s390/qeth: unbreak OSM and OSN support

commit b4d72c08b358 ("qeth: bridgeport support - basic control")
broke the support for OSM and OSN devices as follows:

As OSM and OSN are L2 only, qeth_core_probe_device() does an early
setup by loading the l2 discipline and calling qeth_l2_probe_device().
In this context, adding the l2-specific bridgeport sysfs attributes
via qeth_l2_create_device_attributes() hits a BUG_ON in fs/sysfs/group.c,
since the basic sysfs infrastructure for the device hasn't been
established yet.

Note that OSN actually has its own unique sysfs attributes
(qeth_osn_devtype), so the additional attributes shouldn't be created
at all.
For OSM, add a new qeth_l2_devtype that contains all the common
and l2-specific sysfs attributes.
When qeth_core_probe_device() does early setup for OSM or OSN, assign
the corresponding devtype so that the ccwgroup probe code creates the
full set of sysfs attributes.
This allows us to skip qeth_l2_create_device_attributes() in case
of an early setup.

Any device that can't do early setup will initially have only the
generic sysfs attributes, and when it's probed later
qeth_l2_probe_device() adds the l2-specific attributes.

If an early-setup device is removed (by calling ccwgroup_ungroup()),
device_unregister() will - using the devtype - delete the
l2-specific attributes before qeth_l2_remove_device() is called.
So make sure to not remove them twice.

What complicates the issue is that qeth_l2_probe_device() and
qeth_l2_remove_device() is also called on a device when its
layer2 attribute changes (ie. its layer mode is switched).
For early-setup devices this wouldn't work properly - we wouldn't
remove the l2-specific attributes when switching to L3.
But switching the layer mode doesn't actually make any sense;
we already decided that the device can only operate in L2!
So just refuse to switch the layer mode on such devices. Note that
OSN doesn't have a layer2 attribute, so we only need to special-case
OSM.

Based on an initial patch by Ursula Braun.

Fixes: b4d72c08b358 ("qeth: bridgeport support - basic control")
Signed-off-by: Julian Wiedmann <jwi@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/s390/net/qeth_core.h

@@ -701,6 +701,7 @@ enum qeth_discipline_id {
 };
 
 struct qeth_discipline {
+	const struct device_type *devtype;
 	void (*start_poll)(struct ccw_device *, int, unsigned long);
 	qdio_handler_t *input_handler;
 	qdio_handler_t *output_handler;
@@ -875,6 +876,9 @@ extern struct qeth_discipline qeth_l2_discipline;
 extern struct qeth_discipline qeth_l3_discipline;
 extern const struct attribute_group *qeth_generic_attr_groups[];
 extern const struct attribute_group *qeth_osn_attr_groups[];
+extern const struct attribute_group qeth_device_attr_group;
+extern const struct attribute_group qeth_device_blkt_group;
+extern const struct device_type qeth_generic_devtype;
 extern struct workqueue_struct *qeth_wq;
 
 int qeth_card_hw_is_reachable(struct qeth_card *);

drivers/s390/net/qeth_core_main.c

@@ -5530,10 +5530,12 @@ void qeth_core_free_discipline(struct qeth_card *card)
 	card->discipline = NULL;
 }
 
-static const struct device_type qeth_generic_devtype = {
+const struct device_type qeth_generic_devtype = {
 	.name = "qeth_generic",
 	.groups = qeth_generic_attr_groups,
 };
+EXPORT_SYMBOL_GPL(qeth_generic_devtype);
+
 static const struct device_type qeth_osn_devtype = {
 	.name = "qeth_osn",
 	.groups = qeth_osn_attr_groups,
@@ -5659,23 +5661,22 @@ static int qeth_core_probe_device(struct ccwgroup_device *gdev)
 		goto err_card;
 	}
 
-	if (card->info.type == QETH_CARD_TYPE_OSN)
-		gdev->dev.type = &qeth_osn_devtype;
-	else
-		gdev->dev.type = &qeth_generic_devtype;
-
 	switch (card->info.type) {
 	case QETH_CARD_TYPE_OSN:
 	case QETH_CARD_TYPE_OSM:
 		rc = qeth_core_load_discipline(card, QETH_DISCIPLINE_LAYER2);
 		if (rc)
 			goto err_card;
+
+		gdev->dev.type = (card->info.type != QETH_CARD_TYPE_OSN)
+					? card->discipline->devtype
+					: &qeth_osn_devtype;
 		rc = card->discipline->setup(card->gdev);
 		if (rc)
 			goto err_disc;
-	case QETH_CARD_TYPE_OSD:
-	case QETH_CARD_TYPE_OSX:
+		break;
 	default:
+		gdev->dev.type = &qeth_generic_devtype;
 		break;
 	}
 

