[PATCH 3/8] nvmem: Add nvmem_cell_get_optional and devm_nvmem_cell_get_optional

[Alban Bedel <albeu@free.fr>]

Add helper functions to make the driver code simpler when a cell is
optional. Using these functions just return NULL when the cell doesn't
exists or if nvmem is disabled.

Signed-off-by: Alban Bedel <albeu@free.fr>
---
 drivers/nvmem/core.c           | 48 ++++++++++++++++++++++++++++++++++
 include/linux/nvmem-consumer.h | 16 ++++++++++++
 2 files changed, 64 insertions(+)

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index f8c43da6f2ca..8e1b52559467 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -1083,6 +1083,30 @@ struct nvmem_cell *nvmem_cell_get(struct device *dev, const char *id)
 }
 EXPORT_SYMBOL_GPL(nvmem_cell_get);
 
+/**
+ * nvmem_cell_get_optional() - Get an optional nvmem cell of device from
+ * a given id.
+ *
+ * @dev: Device that requests the nvmem cell.
+ * @cell_id: nvmem cell name to get.
+ *
+ * Return: Will be NULL if no cell with the given name is defined,
+ * an ERR_PTR() on error or a valid pointer to a struct nvmem_cell.
+ * The nvmem_cell will be freed by the nvmem_cell_put().
+ */
+struct nvmem_cell *nvmem_cell_get_optional(struct device *dev,
+					   const char *cell_id)
+{
+	struct nvmem_cell *cell;
+
+	cell = nvmem_cell_get(dev, cell_id);
+	if (IS_ERR(cell) && PTR_ERR(cell) == -ENOENT)
+		return NULL;
+
+	return cell;
+}
+EXPORT_SYMBOL_GPL(nvmem_cell_get_optional);
+
 static void devm_nvmem_cell_release(struct device *dev, void *res)
 {
 	nvmem_cell_put(*(struct nvmem_cell **)res);
@@ -1118,6 +1142,30 @@ struct nvmem_cell *devm_nvmem_cell_get(struct device *dev, const char *id)
 }
 EXPORT_SYMBOL_GPL(devm_nvmem_cell_get);
 
+/**
+ * devm_nvmem_cell_get() - Get an optional nvmem cell of device from
+ * a given id.
+ *
+ * @dev: Device that requests the nvmem cell.
+ * @id: nvmem cell name id to get.
+ *
+ * Return: Will be NULL if the cell doesn't exists, an ERR_PTR() on
+ * error or a valid pointer to a struct nvmem_cell.  The nvmem_cell
+ * will be freed by the automatically once the device is freed.
+ */
+struct nvmem_cell *devm_nvmem_cell_get_optional(struct device *dev,
+						const char *cell_id)
+{
+	struct nvmem_cell *cell;
+
+	cell = devm_nvmem_cell_get(dev, cell_id);
+	if (IS_ERR(cell) && PTR_ERR(cell) == -ENOENT)
+		return NULL;
+
+	return cell;
+}
+EXPORT_SYMBOL_GPL(devm_nvmem_cell_get_optional);
+
 static int devm_nvmem_cell_match(struct device *dev, void *res, void *data)
 {
 	struct nvmem_cell **c = res;
diff --git a/include/linux/nvmem-consumer.h b/include/linux/nvmem-consumer.h
index 312bfa5efd80..8d7bf21a9adc 100644
--- a/include/linux/nvmem-consumer.h
+++ b/include/linux/nvmem-consumer.h
@@ -56,7 +56,11 @@ enum {
 
 /* Cell based interface */
 struct nvmem_cell *nvmem_cell_get(struct device *dev, const char *id);
+struct nvmem_cell *nvmem_cell_get_optional(struct device *dev,
+					   const char *id);
 struct nvmem_cell *devm_nvmem_cell_get(struct device *dev, const char *id);
+struct nvmem_cell *devm_nvmem_cell_get_optional(struct device *dev,
+						const char *id);
 void nvmem_cell_put(struct nvmem_cell *cell);
 void devm_nvmem_cell_put(struct device *dev, struct nvmem_cell *cell);
 void *nvmem_cell_read(struct nvmem_cell *cell, size_t *len);
@@ -96,12 +100,24 @@ static inline struct nvmem_cell *nvmem_cell_get(struct device *dev,
 	return ERR_PTR(-EOPNOTSUPP);
 }
 
+static inline struct nvmem_cell *nvmem_cell_get_optional(struct device *dev,
+							 const char *id)
+{
+	return NULL;
+}
+
 static inline struct nvmem_cell *devm_nvmem_cell_get(struct device *dev,
 						     const char *id)
 {
 	return ERR_PTR(-EOPNOTSUPP);
 }
 
+static inline struct nvmem_cell *
+devm_nvmem_cell_get_optional(struct device *dev, const char *id)
+{
+	return NULL;
+}
+
 static inline void devm_nvmem_cell_put(struct device *dev,
 				       struct nvmem_cell *cell)
 {
-- 
2.19.1