[PATCH v5 01/11] firmware: raspberrypi: Keep count of all consumers

[Nicolas Saenz Julienne]

When unbinding the firmware device we need to make sure it has no
consumers left. Otherwise we'd leave them with a firmware handle
pointing at freed memory.

Keep a reference count of all consumers and introduce rpi_firmware_put()
which will permit automatically decrease the reference count upon
unbinding consumer drivers.

Suggested-by: Uwe Kleine-König <u.kleine-koe...@pengutronix.de>
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulie...@suse.de>
---

Changes since v3:
- Use kref instead of waiting on refcount

 drivers/firmware/raspberrypi.c             | 37 +++++++++++++++++++---
 include/soc/bcm2835/raspberrypi-firmware.h |  2 ++
 2 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/drivers/firmware/raspberrypi.c b/drivers/firmware/raspberrypi.c
index 30259dc9b805..ed793aef7851 100644
--- a/drivers/firmware/raspberrypi.c
+++ b/drivers/firmware/raspberrypi.c
@@ -7,6 +7,7 @@
  */
 
 #include <linux/dma-mapping.h>
+#include <linux/kref.h>
 #include <linux/mailbox_client.h>
 #include <linux/module.h>
 #include <linux/of_platform.h>
@@ -27,6 +28,8 @@ struct rpi_firmware {
        struct mbox_chan *chan; /* The property channel. */
        struct completion c;
        u32 enabled;
+
+       struct kref consumers;
 };
 
 static DEFINE_MUTEX(transaction_lock);
@@ -225,12 +228,27 @@ static void rpi_register_clk_driver(struct device *dev)
                                                -1, NULL, 0);
 }
 
+static void rpi_firmware_delete(struct kref *kref)
+{
+       struct rpi_firmware *fw = container_of(kref, struct rpi_firmware,
+                                              consumers);
+
+       mbox_free_channel(fw->chan);
+       kfree(fw);
+}
+
+void rpi_firmware_put(struct rpi_firmware *fw)
+{
+       kref_put(&fw->consumers, rpi_firmware_delete);
+}
+EXPORT_SYMBOL_GPL(rpi_firmware_put);
+
 static int rpi_firmware_probe(struct platform_device *pdev)
 {
        struct device *dev = &pdev->dev;
        struct rpi_firmware *fw;
 
-       fw = devm_kzalloc(dev, sizeof(*fw), GFP_KERNEL);
+       fw = kzalloc(sizeof(*fw), GFP_KERNEL);
        if (!fw)
                return -ENOMEM;
 
@@ -247,6 +265,7 @@ static int rpi_firmware_probe(struct platform_device *pdev)
        }
 
        init_completion(&fw->c);
+       kref_init(&fw->consumers);
 
        platform_set_drvdata(pdev, fw);
 
@@ -275,25 +294,35 @@ static int rpi_firmware_remove(struct platform_device 
*pdev)
        rpi_hwmon = NULL;
        platform_device_unregister(rpi_clk);
        rpi_clk = NULL;
-       mbox_free_channel(fw->chan);
+
+       rpi_firmware_put(fw);
 
        return 0;
 }
 
 /**
- * rpi_firmware_get - Get pointer to rpi_firmware structure.
  * @firmware_node:    Pointer to the firmware Device Tree node.
  *
+ * The reference to rpi_firmware has to be released with rpi_firmware_put().
+ *
  * Returns NULL is the firmware device is not ready.
  */
 struct rpi_firmware *rpi_firmware_get(struct device_node *firmware_node)
 {
        struct platform_device *pdev = of_find_device_by_node(firmware_node);
+       struct rpi_firmware *fw;
 
        if (!pdev)
                return NULL;
 
-       return platform_get_drvdata(pdev);
+       fw = platform_get_drvdata(pdev);
+       if (!fw)
+               return NULL;
+
+       if (!kref_get_unless_zero(&fw->consumers))
+               return NULL;
+
+       return fw;
 }
 EXPORT_SYMBOL_GPL(rpi_firmware_get);
 
diff --git a/include/soc/bcm2835/raspberrypi-firmware.h 
b/include/soc/bcm2835/raspberrypi-firmware.h
index cc9cdbc66403..fdfef7fe40df 100644
--- a/include/soc/bcm2835/raspberrypi-firmware.h
+++ b/include/soc/bcm2835/raspberrypi-firmware.h
@@ -140,6 +140,7 @@ int rpi_firmware_property(struct rpi_firmware *fw,
                          u32 tag, void *data, size_t len);
 int rpi_firmware_property_list(struct rpi_firmware *fw,
                               void *data, size_t tag_size);
+void rpi_firmware_put(struct rpi_firmware *fw);
 struct rpi_firmware *rpi_firmware_get(struct device_node *firmware_node);
 #else
 static inline int rpi_firmware_property(struct rpi_firmware *fw, u32 tag,
@@ -154,6 +155,7 @@ static inline int rpi_firmware_property_list(struct 
rpi_firmware *fw,
        return -ENOSYS;
 }
 
+static inline void rpi_firmware_put(struct rpi_firmware *fw) { }
 static inline struct rpi_firmware *rpi_firmware_get(struct device_node 
*firmware_node)
 {
        return NULL;
-- 
2.29.2

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