• Julian Wiedmann's avatar
    s390/qeth: unbreak OSM and OSN support · 2d2ebb3e
    Julian Wiedmann authored
    commit b4d72c08 ("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: b4d72c08 ("qeth: bridgeport support - basic control")
    Signed-off-by: default avatarJulian Wiedmann <jwi@linux.vnet.ibm.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    2d2ebb3e
qeth_l2_sys.c 6.54 KB