_add_cells_from_of(struct nvmem_device *nvmem)
 {
 	struct device_node *parent, *child;
@@ -719,16 +749,12 @@ int devm_nvmem_unregister(struct device *dev, struct nvmem_device *nvmem)
 EXPORT_SYMBOL(devm_nvmem_unregister);
 
 static struct nvmem_device *__nvmem_device_get(struct device_node *np,
-					       struct nvmem_cell **cellp,
-					       const char *cell_id)
+					       const char *nvmem_name)
 {
 	struct nvmem_device *nvmem = NULL;
 
-	if (!np)
-		return ERR_PTR(-ENOENT);
-
 	mutex_lock(&nvmem_mutex);
-	nvmem = of_nvmem_find(np);
+	nvmem = np ? of_nvmem_find(np) : nvmem_find(nvmem_name);
 	mutex_unlock(&nvmem_mutex);
 	if (!nvmem)
 		return ERR_PTR(-EPROBE_DEFER);
@@ -752,18 +778,6 @@ static void __nvmem_device_put(struct nvmem_device *nvmem)
 	kref_put(&nvmem->refcnt, nvmem_device_release);
 }
 
-static struct nvmem_device *nvmem_find(const char *name)
-{
-	struct device *d;
-
-	d = bus_find_device_by_name(&nvmem_bus_type, NULL, name);
-
-	if (!d)
-		return ERR_PTR(-ENOENT);
-
-	return to_nvmem_device(d);
-}
-
 #if IS_ENABLED(CONFIG_OF)
 /**
  * of_nvmem_device_get() - Get nvmem device from a given id
@@ -786,7 +800,7 @@ struct nvmem_device *of_nvmem_device_get(struct device_node *np, const char *id)
 	if (!nvmem_np)
 		return ERR_PTR(-EINVAL);
 
-	return __nvmem_device_get(nvmem_np, NULL, NULL);
+	return __nvmem_device_get(nvmem_np, NULL);
 }
 EXPORT_SYMBOL_GPL(of_nvmem_device_get);
 #endif
@@ -890,15 +904,43 @@ struct nvmem_device *devm_nvmem_device_get(struct device *dev, const char *id)
 }
 EXPORT_SYMBOL_GPL(devm_nvmem_device_get);
 
-static struct nvmem_cell *nvmem_cell_get_from_list(const char *cell_id)
+static struct nvmem_cell *
+nvmem_cell_get_from_lookup(struct device *dev, const char *con_id)
 {
-	struct nvmem_cell *cell = NULL;
+	struct nvmem_cell *cell = ERR_PTR(-ENOENT);
+	struct nvmem_cell_lookup *lookup;
 	struct nvmem_device *nvmem;
+	const char *dev_id;
 
-	nvmem = __nvmem_device_get(NULL, &cell, cell_id);
-	if (IS_ERR(nvmem))
-		return ERR_CAST(nvmem);
+	if (!dev)
+		return ERR_PTR(-EINVAL);
+
+	dev_id = dev_name(dev);
+
+	mutex_lock(&nvmem_lookup_mutex);
+
+	list_for_each_entry(lookup, &nvmem_lookup_list, node) {
+		if ((strcmp(lookup->dev_id, dev_id) == 0) &&
+		    (strcmp(lookup->con_id, con_id) == 0)) {
+			/* This is the right entry. */
+			nvmem = __nvmem_device_get(NULL, lookup->nvmem_name);
+			if (!nvmem) {
+				/* Provider may not be registered yet. */
+				cell = ERR_PTR(-EPROBE_DEFER);
+				goto out;
+			}
+
+			cell = nvmem_find_cell_by_name(nvmem,
+						       lookup->cell_name);
+			if (!cell) {
+				__nvmem_device_put(nvmem);
+				goto out;
+			}
+		}
+	}
 
+out:
+	mutex_unlock(&nvmem_lookup_mutex);
 	return cell;
 }
 
@@ -935,7 +977,7 @@ struct nvmem_cell *of_nvmem_cell_get(struct device_node *np,
 	if (!nvmem_np)
 		return ERR_PTR(-EINVAL);
 
