VFIO: platform: populate the reset function on probe

The reset function lookup happens on vfio-platform probe. The reset
module load is requested  and a reference to the function symbol is
hold. The reference is released on vfio-platform remove.
Signed-off-by: Eric Auger <eric.auger@linaro.org>
Acked-by: Baptiste Reynal <b.reynal@virtualopensystems.com>
Tested-by: Baptiste Reynal <b.reynal@virtualopensystems.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/platform/vfio_platform_common.c

@@ -28,6 +28,36 @@ static DEFINE_MUTEX(driver_lock);
 static const struct vfio_platform_reset_combo reset_lookup_table[] = {
 };
 
+static void vfio_platform_get_reset(struct vfio_platform_device *vdev,
+				    struct device *dev)
+{
+	const char *compat;
+	int (*reset)(struct vfio_platform_device *);
+	int ret, i;
+
+	ret = device_property_read_string(dev, "compatible", &compat);
+	if (ret)
+		return;
+
+	for (i = 0 ; i < ARRAY_SIZE(reset_lookup_table); i++) {
+		if (!strcmp(reset_lookup_table[i].compat, compat)) {
+			request_module(reset_lookup_table[i].module_name);
+			reset = __symbol_get(
+				reset_lookup_table[i].reset_function_name);
+			if (reset) {
+				vdev->reset = reset;
+				return;
+			}
+		}
+	}
+}
+
+static void vfio_platform_put_reset(struct vfio_platform_device *vdev)
+{
+	if (vdev->reset)
+		symbol_put_addr(vdev->reset);
+}
+
 static int vfio_platform_regions_init(struct vfio_platform_device *vdev)
 {
 	int cnt = 0, i;
@@ -516,6 +546,8 @@ int vfio_platform_probe_common(struct vfio_platform_device *vdev,
 		return ret;
 	}
 
+	vfio_platform_get_reset(vdev, dev);
+
 	mutex_init(&vdev->igate);
 
 	return 0;
@@ -527,8 +559,11 @@ struct vfio_platform_device *vfio_platform_remove_common(struct device *dev)
 	struct vfio_platform_device *vdev;
 
 	vdev = vfio_del_group_dev(dev);
-	if (vdev)
+
+	if (vdev) {
+		vfio_platform_put_reset(vdev);
 		iommu_group_put(dev->iommu_group);
+	}
 
 	return vdev;
 }