Implement 'devctl clear driver' to undo a previous 'devctl 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.

MFC after:	1 month
Sponsored by:	Chelsio Communications

lib/libdevctl/devctl.3

@@ -25,12 +25,13 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd April 27, 2016
+.Dd August 29, 2016
 .Dt DEVCTL 3
 .Os
 .Sh NAME
 .Nm devctl ,
 .Nm devctl_attach ,
+.Nm devctl_clear_driver ,
 .Nm devctl_delete ,
 .Nm devctl_detach ,
 .Nm devctl_disable ,
@@ -47,6 +48,8 @@
 .Ft int
 .Fn devctl_attach "const char *device"
 .Ft int
+.Fn devctl_clear_driver "const char *device" "bool force"
+.Ft int
 .Fn devctl_delete "const char *device" "bool force"
 .Ft int
 .Fn devctl_detach "const char *device" "bool force"
@@ -166,12 +169,30 @@ the device will be detached from its current device driver before it is
 attached to the new device driver.
 .Pp
 The
+.Fn devctl_clear_driver
+function resets a device so that it can be attached to any valid device
+driver rather than only drivers with a previously specified name.
+This function is used to undo a previous call to
+.Fn devctl_set_driver .
+If the device is already attached and
+.Fa force
+is false,
+the request will fail.
+If the device is already attached and
+.Fa force
+is true,
+the device will be detached from its current device driver.
+After the device's name is reset,
+it is reprobed and attached to a suitable device driver if one is found.
+.Pp
+The
 .Fn devctl_rescan
 function rescans a bus device checking for devices that have been added or
 removed.
 .Sh RETURN VALUES
-.Rv -std devctl_attach devctl_delete devctl_detach devctl_disable \
-devctl_enable devctl_suspend devctl_rescan devctl_resume devctl_set_driver
+.Rv -std devctl_attach devctl_clear_driver devctl_delete devctl_detach \
+devctl_disable devctl_enable devctl_suspend devctl_rescan devctl_resume \
+devctl_set_driver
 .Sh ERRORS
 In addition to specific errors noted below,
 all of the
@@ -302,6 +323,24 @@ The new device driver failed to attach.
 .El
 .Pp
 The
+.Fn devctl_clear_driver
+function may fail if:
+.Bl -tag -width Er
+.It Bq Er EBUSY
+The device is currently attached to a device driver and
+.Fa force
+is false.
+.It Bq Er EBUSY
+The current device driver for
+.Fa device
+is busy and cannot detach at this time.
+.It Bq Er EINVAL
+The device is not configured for a specific device driver name.
+.It Bq Er ENXIO
+The device driver chosen after reprobing failed to attach.
+.El
+.Pp
+The
 .Fn devctl_rescan
 function may fail if:
 .Bl -tag -width Er

lib/libdevctl/devctl.c

@@ -123,6 +123,14 @@ devctl_set_driver(const char *device, const char *driver, bool force)
 	return (devctl_request(DEV_SET_DRIVER, &req));
 }
 
+int
+devctl_clear_driver(const char *device, bool force)
+{
+
+	return (devctl_simple_request(DEV_CLEAR_DRIVER, device, force ?
+	    DEVF_CLEAR_DRIVER_DETACH : 0));
+}
+
 int
 devctl_rescan(const char *device)
 {

lib/libdevctl/devctl.h

@@ -38,6 +38,7 @@ int	devctl_disable(const char *device, bool force_detach);
 int	devctl_suspend(const char *device);
 int	devctl_resume(const char *device);
 int	devctl_set_driver(const char *device, const char *driver, bool force);
+int	devctl_clear_driver(const char *device, bool force);
 int	devctl_rescan(const char *device);
 int	devctl_delete(const char *device, bool force);
 

sys/kern/subr_bus.c

@@ -5349,6 +5349,7 @@ devctl2_ioctl(struct cdev *cdev, u_long cmd, caddr_t data, int fflag,
 	case DEV_SUSPEND:
 	case DEV_RESUME:
 	case DEV_SET_DRIVER:
+	case DEV_CLEAR_DRIVER:
 	case DEV_RESCAN:
 	case DEV_DELETE:
 		error = priv_check(td, PRIV_DRIVER);
@@ -5514,6 +5515,25 @@ 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;
 	case DEV_RESCAN:
 		if (!device_is_attached(dev)) {
 			error = ENXIO;

