MFC 305034: Implement 'devctl clear driver' to undo a previous 'set driver'.

Add a new 'clear driver' command for devctl along with the accompanying
ioctl and devctl_clear_driver() library routine to reset a device to
use a wildcard devclass instead of a fixed devclass.  This can be used
to undo a previous 'set driver' command.  After the device's name has
been reset to permit wildcard names, it is reprobed so that it can
attach to newly-available (to it) device drivers.

Sponsored by:	Chelsio Communications

1 files changed, 20 insertions, 0 deletions

diff --git a/sys/kern/subr_bus.c b/sys/kern/subr_bus.c
index aba4364..6ccda55 100644
--- a/sys/kern/subr_bus.c
+++ b/sys/kern/subr_bus.c
@@ -5069,6 +5069,7 @@ devctl2_ioctl(struct cdev *cdev, u_long cmd, caddr_t data, int fflag,
 	case DEV_ENABLE:
 	case DEV_DISABLE:
 	case DEV_SET_DRIVER:
+	case DEV_CLEAR_DRIVER:
 		error = priv_check(td, PRIV_DRIVER);
 		if (error == 0)
 			error = find_device(req, &dev);
@@ -5210,6 +5211,25 @@ devctl2_ioctl(struct cdev *cdev, u_long cmd, caddr_t data, int fflag,
 		error = device_probe_and_attach(dev);
 		break;
 	}
+	case DEV_CLEAR_DRIVER:
+		if (!(dev->flags & DF_FIXEDCLASS)) {
+			error = 0;
+			break;
+		}
+		if (device_is_attached(dev)) {
+			if (req->dr_flags & DEVF_CLEAR_DRIVER_DETACH)
+				error = device_detach(dev);
+			else
+				error = EBUSY;
+			if (error)
+				break;
+		}
+
+		dev->flags &= ~DF_FIXEDCLASS;
+		dev->flags |= DF_WILDCARD;
+		devclass_delete_device(dev->devclass, dev);
+		error = device_probe_and_attach(dev);
+		break;
 	}
 	mtx_unlock(&Giant);
 	return (error);