[PATCH v2 1/7] staging: unisys: visorinput: use kref ref-counting for device data struct

[Benjamin Romer]

From: Tim Sell <timothy.s...@unisys.com>

This is NOT technically required for the code as it stands now, but will
be needed for subsequent patches.

Signed-off-by: Tim Sell <timothy.s...@unisys.com>
Signed-off-by: Benjamin Romer <benjamin.ro...@unisys.com>

---
v2: resources are released in the reverse order they were acquired, as per
    Dan Carpenter's comment.
---
 drivers/staging/unisys/visorinput/visorinput.c | 45 ++++++++++++++++++++------
 1 file changed, 35 insertions(+), 10 deletions(-)

diff --git a/drivers/staging/unisys/visorinput/visorinput.c 
b/drivers/staging/unisys/visorinput/visorinput.c
index 5c16f66..238a132 100644
--- a/drivers/staging/unisys/visorinput/visorinput.c
+++ b/drivers/staging/unisys/visorinput/visorinput.c
@@ -62,6 +62,7 @@ enum visorinput_device_type {
  * dev_get_drvdata() / dev_set_drvdata() for each struct device.
  */
 struct visorinput_devdata {
+       struct kref kref;
        struct visor_device *dev;
        struct rw_semaphore lock_visor_dev; /* lock for dev */
        struct input_dev *visorinput_dev;
@@ -346,6 +347,35 @@ register_client_mouse(void *devdata /* opaque on purpose 
*/)
        return visorinput_dev;
 }
 
+static void
+unregister_client_input(struct input_dev *visorinput_dev)
+{
+       if (visorinput_dev)
+               input_unregister_device(visorinput_dev);
+}
+
+static void devdata_release(struct kref *kref)
+{
+       struct visorinput_devdata *devdata =
+               container_of(kref, struct visorinput_devdata, kref);
+       unregister_client_input(devdata->visorinput_dev);
+       kfree(devdata);
+}
+
+static struct visorinput_devdata *
+devdata_get(struct visorinput_devdata *devdata)
+{
+       if (devdata)
+               kref_get(&devdata->kref);
+       return devdata;
+}
+
+static void devdata_put(struct visorinput_devdata *devdata)
+{
+       if (devdata)
+               kref_put(&devdata->kref, devdata_release);
+}
+
 static struct visorinput_devdata *
 devdata_create(struct visor_device *dev, enum visorinput_device_type devtype)
 {
@@ -385,6 +415,7 @@ devdata_create(struct visor_device *dev, enum 
visorinput_device_type devtype)
        }
 
        init_rwsem(&devdata->lock_visor_dev);
+       kref_init(&devdata->kref);
 
        return devdata;
 
@@ -415,13 +446,6 @@ visorinput_probe(struct visor_device *dev)
 }
 
 static void
-unregister_client_input(struct input_dev *visorinput_dev)
-{
-       if (visorinput_dev)
-               input_unregister_device(visorinput_dev);
-}
-
-static void
 visorinput_remove(struct visor_device *dev)
 {
        struct visorinput_devdata *devdata = dev_get_drvdata(&dev->device);
@@ -438,9 +462,8 @@ visorinput_remove(struct visor_device *dev)
 
        down_write(&devdata->lock_visor_dev);
        dev_set_drvdata(&dev->device, NULL);
-       unregister_client_input(devdata->visorinput_dev);
        up_write(&devdata->lock_visor_dev);
-       kfree(devdata);
+       devdata_put(devdata);
 }
 
 /*
@@ -526,7 +549,8 @@ visorinput_channel_interrupt(struct visor_device *dev)
        int xmotion, ymotion, zmotion, button;
        int i;
 
-       struct visorinput_devdata *devdata = dev_get_drvdata(&dev->device);
+       struct visorinput_devdata *devdata =
+               devdata_get(dev_get_drvdata(&dev->device));
 
        if (!devdata)
                return;
@@ -617,6 +641,7 @@ visorinput_channel_interrupt(struct visor_device *dev)
        }
 out_locked:
        up_write(&devdata->lock_visor_dev);
+       devdata_put(devdata);
 }
 
 static int
-- 
2.5.0

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