[PATCH 2/5] nvmem: expose nvmem cells as cdev

[Marco Felsch]

Expose the nvmem cells via cdevs which is our equivalent to the Linux
sysfs exposure. This allows the easier user queries for board code and
shell. Keep the Linux function name scheme for
nvmem_populate_sysfs_cells() to reduce the diff for nvmem_register()
function.

Signed-off-by: Marco Felsch <m.felsch at pengutronix.de>
---
 drivers/nvmem/core.c | 109 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 109 insertions(+)

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index 657025daddb3..b4a29e4b67f3 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -44,6 +44,8 @@ struct nvmem_cell_entry {
 	struct device_node	*np;
 	struct nvmem_device	*nvmem;
 	struct list_head	node;
+
+	struct cdev		cdev;
 };
 
 struct nvmem_cell {
@@ -144,6 +146,107 @@ static struct nvmem_device *of_nvmem_find(struct device_node *nvmem_np)
 	return NULL;
 }
 
+static struct nvmem_cell *nvmem_create_cell(struct nvmem_cell_entry *entry,
+					    const char *id, int index);
+
+static ssize_t nvmem_cell_cdev_read(struct cdev *cdev, void *buf, size_t count,
+				    loff_t offset, unsigned long flags)
+{
+	struct nvmem_cell_entry *entry;
+	struct nvmem_cell *cell = NULL;
+	size_t cell_sz, read_len;
+	void *content;
+
+	entry = container_of(cdev, struct nvmem_cell_entry, cdev);
+	cell = nvmem_create_cell(entry, entry->name, 0);
+	if (IS_ERR(cell))
+		return PTR_ERR(cell);
+
+	if (!cell)
+		return -EINVAL;
+
+	content = nvmem_cell_read(cell, &cell_sz);
+	if (IS_ERR(content)) {
+		read_len = PTR_ERR(content);
+		goto destroy_cell;
+	}
+
+	read_len = min_t(unsigned int, cell_sz - offset, count);
+	memcpy(buf, content + offset, read_len);
+	kfree(content);
+
+destroy_cell:
+	kfree_const(cell->id);
+	kfree(cell);
+
+	return read_len;
+}
+
+static ssize_t nvmem_cell_cdev_write(struct cdev *cdev, const void *buf, size_t count,
+				     loff_t offset, unsigned long flags)
+{
+	struct nvmem_cell_entry *entry;
+	struct nvmem_cell *cell;
+	int ret;
+
+	entry = container_of(cdev, struct nvmem_cell_entry, cdev);
+
+	if (!entry->nvmem->reg_write)
+		return -EPERM;
+
+	if (offset >= entry->bytes)
+		return -EFBIG;
+
+	if (offset + count > entry->bytes)
+		count = entry->bytes - offset;
+
+	cell = nvmem_create_cell(entry, entry->name, 0);
+	if (IS_ERR(cell))
+		return PTR_ERR(cell);
+
+	if (!cell)
+		return -EINVAL;
+
+	ret = nvmem_cell_write(cell, buf, count);
+
+	kfree_const(cell->id);
+	kfree(cell);
+
+	return ret;
+}
+
+static struct cdev_operations nvmem_cell_chrdev_ops = {
+	.read  = nvmem_cell_cdev_read,
+	.write = nvmem_cell_cdev_write,
+};
+
+static int nvmem_populate_sysfs_cells(struct nvmem_device *nvmem)
+{
+	struct device *dev = &nvmem->dev;
+	struct nvmem_cell_entry *entry;
+
+	if (list_empty(&nvmem->cells))
+		return 0;
+
+	list_for_each_entry(entry, &nvmem->cells, node) {
+		struct cdev *cdev;
+		int ret;
+
+		cdev = &entry->cdev;
+		cdev->name = xasprintf("%s.%s", dev_name(dev),
+				       kbasename(entry->name));
+		cdev->ops = &nvmem_cell_chrdev_ops;
+		cdev->dev = dev;
+		cdev->size = entry->bytes;
+
+		ret = devfs_create(cdev);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
 static void nvmem_cell_entry_add(struct nvmem_cell_entry *cell)
 {
 	list_add_tail(&cell->node, &cell->nvmem->cells);
@@ -337,6 +440,12 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
 		}
 	}
 
+	rval = nvmem_populate_sysfs_cells(nvmem);
+	if (rval) {
+		kfree(nvmem);
+		return ERR_PTR(rval);
+	}
+
 	list_add_tail(&nvmem->node, &nvmem_devs);
 
 	return nvmem;
-- 
2.39.2