[RFC 3/3] nvmem: Add 'nvmem-composite' driver

[Andrey Smirnov]

Add 'nvmem-composite' driver which allows to combine multiple chunks of
various NVMEM cells into a single continuous NVMEM device.

Signed-off-by: Andrey Smirnov <andrew.smirnov@xxxxxxxxx>
---
 .../devicetree/bindings/nvmem/composite.txt        |  44 ++++
 drivers/nvmem/Makefile                             |   1 +
 drivers/nvmem/composite.c                          | 228 +++++++++++++++++++++
 3 files changed, 273 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/nvmem/composite.txt
 create mode 100644 drivers/nvmem/composite.c

diff --git a/Documentation/devicetree/bindings/nvmem/composite.txt b/Documentation/devicetree/bindings/nvmem/composite.txt
new file mode 100644
index 0000000..e24cf4b
--- /dev/null
+++ b/Documentation/devicetree/bindings/nvmem/composite.txt
@@ -0,0 +1,44 @@
+= NVMEM cell compositor =
+
+This binding is designed to provide a way for a developer to combine
+portions of other NVMEM cell and acces that data as a signle NVMEM
+cell using NVMEM consumer API.
+
+Required properties:
+- compatible: should be "nvmem-composite"
+- layout: specifies which sources comprise data in nvmem device
+  	  format is "<nvmem-cell-phandle offset size>"
+
+= Data cells =
+Are child nodes of nvmem-composite, bindings of which as described in
+bindings/nvmem/nvmem.txt
+
+Example:
+
+	composite-nvmem {
+		compatible = "nvmem-composite";
+		layout = <&another_cell_a 0 2
+ 			  &another_cell_b 0 1
+			  &another_cell_c 3 2>;
+
+		cell1: cell@0 {
+			reg = <0 5>;
+		};
+	}
+
+the result of reading variable cell1 would be:
+
+[a[0] a[1] b[0] c[3] c[4]],
+
+where a[i], b[i], c[i], represnet i-th bytes of NVMEM cells
+another_cell_a, another_cell_b and another_cell_c respectively
+
+= Data consumers =
+Are device nodes which consume nvmem data cells.
+
+Example:
+
+	a-node {
+		nvmem-cells = <&cell1>;
+		nvmem-cell-names = "some-data";
+	};
diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
index 1a1adba..49c0eca 100644
--- a/drivers/nvmem/Makefile
+++ b/drivers/nvmem/Makefile
@@ -19,3 +19,4 @@ nvmem_sunxi_sid-y		:= sunxi_sid.o
 obj-$(CONFIG_NVMEM_VF610_OCOTP)	+= nvmem-vf610-ocotp.o
 nvmem-vf610-ocotp-y		:= vf610-ocotp.o
 obj-y += blob.o
+obj-y += composite.o
diff --git a/drivers/nvmem/composite.c b/drivers/nvmem/composite.c
new file mode 100644
index 0000000..5c29923
--- /dev/null
+++ b/drivers/nvmem/composite.c
@@ -0,0 +1,228 @@
+#define DEBUG 1
+
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/nvmem-consumer.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+struct nvmem_composite {
+	struct device *dev;
+	struct list_head layout;
+	size_t layout_size;
+};
+
+struct nvmem_composite_item {
+	struct nvmem_cell *cell;
+	unsigned int idx, start, end, size;
+	struct list_head node;
+};
+
+static struct nvmem_composite_item *
+nvmem_composite_find_first(struct nvmem_composite *ncomp,
+			   unsigned int offset)
+{
+	struct nvmem_composite_item *first;
+	list_for_each_entry(first, &ncomp->layout, node) {
+		/* 
+		 * Skip all of the irrelevant items that end before our offset
+		 */
+		if (first->end > offset)
+			return first;
+	}
+
+	return NULL;
+}
+
+static int nvmem_composite_read(void *context,
+				const void *reg, size_t reg_size,
+				void *val, size_t val_size)
+{
+	int ii;
+	struct nvmem_composite *ncomp = context;
+	const unsigned int offset = *(u32 *)reg;
+	void *dst = val;
+	size_t residue = val_size;
+	struct nvmem_composite_item *item, *first;
+	uint8_t *data;
+	size_t size, chunk;
+
+
+	first = item = nvmem_composite_find_first(ncomp, offset);
+	if (!first) {
+		dev_dbg(ncomp->dev, "Invalid offset\n");
+		return -EINVAL;
+	}
+
+	list_for_each_entry_from(item, &ncomp->layout, node) {
+		/* 
+		 * If our first read is not located on item boundary
+		 * we have to introduce artificial offset
+		 */
