A common pattern with skb_put() is to just want to memcpy()
some data into the new space, introduce skb_put_data() for
this.
An spatch similar to the one for skb_put_zero() converts many
of the places using it:
@@
identifier p, p2;
expression len, skb, data;
type t, t2;
@@
(
-p = skb_put(skb, len);
+p = skb_put_data(skb, data, len);
|
-p = (t)skb_put(skb, len);
+p = skb_put_data(skb, data, len);
)
(
p2 = (t2)p;
-memcpy(p2, data, len);
|
-memcpy(p, data, len);
)
@@
type t, t2;
identifier p, p2;
expression skb, data;
@@
t *p;
...
(
-p = skb_put(skb, sizeof(t));
+p = skb_put_data(skb, data, sizeof(t));
|
-p = (t *)skb_put(skb, sizeof(t));
+p = skb_put_data(skb, data, sizeof(t));
)
(
p2 = (t2)p;
-memcpy(p2, data, sizeof(*p));
|
-memcpy(p, data, sizeof(*p));
)
@@
expression skb, len, data;
@@
-memcpy(skb_put(skb, len), data, len);
+skb_put_data(skb, data, len);
(again, manually post-processed to retain some comments)
Reviewed-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
There were many places that my previous spatch didn't find,
as pointed out by yuan linyu in various patches.
The following spatch found many more and also removes the
now unnecessary casts:
@@
identifier p, p2;
expression len;
expression skb;
type t, t2;
@@
(
-p = skb_put(skb, len);
+p = skb_put_zero(skb, len);
|
-p = (t)skb_put(skb, len);
+p = skb_put_zero(skb, len);
)
... when != p
(
p2 = (t2)p;
-memset(p2, 0, len);
|
-memset(p, 0, len);
)
@@
type t, t2;
identifier p, p2;
expression skb;
@@
t *p;
...
(
-p = skb_put(skb, sizeof(t));
+p = skb_put_zero(skb, sizeof(t));
|
-p = (t *)skb_put(skb, sizeof(t));
+p = skb_put_zero(skb, sizeof(t));
)
... when != p
(
p2 = (t2)p;
-memset(p2, 0, sizeof(*p));
|
-memset(p, 0, sizeof(*p));
)
@@
expression skb, len;
@@
-memset(skb_put(skb, len), 0, len);
+skb_put_zero(skb, len);
Apply it to the tree (with one manual fixup to keep the
comment in vxlan.c, which spatch removed.)
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
To support HT and VHT CSA, beacons and action frames must include the
corresponding IEs.
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
[make ieee80211_ie_build_wide_bw_cs() return void]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Have proper request id filled in the SCHED_SCAN_RESULTS and
SCHED_SCAN_STOPPED notifications toward user-space by having the
driver provide it through the api.
Reviewed-by: Hante Meuleman <hante.meuleman@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieter-paul.giesberts@broadcom.com>
Reviewed-by: Franky Lin <franky.lin@broadcom.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Parse the BSS max idle period element and set the BSS configuration
accordingly so the driver can use this information to configure the
max idle period and to use protected management frames for keep alive
when required.
The BSS max idle period element is defined in IEEE802.11-2016,
section 9.4.2.79
Signed-off-by: Avraham Stern <avraham.stern@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Existing API 'ieee80211_get_sdata_band' returns default 2 GHz band even
if the channel context configuration is NULL. This crashes for chipsets
which support 5 Ghz alone when it tries to access members of 'sband'.
Channel context configuration can be NULL in multivif case and when
channel switch is in progress (or) when it fails. Fix this by replacing
the API 'ieee80211_get_sdata_band' with 'ieee80211_get_sband' which
returns a NULL pointer for sband when the channel configuration is NULL.
An example scenario is as below:
In multivif mode (AP + STA) with drivers like ath10k, when we do a
channel switch in the AP vif (which has a number of clients connected)
and a STA vif which is connected to some other AP, when the channel
switch in AP vif fails, while the STA vifs tries to connect to the
other AP, there is a window where the channel context is NULL/invalid
and this results in a crash while the clients connected to the AP vif
tries to reconnect and this race is very similar to the one investigated
by Michal in https://patchwork.kernel.org/patch/3788161/ and this does
happens with hardware that supports 5Ghz alone after long hours of
testing with continuous channel switch on the AP vif
ieee80211 phy0: channel context reservation cannot be finalized because
some interfaces aren't switching
wlan0: failed to finalize CSA, disconnecting
wlan0-1: deauthenticating from 8c:fd:f0:01:54:9c by local choice
(Reason: 3=DEAUTH_LEAVING)
WARNING: CPU: 1 PID: 19032 at net/mac80211/ieee80211_i.h:1013 sta_info_alloc+0x374/0x3fc [mac80211]
[<bf77272c>] (sta_info_alloc [mac80211])
[<bf78776c>] (ieee80211_add_station [mac80211]))
[<bf73cc50>] (nl80211_new_station [cfg80211])
Unable to handle kernel NULL pointer dereference at virtual
address 00000014
pgd = d5f4c000
Internal error: Oops: 17 [#1] PREEMPT SMP ARM
PC is at sta_info_alloc+0x380/0x3fc [mac80211]
LR is at sta_info_alloc+0x37c/0x3fc [mac80211]
[<bf772738>] (sta_info_alloc [mac80211])
[<bf78776c>] (ieee80211_add_station [mac80211])
[<bf73cc50>] (nl80211_new_station [cfg80211]))
Cc: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Mohammed Shafi Shajakhan <mohammed@qti.qualcomm.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This field will need to be used again for HE, so rename it now.
