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s390/qeth: allow cmd callbacks to return errnos
Error propagation from cmd callbacks currently works in a way where
qeth_send_control_data_cb() picks the raw HW code from the response,
and the cmd's originator later translates this into an errno.
The callback itself only returns 0 ("done") or 1 ("expect more data").
This is
1. limiting, as the only means for the callback to report an internal
error is to invent pseudo HW codes (such as IPA_RC_ENOMEM), that
the originator then needs to understand. For non-IPA callbacks, we
even provide a separate field in the IO buffer metadata (iob->rc) so
the callback can pass back a return value.
2. fragile, as the originator must take care to not translate any errno
that is returned by qeth's own IO code paths (eg -ENOMEM). Also, any
originator that forgets to translate the HW codes potentially passes
garbage back to its caller. For instance, see
commit 2aa48671 ("s390/qeth: translate SETVLAN/DELVLAN errors").
Introduce a new model where all HW error translation is done within the
callback, and the callback returns
> 0, if it expects more data (as before)
== 0, on success
< 0, with an errno
Start off with converting all callbacks to the new model that either
a) pass back pseudo HW codes, or b) have a dependency on a specific
HW error code. Also convert c) the one callback that uses iob->rc, and
d) qeth_setadpparms_change_macaddr_cb() so that it can pass back an
error back to qeth_l2_request_initial_mac() even when the cmd itself
was successful.
The old model remains supported: if the callback returns 0, we still
propagate the response's HW error code back to the originator.
Signed-off-by: 
Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>