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>

1 files changed, 14 insertions, 8 deletions

diff --git a/drivers/s390/net/qeth_core_sys.c b/drivers/s390/net/qeth_core_sys.c
index 412ff61891ac..db6a285d41e0 100644
--- a/drivers/s390/net/qeth_core_sys.c
+++ b/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,