-	nvmem = __nvmem_device_get(nvmem_np, NULL, NULL);
+	nvmem = __nvmem_device_get(nvmem_np, NULL);
 	of_node_put(nvmem_np);
 	if (IS_ERR(nvmem))
 		return ERR_CAST(nvmem);
@@ -975,7 +1017,7 @@ struct nvmem_cell *nvmem_cell_get(struct device *dev, const char *cell_id)
 	if (!cell_id)
 		return ERR_PTR(-EINVAL);
 
-	return nvmem_cell_get_from_list(cell_id);
+	return nvmem_cell_get_from_lookup(dev, cell_id);
 }
 EXPORT_SYMBOL_GPL(nvmem_cell_get);
 
@@ -1405,6 +1447,41 @@ void nvmem_del_cell_table(struct nvmem_cell_table *table)
 }
 EXPORT_SYMBOL_GPL(nvmem_del_cell_table);
 
+/**
+ * nvmem_add_cell_lookups() - register a list of cell lookup entries
+ *
+ * @entries: array of cell lookup entries
+ * @nentries: number of cell lookup entries in the array
+ */
+void nvmem_add_cell_lookups(struct nvmem_cell_lookup *entries, size_t nentries)
+{
+	int i;
+
+	mutex_lock(&nvmem_lookup_mutex);
+	for (i = 0; i < nentries; i++)
+		list_add_tail(&entries[i].node, &nvmem_lookup_list);
+	mutex_unlock(&nvmem_lookup_mutex);
+}
+EXPORT_SYMBOL_GPL(nvmem_add_cell_lookups);
+
+/**
+ * nvmem_del_cell_lookups() - remove a list of previously added cell lookup
+ *                            entries
+ *
+ * @entries: array of cell lookup entries
+ * @nentries: number of cell lookup entries in the array
+ */
+void nvmem_del_cell_lookups(struct nvmem_cell_lookup *entries, size_t nentries)
+{
+	int i;
+
+	mutex_lock(&nvmem_lookup_mutex);
+	for (i = 0; i < nentries; i++)
+		list_del(&entries[i].node);
+	mutex_unlock(&nvmem_lookup_mutex);
+}
+EXPORT_SYMBOL_GPL(nvmem_del_cell_lookups);
+
 /**
  * nvmem_dev_name() - Get the name of a given nvmem device.
  *

include/linux/nvmem-consumer.h

@@ -29,6 +29,24 @@ struct nvmem_cell_info {
 	unsigned int		nbits;
 };
 
+/**
+ * struct nvmem_cell_lookup - cell lookup entry
+ *
+ * @nvmem_name:	Name of the provider.
+ * @cell_name:	Name of the nvmem cell as defined in the name field of
+ *		struct nvmem_cell_info.
+ * @dev_id:	Name of the consumer device that will be associated with
+ *		this cell.
+ * @con_id:	Connector id for this cell lookup.
+ */
+struct nvmem_cell_lookup {
+	const char		*nvmem_name;
+	const char		*cell_name;
+	const char		*dev_id;
+	const char		*con_id;
+	struct list_head	node;
+};
+
 #if IS_ENABLED(CONFIG_NVMEM)
 
 /* Cell based interface */
@@ -57,6 +75,11 @@ int nvmem_device_cell_write(struct nvmem_device *nvmem,
 
 const char *nvmem_dev_name(struct nvmem_device *nvmem);
 
+void nvmem_add_cell_lookups(struct nvmem_cell_lookup *entries,
+			    size_t nentries);
+void nvmem_del_cell_lookups(struct nvmem_cell_lookup *entries,
+			    size_t nentries);
+
 #else
 
 static inline struct nvmem_cell *nvmem_cell_get(struct device *dev,
@@ -151,6 +174,11 @@ static inline const char *nvmem_dev_name(struct nvmem_device *nvmem)
 	return NULL;
 }
 
+static inline void
+nvmem_add_cell_lookups(struct nvmem_cell_lookup *entries, size_t nentries) {}
+static inline void
+nvmem_del_cell_lookups(struct nvmem_cell_lookup *entries, size_t nentries) {}
+
 #endif /* CONFIG_NVMEM */
 
 #if IS_ENABLED(CONFIG_NVMEM) && IS_ENABLED(CONFIG_OF)