[PATCH 2/6] nvmem: Add backwards compatibility support for older EEPROM drivers.

[Andrew Lunn]

Older drivers made an 'eeprom' file available in the /sys device
directory. Have the NVMEM core provide this to retain backwards
compatibility.

Signed-off-by: Andrew Lunn <andrew@xxxxxxx>
---
 drivers/nvmem/Kconfig          |  7 ++++
 drivers/nvmem/core.c           | 75 +++++++++++++++++++++++++++++++++++++++---
 include/linux/nvmem-provider.h | 10 ++++++
 3 files changed, 88 insertions(+), 4 deletions(-)

diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
index bc4ea585b42e..b4e79ba7d502 100644
--- a/drivers/nvmem/Kconfig
+++ b/drivers/nvmem/Kconfig
@@ -13,6 +13,13 @@ menuconfig NVMEM
 	  If unsure, say no.
 
 if NVMEM
+config NVMEM_COMPAT
+       bool "Enable /sys compatibility with old eeprom drivers"
+       help
+	 Older EEPROM drivers, such as AT24, AT25, provide access to
+	 the eeprom via a file called "eeprom" in /sys under the
+	 device node. Enabling this option makes the NVMEM core
+	 provide this file to retain backwards compatibility
 
 config NVMEM_IMX_OCOTP
 	tristate "i.MX6 On-Chip OTP Controller support"
diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index 4ccf03da6467..75a498f5e139 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -38,8 +38,13 @@ struct nvmem_device {
 	int			users;
 	size_t			size;
 	bool			read_only;
+	int			flags;
+	struct bin_attribute	eeprom;
+	struct device		*base_dev;
 };
 
+#define FLAG_COMPAT		BIT(0)
+
 struct nvmem_cell {
 	const char		*name;
 	int			offset;
@@ -62,10 +67,16 @@ static ssize_t bin_attr_nvmem_read(struct file *filp, struct kobject *kobj,
 				    struct bin_attribute *attr,
 				    char *buf, loff_t pos, size_t count)
 {
-	struct device *dev = container_of(kobj, struct device, kobj);
-	struct nvmem_device *nvmem = to_nvmem_device(dev);
+	struct device *dev;
+	struct nvmem_device *nvmem;
 	int rc;
 
+	if (attr->private)
+		dev = attr->private;
+	else
+		dev = container_of(kobj, struct device, kobj);
+	nvmem = to_nvmem_device(dev);
+
 	/* Stop the user from reading */
 	if (pos >= nvmem->size)
 		return 0;
@@ -87,10 +98,16 @@ static ssize_t bin_attr_nvmem_write(struct file *filp, struct kobject *kobj,
 				     struct bin_attribute *attr,
 				     char *buf, loff_t pos, size_t count)
 {
-	struct device *dev = container_of(kobj, struct device, kobj);
-	struct nvmem_device *nvmem = to_nvmem_device(dev);
+	struct device *dev;
+	struct nvmem_device *nvmem;
 	int rc;
 
+	if (attr->private)
+		dev = attr->private;
+	else
+		dev = container_of(kobj, struct device, kobj);
+	nvmem = to_nvmem_device(dev);
+
 	/* Stop the user from writing */
 	if (pos >= nvmem->size)
 		return 0;
@@ -421,6 +438,53 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
 }
 EXPORT_SYMBOL_GPL(nvmem_register);
 
+#if IS_ENABLED(CONFIG_NVMEM_COMPAT)
+/**
+ * nvmem_register_compat() - Register a nvmem device for given nvmem_config.
+ * Also creates an binary entry in /sys/bus/nvmem/devices/dev-name/nvmem and
+ * an eeprom file in the drivers sys directory.
+ *
+ * @config: nvmem device configuration with which nvmem device is created.
+ * @dev: device structure of underlying device
+ *
+ * Return: Will be an ERR_PTR() on error or a valid pointer to nvmem_device
+ * on success.
+ */
+
+struct nvmem_device *nvmem_register_compat(const struct nvmem_config *config,
+					   struct device *base_dev)
+{
+	struct nvmem_device *nvmem;
+	int rval;
+
+	nvmem = nvmem_register(config);
+	if (IS_ERR(nvmem))
+		return nvmem;
+
+	if (nvmem->read_only)
+		nvmem->eeprom = bin_attr_ro_root_nvmem;
+	else
+		nvmem->eeprom = bin_attr_rw_root_nvmem;
+	nvmem->eeprom.attr.name = "eeprom";
+	nvmem->eeprom.size = nvmem->size;
+	nvmem->eeprom.private = &nvmem->dev;
+	nvmem->base_dev = base_dev;
+
+	rval = device_create_bin_file(nvmem->base_dev, &nvmem->eeprom);
+	if (rval) {
+		dev_err(&nvmem->dev,
+			"Failed to create eeprom binary file %d\n", rval);
+		nvmem_unregister(nvmem);
+		return ERR_PTR(rval);
+	}
+
+	nvmem->flags |= FLAG_COMPAT;
+
+	return nvmem;
+}
+EXPORT_SYMBOL_GPL(nvmem_register_compat);
+#endif /* CONFIG_NVMEM_COMPAT */
+
 /**
  * nvmem_unregister() - Unregister previously registered nvmem device
  *
@@ -437,6 +501,9 @@ int nvmem_unregister(struct nvmem_device *nvmem)
 	}
 	mutex_unlock(&nvmem_mutex);
 
+	if (nvmem->flags & FLAG_COMPAT)
+		device_remove_bin_file(nvmem->base_dev, &nvmem->eeprom);
+
 	nvmem_device_remove_all_cells(nvmem);
 	device_del(&nvmem->dev);
 
diff --git a/include/linux/nvmem-provider.h b/include/linux/nvmem-provider.h
index d24fefa0c11d..012030bd4495 100644
--- a/include/linux/nvmem-provider.h
+++ b/include/linux/nvmem-provider.h
@@ -45,4 +45,14 @@ static inline int nvmem_unregister(struct nvmem_device *nvmem)
 
 #endif /* CONFIG_NVMEM */
 
+#if IS_ENABLED(CONFIG_NVMEM) && IS_ENABLED(CONFIG_NVMEM_COMPAT)
+struct nvmem_device *nvmem_register_compat(const struct nvmem_config *config,
+					   struct device *base_dev);
+#else
+static inline struct nvmem_device *
+nvmem_register_compat(const struct nvmem_config *c, struct device *base_dev)
+{
+	return ERR_PTR(-ENOSYS);
+}
+#endif  /* CONFIG_NVMEM && CONFIG_NVMEM_COMPAT */
 #endif  /* ifndef _LINUX_NVMEM_PROVIDER_H */
-- 
2.6.2

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