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

2 files changed, 57 insertions, 2 deletions

diff --git a/usr.sbin/devctl/devctl.8 b/usr.sbin/devctl/devctl.8
index ec8abaff233a..67b870960fe4 100644
--- a/usr.sbin/devctl/devctl.8
+++ b/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.
diff --git a/usr.sbin/devctl/devctl.c b/usr.sbin/devctl/devctl.c
index 824b9075c04e..6b266f42fe40 100644
--- a/usr.sbin/devctl/devctl.c
+++ b/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)
 {