virtio: console: Let host know of port or device add failures

The host may want to know and let management apps notify of port or
device add failures. Send a control message saying the device or port is
not ready in this case.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

drivers/char/virtio_console.c

@@ -1210,6 +1210,8 @@ free_cdev:
 free_port:
 	kfree(port);
 fail:
+	/* The host might want to notify management sw about port add failure */
+	send_control_msg(port, VIRTIO_CONSOLE_PORT_READY, 0);
 	return err;
 }
 
@@ -1488,6 +1490,9 @@ free_chrdev:
 free:
 	kfree(portdev);
 fail:
+	/* The host might want to notify mgmt sw about device add failure */
+	__send_control_msg(portdev, VIRTIO_CONSOLE_BAD_ID,
+			   VIRTIO_CONSOLE_DEVICE_READY, 0);
 	return err;
 }
 

include/linux/virtio_console.h

@@ -14,6 +14,8 @@
 #define VIRTIO_CONSOLE_F_SIZE	0	/* Does host provide console size? */
 #define VIRTIO_CONSOLE_F_MULTIPORT 1	/* Does host provide multiple ports? */
 
+#define VIRTIO_CONSOLE_BAD_ID		(~(u32)0)
+
 struct virtio_console_config {
 	/* colums of the screens */
 	__u16 cols;
@@ -42,6 +44,7 @@ struct virtio_console_control {
 #define VIRTIO_CONSOLE_PORT_OPEN	3
 #define VIRTIO_CONSOLE_PORT_NAME	4
 #define VIRTIO_CONSOLE_PORT_REMOVE	5
+#define VIRTIO_CONSOLE_DEVICE_READY	6
 
 #ifdef __KERNEL__
 int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int));