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Subject[PATCH v4 06/22] nvmem: use kref
Date
From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

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>
---
drivers/nvmem/core.c | 44 ++++++++++++++++++++++----------------------
1 file changed, 22 insertions(+), 22 deletions(-)

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index ffed8fa16936..552ffedce38e 100644
--- 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 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
}
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)
--
2.18.0
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