Similar to 189574, properly handle subclasses of bus drivers when deleting

a driver during kldunload.  Specifically, recursively walk the tree of
subclasses of a given driver attachment's bus device class detaching all
instances of that driver for each class and its subclasses.

Reported by:	bschmidt
Reviewed by:	imp
MFC after:	1 week

1 files changed, 81 insertions, 30 deletions

diff --git a/sys/kern/subr_bus.c b/sys/kern/subr_bus.c
index 30d374a..f6b1ecc 100644
--- a/sys/kern/subr_bus.c
+++ b/sys/kern/subr_bus.c
@@ -987,10 +987,12 @@ devclass_find(const char *classname)
  * is called by devclass_add_driver to accomplish the recursive
  * notification of all the children classes of dc, as well as dc.
  * Each layer will have BUS_DRIVER_ADDED() called for all instances of
- * the devclass.  We do a full search here of the devclass list at
- * each iteration level to save storing children-lists in the devclass
- * structure.  If we ever move beyond a few dozen devices doing this,
- * we may need to reevaluate...
+ * the devclass.
+ *
+ * We do a full search here of the devclass list at each iteration
+ * level to save storing children-lists in the devclass structure.  If
+ * we ever move beyond a few dozen devices doing this, we may need to
+ * reevaluate...
  *
  * @param dc		the devclass to edit
  * @param driver	the driver that was just added
@@ -1085,6 +1087,78 @@ devclass_add_driver(devclass_t dc, driver_t *driver, int pass, devclass_t *dcp)
 }
 
 /**
+ * @brief Register that a device driver has been deleted from a devclass
+ *
+ * Register that a device driver has been removed from a devclass.
+ * This is called by devclass_delete_driver to accomplish the
+ * recursive notification of all the children classes of busclass, as
+ * well as busclass.  Each layer will attempt to detach the driver
+ * from any devices that are children of the bus's devclass.  The function
+ * will return an error if a device fails to detach.
+ * 
+ * We do a full search here of the devclass list at each iteration
+ * level to save storing children-lists in the devclass structure.  If
+ * we ever move beyond a few dozen devices doing this, we may need to
+ * reevaluate...
+ *
+ * @param busclass	the devclass of the parent bus
+ * @param dc		the devclass of the driver being deleted
+ * @param driver	the driver being deleted
+ */
+static int
+devclass_driver_deleted(devclass_t busclass, devclass_t dc, driver_t *driver)
+{
+	devclass_t parent;
+	device_t dev;
+	int error, i;
+
+	/*
+	 * Disassociate from any devices.  We iterate through all the
+	 * devices in the devclass of the driver and detach any which are
+	 * using the driver and which have a parent in the devclass which
+	 * we are deleting from.
+	 *
+	 * Note that since a driver can be in multiple devclasses, we
+	 * should not detach devices which are not children of devices in
+	 * the affected devclass.
+	 */
+	for (i = 0; i < dc->maxunit; i++) {
+		if (dc->devices[i]) {
+			dev = dc->devices[i];
+			if (dev->driver == driver && dev->parent &&
+			    dev->parent->devclass == busclass) {
+				if ((error = device_detach(dev)) != 0)
+					return (error);
+				device_set_driver(dev, NULL);
+				BUS_PROBE_NOMATCH(dev->parent, dev);
+				devnomatch(dev);
+				dev->flags |= DF_DONENOMATCH;
+			}
+		}
+	}
+
+	/*
+	 * Walk through the children classes.  Since we only keep a
+	 * single parent pointer around, we walk the entire list of
+	 * devclasses looking for children.  We set the
+	 * DC_HAS_CHILDREN flag when a child devclass is created on
+	 * the parent, so we only walk the list for those devclasses
+	 * that have children.
+	 */
+	if (!(busclass->flags & DC_HAS_CHILDREN))
+		return (0);
+	parent = busclass;
+	TAILQ_FOREACH(busclass, &devclasses, link) {
+		if (busclass->parent == parent) {
+			error = devclass_driver_deleted(busclass, dc, driver);
+			if (error)
+				return (error);
+		}
+	}
+	return (0);
+}
+
+/**
  * @brief Delete a device driver from a device class
  *
  * Delete a device driver from a devclass. This is normally called
@@ -1103,8 +1177,6 @@ devclass_delete_driver(devclass_t busclass, driver_t *driver)
 {
 	devclass_t dc = devclass_find(driver->name);
 	driverlink_t dl;
-	device_t dev;
-	int i;
 	int error;
 
 	PDEBUG(("%s from devclass %s", driver->name, DEVCLANAME(busclass)));
@@ -1126,30 +1198,9 @@ devclass_delete_driver(devclass_t busclass, driver_t *driver)
 		return (ENOENT);
 	}
 
-	/*
-	 * Disassociate from any devices.  We iterate through all the
-	 * devices in the devclass of the driver and detach any which are
-	 * using the driver and which have a parent in the devclass which
-	 * we are deleting from.
-	 *
-	 * Note that since a driver can be in multiple devclasses, we
-	 * should not detach devices which are not children of devices in
-	 * the affected devclass.
-	 */
-	for (i = 0; i < dc->maxunit; i++) {
-		if (dc->devices[i]) {
-			dev = dc->devices[i];
-			if (dev->driver == driver && dev->parent &&
-			    dev->parent->devclass == busclass) {
-				if ((error = device_detach(dev)) != 0)
-					return (error);
-				device_set_driver(dev, NULL);
-				BUS_PROBE_NOMATCH(dev->parent, dev);
-				devnomatch(dev);
-				dev->flags |= DF_DONENOMATCH;
-			}
-		}
-	}
+	error = devclass_driver_deleted(busclass, dc, driver);
+	if (error != 0)
+		return (error);
 
 	TAILQ_REMOVE(&busclass->drivers, dl, link);
 	free(dl, M_BUS);