drivers/s390/net/qeth_core_sys.c

@@ -413,12 +413,16 @@ static ssize_t qeth_dev_layer2_store(struct device *dev,
 
 	if (card->options.layer2 == newdis)
 		goto out;
-	else {
-		card->info.mac_bits  = 0;
-		if (card->discipline) {
-			card->discipline->remove(card->gdev);
-			qeth_core_free_discipline(card);
-		}
+	if (card->info.type == QETH_CARD_TYPE_OSM) {
+		/* fixed layer, can't switch */
+		rc = -EOPNOTSUPP;
+		goto out;
+	}
+
+	card->info.mac_bits = 0;
+	if (card->discipline) {
+		card->discipline->remove(card->gdev);
+		qeth_core_free_discipline(card);
 	}
 
 	rc = qeth_core_load_discipline(card, newdis);
@@ -705,10 +709,11 @@ static struct attribute *qeth_blkt_device_attrs[] = {
 	&dev_attr_inter_jumbo.attr,
 	NULL,
 };
-static struct attribute_group qeth_device_blkt_group = {
+const struct attribute_group qeth_device_blkt_group = {
 	.name = "blkt",
 	.attrs = qeth_blkt_device_attrs,
 };
+EXPORT_SYMBOL_GPL(qeth_device_blkt_group);
 
 static struct attribute *qeth_device_attrs[] = {
 	&dev_attr_state.attr,
@@ -728,9 +733,10 @@ static struct attribute *qeth_device_attrs[] = {
 	&dev_attr_switch_attrs.attr,
 	NULL,
 };
-static struct attribute_group qeth_device_attr_group = {
+const struct attribute_group qeth_device_attr_group = {
 	.attrs = qeth_device_attrs,
 };
+EXPORT_SYMBOL_GPL(qeth_device_attr_group);
 
 const struct attribute_group *qeth_generic_attr_groups[] = {
 	&qeth_device_attr_group,

drivers/s390/net/qeth_l2.h

@@ -8,6 +8,8 @@
 
 #include "qeth_core.h"
 
+extern const struct attribute_group *qeth_l2_attr_groups[];
+
 int qeth_l2_create_device_attributes(struct device *);
 void qeth_l2_remove_device_attributes(struct device *);
 void qeth_l2_setup_bridgeport_attrs(struct qeth_card *card);

drivers/s390/net/qeth_l2_main.c

@@ -880,14 +880,21 @@ static int qeth_l2_stop(struct net_device *dev)
 	return 0;
 }
 
+static const struct device_type qeth_l2_devtype = {
+	.name = "qeth_layer2",
+	.groups = qeth_l2_attr_groups,
+};
+
 static int qeth_l2_probe_device(struct ccwgroup_device *gdev)
 {
 	struct qeth_card *card = dev_get_drvdata(&gdev->dev);
 	int rc;
 
-	rc = qeth_l2_create_device_attributes(&gdev->dev);
-	if (rc)
-		return rc;
+	if (gdev->dev.type == &qeth_generic_devtype) {
+		rc = qeth_l2_create_device_attributes(&gdev->dev);
+		if (rc)
+			return rc;
+	}
 	INIT_LIST_HEAD(&card->vid_list);
 	hash_init(card->mac_htable);
 	card->options.layer2 = 1;
@@ -899,7 +906,8 @@ static void qeth_l2_remove_device(struct ccwgroup_device *cgdev)
 {
 	struct qeth_card *card = dev_get_drvdata(&cgdev->dev);
 
-	qeth_l2_remove_device_attributes(&cgdev->dev);
+	if (cgdev->dev.type == &qeth_generic_devtype)
+		qeth_l2_remove_device_attributes(&cgdev->dev);
 	qeth_set_allowed_threads(card, 0, 1);
 	wait_event(card->wait_q, qeth_threads_running(card, 0xffffffff) == 0);
 
@@ -1272,6 +1280,7 @@ static int qeth_l2_control_event(struct qeth_card *card,
 }
 
 struct qeth_discipline qeth_l2_discipline = {
+	.devtype = &qeth_l2_devtype,
 	.start_poll = qeth_qdio_start_poll,
 	.input_handler = (qdio_handler_t *) qeth_qdio_input_handler,
 	.output_handler = (qdio_handler_t *) qeth_qdio_output_handler,

drivers/s390/net/qeth_l2_sys.c

@@ -269,3 +269,11 @@ void qeth_l2_setup_bridgeport_attrs(struct qeth_card *card)
 	} else
 		qeth_bridgeport_an_set(card, 0);
 }
+
+const struct attribute_group *qeth_l2_attr_groups[] = {
+	&qeth_device_attr_group,
+	&qeth_device_blkt_group,
+	/* l2 specific, see l2_{create,remove}_device_attributes(): */
+	&qeth_l2_bridgeport_attr_group,
+	NULL,
+};

drivers/s390/net/qeth_l3_main.c

@@ -3309,6 +3309,7 @@ static int qeth_l3_control_event(struct qeth_card *card,
 }
 
 struct qeth_discipline qeth_l3_discipline = {
+	.devtype = &qeth_generic_devtype,
 	.start_poll = qeth_qdio_start_poll,
 	.input_handler = (qdio_handler_t *) qeth_qdio_input_handler,
 	.output_handler = (qdio_handler_t *) qeth_qdio_output_handler,