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    Subject[PATCH v3 06/21] 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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