sys/sys/bus.h

@@ -117,6 +117,7 @@ struct devreq {
 #define	DEV_SUSPEND	_IOW('D', 5, struct devreq)
 #define	DEV_RESUME	_IOW('D', 6, struct devreq)
 #define	DEV_SET_DRIVER	_IOW('D', 7, struct devreq)
+#define	DEV_CLEAR_DRIVER _IOW('D', 8, struct devreq)
 #define	DEV_RESCAN	_IOW('D', 9, struct devreq)
 #define	DEV_DELETE	_IOW('D', 10, struct devreq)
 
@@ -126,6 +127,9 @@ struct devreq {
 /* Flags for DEV_SET_DRIVER. */
 #define	DEVF_SET_DRIVER_DETACH	0x0000001	/* Detach existing driver. */
 
+/* Flags for DEV_CLEAR_DRIVER. */
+#define	DEVF_CLEAR_DRIVER_DETACH 0x0000001	/* Detach existing driver. */
+
 /* Flags for DEV_DELETE. */
 #define	DEVF_FORCE_DELETE	0x0000001
 

usr.sbin/devctl/devctl.8

@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd April 27, 2016
+.Dd August 29, 2016
 .Dt DEVCTL 8
 .Os
 .Sh NAME
@@ -36,6 +36,10 @@
 .Cm attach
 .Ar device
 .Nm
+.Cm clear driver
+.Op Fl f
+.Ar device
+.Nm
 .Cm detach
 .Op Fl f
 .Ar device
@@ -133,6 +137,21 @@ If the device is already attached to a device driver and the
 .Fl f
 flag is not specified,
 the device will not be changed.
+.It Xo Cm clear driver
+.Op Fl f
+.Ar device
+.Xc
+Clear a previously-forced driver name so that the device is able to use any
+valid device driver.
+After the previous name has been cleared,
+the device is reprobed so that other device drivers may attach to it.
+This can be used to undo an earlier
+.Cm set driver
+command.
+If the device is currently attached to a device driver and the
+.Fl f
+flag is not specified,
+the device will not be changed.
 .It Cm rescan Ar device
 Rescan a bus device checking for devices that have been added or
 removed.

usr.sbin/devctl/devctl.c

@@ -65,12 +65,13 @@ static int	devctl_table_handler(struct devctl_command **start,
 
 SET_DECLARE(DEVCTL_DATASET(top), struct devctl_command);
 
+DEVCTL_TABLE(top, clear);
 DEVCTL_TABLE(top, set);
 
 static void
 usage(void)
 {
-	fprintf(stderr, "%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n",
+	fprintf(stderr, "%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n%s\n",
 	    "usage: devctl attach device",
 	    "       devctl detach [-f] device",
 	    "       devctl disable [-f] device",
@@ -78,6 +79,7 @@ usage(void)
 	    "       devctl suspend device",
 	    "       devctl resume device",
 	    "       devctl set driver [-f] device driver",
+	    "       devctl clear driver [-f] device",
 	    "       devctl rescan device",
 	    "       devctl delete [-f] device");
 	exit(1);
@@ -261,6 +263,40 @@ set_driver(int ac, char **av)
 }
 DEVCTL_COMMAND(set, driver, set_driver);
 
+static void
+clear_driver_usage(void)
+{
+
+	fprintf(stderr, "usage: devctl clear driver [-f] device\n");
+	exit(1);
+}
+
+static int
+clear_driver(int ac, char **av)
+{
+	bool force;
+	int ch;
+
+	force = false;
+	while ((ch = getopt(ac, av, "f")) != -1)
+		switch (ch) {
+		case 'f':
+			force = true;
+			break;
+		default:
+			clear_driver_usage();
+		}
+	ac -= optind;
+	av += optind;
+
+	if (ac != 1)
+		clear_driver_usage();
+	if (devctl_clear_driver(av[0], force) < 0)
+		err(1, "Failed to clear %s driver", av[0]);
+	return (0);
+}
+DEVCTL_COMMAND(clear, driver, clear_driver);
+
 static int
 rescan(int ac, char **av)
 {