+		ii = (item == first) ? offset - first->start : 0;
+
+		data = nvmem_cell_read(item->cell, &size);
+		if (IS_ERR(data)) {
+			dev_dbg(ncomp->dev, "Failed to read nvmem cell\n");
+			return PTR_ERR(data);
+		}
+
+		chunk = min(residue, item->size - ii);
+		memcpy(dst, &data[item->idx + ii], chunk);
+		kfree(data);
+
+		dev_dbg(ncomp->dev, "chunk %u\n", chunk);
+
+		dst += chunk;
+		residue -= chunk;
+	}
+
+	return (residue) ? -EINVAL : 0;
+}
+
+static int nvmem_composite_write(void *context, const void *data,
+				 size_t count)
+{
+	return -ENOTSUPP;
+}
+
+static const struct regmap_bus nvmem_composite_regmap_bus = {
+	.write = nvmem_composite_write,
+	.read  = nvmem_composite_read,
+};
+
+static int nvmem_composite_validate_dt(struct device_node *np)
+{
+	/* FIXME */
+	return 0;
+}
+
+static int nvmem_composite_probe(struct platform_device *pdev)
+{
+	int i, ret;
+	unsigned int start = 0;
+	unsigned int len;
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	struct nvmem_device *nvmem;
+	struct nvmem_composite *ncomp;
+	struct regmap *map;
+	struct nvmem_composite_item *item;
+	struct nvmem_config  nv_cnf = {0};
+	struct regmap_config rm_cnf = {0};
+	const __be32 *addr;
+	unsigned int item_count;
+
+	ret = nvmem_composite_validate_dt(np);
+	if (ret < 0) {
+		dev_dbg(dev, "Device validation failed\n");
+		return ret;
+	}
+
+	ncomp = devm_kzalloc(dev, sizeof(*ncomp), GFP_KERNEL);
+	INIT_LIST_HEAD(&ncomp->layout);
+	ncomp->dev = dev;
+	
+	addr = of_get_property(np, "layout", &len);
+	item_count = len / (3 * sizeof(__be32));
+
+	for (i = 0; i < item_count; i++) {
+		struct device_node *cell_np;
+		uint32_t phandle;
+
+		item = devm_kzalloc(dev, sizeof(*item), GFP_KERNEL);
+
+		phandle = be32_to_cpup(addr++);
+		cell_np = of_find_node_by_phandle(phandle);
+		if (!cell_np) {
+			dev_dbg(dev,
+				"Couldn't find nvmem cell by its phandle\n");
+			return -ENOENT;
+		}
+
+		item->cell = of_nvmem_cell_from_device_node(cell_np);
+		if (IS_ERR(item->cell)) {
+			dev_dbg(dev,
+				"Failed to instantiate nvmem cell from "
+				"a device tree node\n");
+			ret = PTR_ERR(item->cell);
+			goto unwind;
+		}
+
+		item->start = start;
+		item->idx = be32_to_cpup(addr++);
+		item->size = be32_to_cpup(addr++);
+		item->end  = item->size - 1;
+		ncomp->layout_size += item->size;
+		start += item->size;
+
+		list_add_tail(&item->node, &ncomp->layout);
+	}
+
+	rm_cnf.reg_bits = 32;
+	rm_cnf.val_bits = 8;
+	rm_cnf.reg_stride = 1;
+	rm_cnf.name = "nvmem-composite";
+	rm_cnf.max_register = ncomp->layout_size - 1;
+
+	map = devm_regmap_init(dev,
+			       &nvmem_composite_regmap_bus,
+			       ncomp,
+			       &rm_cnf);
+	if (IS_ERR(map)) {
+		dev_dbg(dev, "Failed to initilize regmap\n");
+		return PTR_ERR(map);
+	}
+
+	nv_cnf.name = "nvmem-composite";
+	nv_cnf.read_only = true;
+	nv_cnf.dev = dev;
+
+	nvmem = nvmem_register(&nv_cnf);
+	if (IS_ERR(nvmem)) {
+		dev_dbg(dev, "Failed to register 'nvmem' device\n");
+		return PTR_ERR(nvmem);
+	}
+
+	platform_set_drvdata(pdev, nvmem);
+	return 0;
+unwind:
+	/* FIXME  */
+	return ret;
+}
+
+static int nvmem_composite_remove(struct platform_device *pdev)
+{
+	struct nvmem_device *nvmem = platform_get_drvdata(pdev);
+
+	/* 
+	   FIXME free allocated nvmem cells
+	 */
+	return nvmem_unregister(nvmem);
+}
+
+
+static const struct of_device_id nvmem_composite_dt_ids[] = {
+	{ .compatible = "nvmem-composite", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, nvmem_composite_dt_ids);
+
+static struct platform_driver nvmem_composite_driver = {
+	.probe	= nvmem_composite_probe,
+	.remove	= nvmem_composite_remove,
+	.driver = {
+		.name	= "nvmem-composite",
+		.of_match_table = nvmem_composite_dt_ids,
+	},
+};
+module_platform_driver(nvmem_composite_driver);
+
+MODULE_AUTHOR("Andrey Smirnov <andrew.smirnov@xxxxxxxxx>");
+MODULE_DESCRIPTION("FIXME");
+MODULE_LICENSE("GPL v2");
-- 
2.5.0