linux-kernel - [PATCH v2 03/16] nvmem: use kref

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Message-Id: <20180907100750.14564-4-brgl@bgdev.pl>
Date:   Fri,  7 Sep 2018 12:07:37 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        "David S . Miller" <davem@...emloft.net>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>, Sekhar Nori <nsekhar@...com>,
        Kevin Hilman <khilman@...nel.org>,
        David Lechner <david@...hnology.com>,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        Andrew Lunn <andrew@...n.ch>, Alban Bedel <albeu@...e.fr>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Chen-Yu Tsai <wens@...e.org>
Cc:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: [PATCH v2 03/16] nvmem: use kref

From: Bartosz Golaszewski <bgolaszewski@...libre.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@...libre.com>
---
 drivers/nvmem/core.c | 45 +++++++++++++++++++++-----------------------
 1 file changed, 21 insertions(+), 24 deletions(-)

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index 86af62e2df47..2335b72d4b3e 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -32,7 +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;
@@ -368,6 +368,8 @@ 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)
@@ -430,6 +432,20 @@ 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
  *
@@ -439,19 +455,7 @@ 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;
 }
@@ -517,7 +521,6 @@ int devm_nvmem_unregister(struct device *dev, struct nvmem_device *nvmem)
 }
 EXPORT_SYMBOL(devm_nvmem_unregister);
 
-
 static struct nvmem_device *__nvmem_device_get(struct device_node *np)
 {
 	struct nvmem_device *nvmem = NULL;
@@ -533,30 +536,24 @@ static struct nvmem_device *__nvmem_device_get(struct device_node *np)
 		return ERR_PTR(-EPROBE_DEFER);
 	}
 
-	nvmem->users++;
 	mutex_unlock(&nvmem_mutex);
 
 	if (!try_module_get(nvmem->owner)) {
 		dev_err(&nvmem->dev,
 			"could not increase module refcount for cell %s\n",
 			nvmem->name);
-
-		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