[RFC PATCH 1/7] vfio: Include optional device match in vfio_device_ops callbacks

[Alex Williamson <alex.williamson@xxxxxxxxxx>]

Allow bus drivers to provide their own callback to match a device to
the user provided string.

Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
---
 drivers/vfio/vfio.c  |   19 +++++++++++++++----
 include/linux/vfio.h |    3 +++
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 388597930b64..dda1726adda8 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -875,11 +875,22 @@ EXPORT_SYMBOL_GPL(vfio_device_get_from_dev);
 static struct vfio_device *vfio_device_get_from_name(struct vfio_group *group,
 						     char *buf)
 {
-	struct vfio_device *it, *device = NULL;
+	struct vfio_device *it, *device = ERR_PTR(-ENODEV);
 
 	mutex_lock(&group->device_lock);
 	list_for_each_entry(it, &group->device_list, group_next) {
-		if (!strcmp(dev_name(it->dev), buf)) {
+		int ret;
+
+		if (it->ops->match) {
+			ret = it->ops->match(it->device_data, buf);
+			if (ret < 0 && ret != -ENODEV) {
+				device = ERR_PTR(ret);
+				break;
+			}
+		} else
+			ret = strcmp(dev_name(it->dev), buf);
+
+		if (!ret) {
 			device = it;
 			vfio_device_get(device);
 			break;
@@ -1441,8 +1452,8 @@ static int vfio_group_get_device_fd(struct vfio_group *group, char *buf)
 		return -EPERM;
 
 	device = vfio_device_get_from_name(group, buf);
-	if (!device)
-		return -ENODEV;
+	if (IS_ERR(device))
+		return PTR_ERR(device);
 
 	ret = device->ops->open(device->device_data);
 	if (ret) {
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index e42a711a2800..755e0f0e2900 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -26,6 +26,8 @@
  *         operations documented below
  * @mmap: Perform mmap(2) on a region of the device file descriptor
  * @request: Request for the bus driver to release the device
+ * @match: Optional device name match callback (return: 0 for match, -ENODEV
+ *         (or >0) for no match and continue, other -errno: no match and stop)
  */
 struct vfio_device_ops {
 	char	*name;
@@ -39,6 +41,7 @@ struct vfio_device_ops {
 			 unsigned long arg);
 	int	(*mmap)(void *device_data, struct vm_area_struct *vma);
 	void	(*request)(void *device_data, unsigned int count);
+	int	(*match)(void *device_data, char *buf);
 };
 
 extern struct iommu_group *vfio_iommu_group_get(struct device *dev);