From 5d8e6e6c10a3d37486d263b16ddc15991a7e4a88 Mon Sep 17 00:00:00 2001
From: Michael Walle <michael@walle.cc>
Date: Mon, 6 Feb 2023 13:43:46 +0000
Subject: [PATCH] nvmem: core: add an index parameter to the cell

Sometimes a cell can represend multiple values. For example, a base
ethernet address stored in the NVMEM can be expanded into multiple
discreet ones by adding an offset.

For this use case, introduce an index parameter which is then used to
distiguish between values. This parameter will then be passed to the
post process hook which can then use it to create different values
during reading.

At the moment, there is only support for the device tree path. You can
add the index to the phandle, e.g.

  &net {
          nvmem-cells = <&base_mac_address 2>;
          nvmem-cell-names = "mac-address";
  };

  &nvmem_provider {
          base_mac_address: base-mac-address@0 {
                  #nvmem-cell-cells = <1>;
                  reg = <0 6>;
          };
  };

Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20230206134356.839737-13-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/nvmem/core.c           | 37 ++++++++++++++++++++++++----------
 drivers/nvmem/imx-ocotp.c      |  4 ++--
 include/linux/nvmem-provider.h |  4 ++--
 3 files changed, 30 insertions(+), 15 deletions(-)

--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -60,6 +60,7 @@ struct nvmem_cell_entry {
 struct nvmem_cell {
 	struct nvmem_cell_entry *entry;
 	const char		*id;
+	int			index;
 };
 
 static DEFINE_MUTEX(nvmem_mutex);
@@ -1122,7 +1123,8 @@ struct nvmem_device *devm_nvmem_device_g
 }
 EXPORT_SYMBOL_GPL(devm_nvmem_device_get);
 
-static struct nvmem_cell *nvmem_create_cell(struct nvmem_cell_entry *entry, const char *id)
+static struct nvmem_cell *nvmem_create_cell(struct nvmem_cell_entry *entry,
+					    const char *id, int index)
 {
 	struct nvmem_cell *cell;
 	const char *name = NULL;
@@ -1141,6 +1143,7 @@ static struct nvmem_cell *nvmem_create_c
 
 	cell->id = name;
 	cell->entry = entry;
+	cell->index = index;
 
 	return cell;
 }
@@ -1179,7 +1182,7 @@ nvmem_cell_get_from_lookup(struct device
 				__nvmem_device_put(nvmem);
 				cell = ERR_PTR(-ENOENT);
 			} else {
-				cell = nvmem_create_cell(cell_entry, con_id);
+				cell = nvmem_create_cell(cell_entry, con_id, 0);
 				if (IS_ERR(cell))
 					__nvmem_device_put(nvmem);
 			}
@@ -1227,15 +1230,27 @@ struct nvmem_cell *of_nvmem_cell_get(str
 	struct nvmem_device *nvmem;
 	struct nvmem_cell_entry *cell_entry;
 	struct nvmem_cell *cell;
+	struct of_phandle_args cell_spec;
 	int index = 0;
+	int cell_index = 0;
+	int ret;
 
 	/* if cell name exists, find index to the name */
 	if (id)
 		index = of_property_match_string(np, "nvmem-cell-names", id);
 
-	cell_np = of_parse_phandle(np, "nvmem-cells", index);
-	if (!cell_np)
-		return ERR_PTR(-ENOENT);
+	ret = of_parse_phandle_with_optional_args(np, "nvmem-cells",
+						  "#nvmem-cell-cells",
+						  index, &cell_spec);
+	if (ret)
+		return ERR_PTR(ret);
+
+	if (cell_spec.args_count > 1)
+		return ERR_PTR(-EINVAL);
+
+	cell_np = cell_spec.np;
+	if (cell_spec.args_count)
+		cell_index = cell_spec.args[0];
 
 	nvmem_np = of_get_parent(cell_np);
 	if (!nvmem_np) {
@@ -1257,7 +1272,7 @@ struct nvmem_cell *of_nvmem_cell_get(str
 		return ERR_PTR(-ENOENT);
 	}
 
-	cell = nvmem_create_cell(cell_entry, id);
+	cell = nvmem_create_cell(cell_entry, id, cell_index);
 	if (IS_ERR(cell))
 		__nvmem_device_put(nvmem);
 
@@ -1410,8 +1425,8 @@ static void nvmem_shift_read_buffer_in_p
 }
 
 static int __nvmem_cell_read(struct nvmem_device *nvmem,
-		      struct nvmem_cell_entry *cell,
-		      void *buf, size_t *len, const char *id)
+			     struct nvmem_cell_entry *cell,
+			     void *buf, size_t *len, const char *id, int index)
 {
 	int rc;
 
@@ -1425,7 +1440,7 @@ static int __nvmem_cell_read(struct nvme
 		nvmem_shift_read_buffer_in_place(cell, buf);
 
 	if (nvmem->cell_post_process) {
-		rc = nvmem->cell_post_process(nvmem->priv, id,
+		rc = nvmem->cell_post_process(nvmem->priv, id, index,
 					      cell->offset, buf, cell->bytes);
 		if (rc)
 			return rc;
@@ -1460,7 +1475,7 @@ void *nvmem_cell_read(struct nvmem_cell
 	if (!buf)
 		return ERR_PTR(-ENOMEM);
 
-	rc = __nvmem_cell_read(nvmem, cell->entry, buf, len, cell->id);
+	rc = __nvmem_cell_read(nvmem, cell->entry, buf, len, cell->id, cell->index);
 	if (rc) {
 		kfree(buf);
 		return ERR_PTR(rc);
@@ -1773,7 +1788,7 @@ ssize_t nvmem_device_cell_read(struct nv
 	if (rc)
 		return rc;
 
-	rc = __nvmem_cell_read(nvmem, &cell, buf, &len, NULL);
+	rc = __nvmem_cell_read(nvmem, &cell, buf, &len, NULL, 0);
 	if (rc)
 		return rc;
 
--- a/drivers/nvmem/imx-ocotp.c
+++ b/drivers/nvmem/imx-ocotp.c
@@ -222,8 +222,8 @@ read_end:
 	return ret;
 }
 
-static int imx_ocotp_cell_pp(void *context, const char *id, unsigned int offset,
-			     void *data, size_t bytes)
+static int imx_ocotp_cell_pp(void *context, const char *id, int index,
+			     unsigned int offset, void *data, size_t bytes)
 {
 	struct ocotp_priv *priv = context;
 
--- a/include/linux/nvmem-provider.h
+++ b/include/linux/nvmem-provider.h
@@ -20,8 +20,8 @@ typedef int (*nvmem_reg_read_t)(void *pr
 typedef int (*nvmem_reg_write_t)(void *priv, unsigned int offset,
 				 void *val, size_t bytes);
 /* used for vendor specific post processing of cell data */
-typedef int (*nvmem_cell_post_process_t)(void *priv, const char *id, unsigned int offset,
-					  void *buf, size_t bytes);
+typedef int (*nvmem_cell_post_process_t)(void *priv, const char *id, int index,
+					 unsigned int offset, void *buf, size_t bytes);
 
 enum nvmem_type {
 	NVMEM_TYPE_UNKNOWN = 0,
