nvmem: use kref

Use kref for reference counting. Use an approach similar to the one
seen in the common clock subsystem: don't actually destroy the nvmem
device until the last user puts it. This way we can get rid of the
users check from nvmem_unregister().

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index 0ef8444..920b56e 100644 (file)
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -19,6 +19,7 @@
 #include <linux/fs.h>
 #include <linux/idr.h>
 #include <linux/init.h>
+#include <linux/kref.h>
 #include <linux/module.h>
 #include <linux/nvmem-consumer.h>
 #include <linux/nvmem-provider.h>
@@ -31,7 +32,7 @@ struct nvmem_device {
        int                     stride;
        int                     word_size;
        int                     id;
-       int                     users;
+       struct kref             refcnt;
        size_t                  size;
        bool                    read_only;
        int                     flags;
@@ -463,6 +464,8 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
                return ERR_PTR(rval);
        }
 
+       kref_init(&nvmem->refcnt);
+
        nvmem->id = rval;
        nvmem->owner = config->owner;
        if (!nvmem->owner && config->dev->driver)
@@ -532,6 +535,20 @@ err_put_device:
 }
 EXPORT_SYMBOL_GPL(nvmem_register);
 
+static void nvmem_device_release(struct kref *kref)
+{
+       struct nvmem_device *nvmem;
+
+       nvmem = container_of(kref, struct nvmem_device, refcnt);
+
+       if (nvmem->flags & FLAG_COMPAT)
+               device_remove_bin_file(nvmem->base_dev, &nvmem->eeprom);
+
+       nvmem_device_remove_all_cells(nvmem);
+       device_del(&nvmem->dev);
+       put_device(&nvmem->dev);
+}
+
 /**
  * nvmem_unregister() - Unregister previously registered nvmem device
  *
@@ -541,19 +558,7 @@ EXPORT_SYMBOL_GPL(nvmem_register);
  */
 int nvmem_unregister(struct nvmem_device *nvmem)
 {
-       mutex_lock(&nvmem_mutex);
-       if (nvmem->users) {
-               mutex_unlock(&nvmem_mutex);
-               return -EBUSY;
-       }
-       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);
-       put_device(&nvmem->dev);
+       kref_put(&nvmem->refcnt, nvmem_device_release);
 
        return 0;
 }
@@ -647,7 +652,6 @@ static struct nvmem_device *__nvmem_device_get(struct device_node *np,
                }
        }
 
-       nvmem->users++;
        mutex_unlock(&nvmem_mutex);
 
        if (!try_module_get(nvmem->owner)) {
@@ -655,22 +659,18 @@ static struct nvmem_device *__nvmem_device_get(struct device_node *np,
                        "could not increase module refcount for cell %s\n",
                        nvmem_dev_name(nvmem));
 
-               mutex_lock(&nvmem_mutex);
-               nvmem->users--;
-               mutex_unlock(&nvmem_mutex);
-
                return ERR_PTR(-EINVAL);
        }
 
+       kref_get(&nvmem->refcnt);
+
        return nvmem;
 }
 
 static void __nvmem_device_put(struct nvmem_device *nvmem)
 {
        module_put(nvmem->owner);
-       mutex_lock(&nvmem_mutex);
-       nvmem->users--;
-       mutex_unlock(&nvmem_mutex);
+       kref_put(&nvmem->refcnt, nvmem_device_release);
 }
 
 static struct nvmem_device *nvmem_find(const char *name)