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From b6c217ab9be6895384cf0b284ace84ad79e5c53b Mon Sep 17 00:00:00 2001
From: Andrew Lunn <andrew@lunn.ch>
Date: Fri, 26 Feb 2016 20:59:19 +0100
Subject: nvmem: Add backwards compatibility support for older EEPROM drivers.

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@lunn.ch>
Acked-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/nvmem/core.c           | 84 ++++++++++++++++++++++++++++++++++++++----
 include/linux/nvmem-provider.h |  4 +-
 2 files changed, 79 insertions(+), 9 deletions(-)

--- 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;
@@ -56,16 +61,26 @@ static DEFINE_IDA(nvmem_ida);
 static LIST_HEAD(nvmem_cells);
 static DEFINE_MUTEX(nvmem_cells_mutex);
 
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+static struct lock_class_key eeprom_lock_key;
+#endif
+
 #define to_nvmem_device(d) container_of(d, struct nvmem_device, dev)
 
 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;
@@ -90,10 +105,16 @@ static ssize_t bin_attr_nvmem_write(stru
                                     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;
@@ -349,6 +370,43 @@ err:
        return rval;
 }
 
+/*
+ * nvmem_setup_compat() - Create an additional binary entry in
+ * drivers sys directory, to be backwards compatible with the older
+ * drivers/misc/eeprom drivers.
+ */
+static int nvmem_setup_compat(struct nvmem_device *nvmem,
+                             const struct nvmem_config *config)
+{
+       int rval;
+
+       if (!config->base_dev)
+               return -EINVAL;
+
+       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;
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+       nvmem->eeprom.attr.key = &eeprom_lock_key;
+#endif
+       nvmem->eeprom.private = &nvmem->dev;
+       nvmem->base_dev = config->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);
+               return rval;
+       }
+
+       nvmem->flags |= FLAG_COMPAT;
+
+       return 0;
+}
+
 /**
  * nvmem_register() - Register a nvmem device for given nvmem_config.
  * Also creates an binary entry in /sys/bus/nvmem/devices/dev-name/nvmem
@@ -416,16 +474,23 @@ struct nvmem_device *nvmem_register(cons
        dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", config->name);
 
        rval = device_add(&nvmem->dev);
-       if (rval) {
-               ida_simple_remove(&nvmem_ida, nvmem->id);
-               kfree(nvmem);
-               return ERR_PTR(rval);
+       if (rval)
+               goto out;
+
+       if (config->compat) {
+               rval = nvmem_setup_compat(nvmem, config);
+               if (rval)
+                       goto out;
        }
 
        if (config->cells)
                nvmem_add_cells(nvmem, config);
 
        return nvmem;
+out:
+       ida_simple_remove(&nvmem_ida, nvmem->id);
+       kfree(nvmem);
+       return ERR_PTR(rval);
 }
 EXPORT_SYMBOL_GPL(nvmem_register);
 
@@ -445,6 +510,9 @@ int nvmem_unregister(struct nvmem_device
        }
        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);
 
--- a/include/linux/nvmem-provider.h
+++ b/include/linux/nvmem-provider.h
@@ -24,6 +24,9 @@ struct nvmem_config {
        int                     ncells;
        bool                    read_only;
        bool                    root_only;
+       /* To be only used by old driver/misc/eeprom drivers */
+       bool                    compat;
+       struct device           *base_dev;
 };
 
 #if IS_ENABLED(CONFIG_NVMEM)
@@ -44,5 +47,4 @@ static inline int nvmem_unregister(struc
 }
 
 #endif /* CONFIG_NVMEM */
-
 #endif  /* ifndef _LINUX_NVMEM_PROVIDER_H */