nvmem: core: introduce NVMEM layouts

NVMEM layouts are used to generate NVMEM cells during runtime. Think of
an EEPROM with a well-defined conent. For now, the content can be
described by a device tree or a board file. But this only works if the
offsets and lengths are static and don't change. One could also argue
that putting the layout of the EEPROM in the device tree is the wrong
place. Instead, the device tree should just have a specific compatible
string.

Right now there are two use cases:
 (1) The NVMEM cell needs special processing. E.g. if it only specifies
     a base MAC address offset and you need to add an offset, or it
     needs to parse a MAC from ASCII format or some proprietary format.
     (Post processing of cells is added in a later commit).
 (2) u-boot environment parsing. The cells don't have a particular
     offset but it needs parsing the content to determine the offsets
     and length.

Co-developed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20230404172148.82422-14-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 51 insertions, 0 deletions

diff --git a/include/linux/nvmem-provider.h b/include/linux/nvmem-provider.h
index 0262b86194eb..535c5f9f3309 100644
--- a/include/linux/nvmem-provider.h
+++ b/include/linux/nvmem-provider.h
@@ -88,6 +88,7 @@ struct nvmem_cell_info {
  * @stride:	Minimum read/write access stride.
  * @priv:	User context passed to read/write callbacks.
  * @ignore_wp:  Write Protect pin is managed by the provider.
+ * @layout:	Fixed layout associated with this nvmem device.
  *
  * Note: A default "nvmem<id>" name will be assigned to the device if
  * no name is specified in its configuration. In such case "<id>" is
@@ -109,6 +110,7 @@ struct nvmem_config {
 	bool			read_only;
 	bool			root_only;
 	bool			ignore_wp;
+	struct nvmem_layout	*layout;
 	struct device_node	*of_node;
 	bool			no_of_node;
 	nvmem_reg_read_t	reg_read;
@@ -142,6 +144,33 @@ struct nvmem_cell_table {
 	struct list_head	node;
 };
 
+/**
+ * struct nvmem_layout - NVMEM layout definitions
+ *
+ * @name:		Layout name.
+ * @of_match_table:	Open firmware match table.
+ * @add_cells:		Will be called if a nvmem device is found which
+ *			has this layout. The function will add layout
+ *			specific cells with nvmem_add_one_cell().
+ * @owner:		Pointer to struct module.
+ * @node:		List node.
+ *
+ * A nvmem device can hold a well defined structure which can just be
+ * evaluated during runtime. For example a TLV list, or a list of "name=val"
+ * pairs. A nvmem layout can parse the nvmem device and add appropriate
+ * cells.
+ */
+struct nvmem_layout {
+	const char *name;
+	const struct of_device_id *of_match_table;
+	int (*add_cells)(struct device *dev, struct nvmem_device *nvmem,
+			 struct nvmem_layout *layout);
+
+	/* private */
+	struct module *owner;
+	struct list_head node;
+};
+
 #if IS_ENABLED(CONFIG_NVMEM)
 
 struct nvmem_device *nvmem_register(const struct nvmem_config *cfg);
@@ -156,6 +185,14 @@ void nvmem_del_cell_table(struct nvmem_cell_table *table);
 int nvmem_add_one_cell(struct nvmem_device *nvmem,
 		       const struct nvmem_cell_info *info);
 
+int __nvmem_layout_register(struct nvmem_layout *layout, struct module *owner);
+#define nvmem_layout_register(layout) \
+	__nvmem_layout_register(layout, THIS_MODULE)
+void nvmem_layout_unregister(struct nvmem_layout *layout);
+
+const void *nvmem_layout_get_match_data(struct nvmem_device *nvmem,
+					struct nvmem_layout *layout);
+
 #else
 
 static inline struct nvmem_device *nvmem_register(const struct nvmem_config *c)
@@ -179,5 +216,19 @@ static inline int nvmem_add_one_cell(struct nvmem_device *nvmem,
 	return -EOPNOTSUPP;
 }
 
+static inline int nvmem_layout_register(struct nvmem_layout *layout)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline void nvmem_layout_unregister(struct nvmem_layout *layout) {}
+
+static inline const void *
+nvmem_layout_get_match_data(struct nvmem_device *nvmem,
+			    struct nvmem_layout *layout)
+{
+	return NULL;
+}
+
 #endif /* CONFIG_NVMEM */
 #endif  /* ifndef _LINUX_NVMEM_PROVIDER_H */