For various reasons, the available properties of the platform device
node in the device tree node should be referred to by the property name.
Passing type = VFIO_DEVTREE_PROP_NAMES to VFIO_DEVICE_GET_DEVTREE_INFO,
returns a list of strings with the available properties that the VFIO
user can access.

Signed-off-by: Antonios Motakis <a.mota...@virtualopensystems.com>
---
 drivers/vfio/platform/devtree.c | 68 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 67 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/platform/devtree.c b/drivers/vfio/platform/devtree.c
index 91cab88..b8fd4138 100644
--- a/drivers/vfio/platform/devtree.c
+++ b/drivers/vfio/platform/devtree.c
@@ -20,8 +20,74 @@ bool vfio_platform_has_devtree(struct vfio_platform_device 
*vdev)
        return !!vdev->of_node;
 }
 
+static int devtree_get_prop_names(struct device_node *np, void __user *datap,
+                                 unsigned long datasz, int *lenp)
+{
+       struct property *prop;
+       int len = 0, sz;
+       int ret = 0;
+
+       for_each_property_of_node(np, prop) {
+               sz = strlen(prop->name) + 1;
+
+               if (datasz < sz) {
+                       ret = -EAGAIN;
+                       break;
+               }
+
+               if (copy_to_user(datap, prop->name, sz))
+                       return -EFAULT;
+
+               datap += sz;
+               datasz -= sz;
+               len += sz;
+       }
+
+       /* if overflow occurs, calculate remaining length */
+       while (prop) {
+               len += strlen(prop->name) + 1;
+               prop = prop->next;
+       }
+
+       /* we expose the full_name in addition to the usual properties */
+       len += sz = strlen("full_name") + 1;
+       if (datasz < sz) {
+               ret = -EAGAIN;
+       } else if (copy_to_user(datap, "full_name", sz))
+               return -EFAULT;
+
+       *lenp = len;
+
+       return ret;
+}
+
 long vfio_platform_devtree_ioctl(struct vfio_platform_device *vdev,
                                 unsigned long arg)
 {
-       return -EINVAL; /* not implemented yet */
+       struct vfio_devtree_info info;
+       unsigned long minsz = offsetofend(struct vfio_devtree_info, length);
+       void __user *datap = (void __user *) arg + minsz;
+       unsigned long int datasz;
+       int ret = -EINVAL;
+
+       if (!vfio_platform_has_devtree(vdev))
+               return -EINVAL;
+
+       if (copy_from_user(&info, (void __user *)arg, minsz))
+               return -EFAULT;
+
+       if (info.argsz < minsz)
+               return -EINVAL;
+
+       datasz = info.argsz - minsz;
+
+       if (info.type == VFIO_DEVTREE_PROP_NAMES) {
+               ret = devtree_get_prop_names(vdev->of_node, datap, datasz,
+                                                               &info.length);
+       }
+
+       if (copy_to_user((void __user *)arg, &info, minsz))
+               ret = -EFAULT;
+
+       return ret;
 }
-- 
1.8.3.2

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