VFIO: Wrapper for getting reference to vfio_device

- Added vfio_device_get_from_dev() as wrapper to get
  reference to vfio_device from struct device.

- Added vfio_device_data() as a wrapper to get device_data from
  vfio_device.

Signed-off-by: Vijay Mohan Pandarathil <vijaymohan.pandarathil@hp.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

1 files changed, 29 insertions, 1 deletions

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index fcc12f3e60a3..21eddd9e0f26 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -392,12 +392,13 @@ static void vfio_device_release(struct kref *kref)
 }
 
 /* Device reference always implies a group reference */
-static void vfio_device_put(struct vfio_device *device)
+void vfio_device_put(struct vfio_device *device)
 {
         struct vfio_group *group = device->group;
         kref_put_mutex(&device->kref, vfio_device_release, &group->device_lock);
         vfio_group_put(group);
 }
+EXPORT_SYMBOL_GPL(vfio_device_put);
 
 static void vfio_device_get(struct vfio_device *device)
 {
@@ -627,6 +628,33 @@ int vfio_add_group_dev(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(vfio_add_group_dev);
 
+/**
+ * Get a reference to the vfio_device for a device that is known to
+ * be bound to a vfio driver.  The driver implicitly holds a
+ * vfio_device reference between vfio_add_group_dev and
+ * vfio_del_group_dev.  We can therefore use drvdata to increment
+ * that reference from the struct device.  This additional
+ * reference must be released by calling vfio_device_put.
+ */
+struct vfio_device *vfio_device_get_from_dev(struct device *dev)
+{
+        struct vfio_device *device = dev_get_drvdata(dev);
+
+        vfio_device_get(device);
+
+        return device;
+}
+EXPORT_SYMBOL_GPL(vfio_device_get_from_dev);
+
+/*
+ * Caller must hold a reference to the vfio_device
+ */
+void *vfio_device_data(struct vfio_device *device)
+{
+        return device->device_data;
+}
+EXPORT_SYMBOL_GPL(vfio_device_data);
+
 /* Given a referenced group, check if it contains the device */
 static bool vfio_dev_present(struct vfio_group *group, struct device *dev)
 {