Again, mostly done with this spatch:
@@
expression status;
@@
-status->vht_nss
+status->nss
@@
expression status;
@@
-status.vht_nss
+status.nss
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
At least on iwlwifi, sometimes lockdep complains that we can
lock
chanctx_mtx -> mvm.mutex -> iflist_mtx
(due to iterate_interfaces)
and
iflist_mtx -> chanctx_mtx
Remove the latter dependency in mac80211 by using the RTNL
that we already hold in one case, and can relatively easily
achieve in the other case.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This matches the spec, and otherwise things are really
confusing with the next patch adding CCFS2.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
As part of interface combination checking, verify any new
interface's beacon intervals. In fact, just always add the
beacon interval since that's harmless.
With this patch, mac80211 is prepared for drivers that set
the min_beacon_int_gcd parameter in interface combinations.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
The uapsd_queue field is in QoS IE order and not in
IEEE80211_AC_*'s order.
This means that mac80211 would get confused between
BK and BE which is certainly not such a big deal but
needs to be fixed.
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Move the growing parameter list to a structure for the interface
combination check and iteration functions in cfg80211 and mac80211
to make the code easier to understand.
Signed-off-by: Purushottam Kushwaha <pkushwah@qti.qualcomm.com>
[edit commit message]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
The TXQ intermediate queues can cause packet reordering when more than
one flow is active to a single station. Since some of the wifi-specific
packet handling (notably sequence number and encryption handling) is
sensitive to re-ordering, things break if they are applied before the
TXQ.
This splits up the TX handlers and fast_xmit logic into two parts: An
early part and a late part. The former is applied before TXQ enqueue,
and the latter after dequeue. The non-TXQ path just applies both parts
at once.
Because fragments shouldn't be split up or reordered, the fragmentation
handler is run after dequeue. Any fragments are then kept in the TXQ and
on subsequent dequeues they take precedence over dequeueing from the FQ
structure.
This approach avoids having to scatter special cases all over the place
for when TXQ is enabled, at the cost of making the fast_xmit and TX
handler code slightly more complex.
Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
[fix a few code-style nits, make ieee80211_xmit_fast_finish void,
remove a useless txq->sta check]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Implement add/rm_nan_func functions and handle NAN function
termination notifications. Handle instance_id allocation for
NAN functions and implement the reconfig flow.
Signed-off-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This code doesn't do much besides allowing to start and
stop the vif.
Signed-off-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Ayala Beker <ayala.beker@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This allows user space to start/stop NAN interface.
A NAN interface is like P2P device in a few aspects: it
doesn't have a netdev associated to it.
Add the new interface type and prevent operations that
can't be executed on NAN interface like scan.
Define several attributes that may be configured by user space
when starting NAN functionality (master preference and dual
band operation)
Signed-off-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
The next line overwrites this assignment, so remove it; there's
no real value in using it for the next assignment either.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Insert the u32 monitor flags variable in a new structure
that represents a monitor interface.
This will allow to add more configuration variables to
that structure which will happen in an upcoming change.
Signed-off-by: Aviya Erenfeld <aviya.erenfeld@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
mac80211's software queues were designed to work
very closely with device tx queues. They are
required to make use of 802.11 packet aggregation
easily and efficiently.
Due to the way 802.11 aggregation is designed it
only makes sense to keep fair queuing as close to
hardware as possible to reduce induced latency and
inertia and provide the best flow responsiveness.
This change doesn't translate directly to
immediate and significant gains. End result
depends on driver's induced latency. Best results
can be achieved if driver keeps its own tx
queue/fifo fill level to a minimum.
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Qdiscs are designed with no regard to 802.11
aggregation requirements and hand out
packet-by-packet with no guarantee they are
destined to the same tid. This does more bad than
good no matter how fairly a given qdisc may behave
on an ethernet interface.
Software queuing used per-AC netdev subqueue
congestion control whenever a global AC limit was
hit. This meant in practice a single station or
tid queue could starve others rather easily. This
could resonate with qdiscs in a bad way or could
just end up with poor aggregation performance.
Increasing the AC limit would increase induced
latency which is also bad.
Disabling qdiscs by default and performing
taildrop instead of netdev subqueue congestion
control on the other hand makes it possible for
tid queues to fill up "in the meantime" while
preventing stations starving each other.
This increases aggregation opportunities and
should allow software queuing based drivers
achieve better performance by utilizing airtime
more efficiently with big aggregates.
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This enum is already perfectly aliased to enum nl80211_band, and
the only reason for it is that we get IEEE80211_NUM_BANDS out of
it. There's no really good reason to not declare the number of
bands in nl80211 though, so do that and remove the cfg80211 one.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
When HW crypto is used, there's no need for the CCMP/GCMP MIC to
be available to mac80211, and the hardware might have removed it
already after checking. The MIC is also useless to have when the
frame is already decrypted, so allow indicating that it's not
present.
Since we are running out of bits in mac80211_rx_flags, make
the flags field a u64.
Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Drivers may need to track which vif is using VHT MU-MIMO.
Move the flag indicationg the ownership of MU_MIMO to
ieee80211_vif.
Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Number of deployed 80 MHz capable VHT stations that do not support 80+80
and 160 MHz bandwidths seem to misbehave when trying to connect to an AP
that advertises 80+80 or 160 MHz channel bandwidth in the VHT Operation
element. To avoid such issues with deployed devices, modify the design
based on recently accepted IEEE 802.11 standard changes (*).
This allows poorly implemented VHT 80 MHz stations to connect with the
AP in 80 MHz mode. 80+80 and 160 MHz capable stations need to support
the new workaround mechanism to allow full bandwidth to be used.
However, there are more or less no impacted station with 80+80/160
capability deployed.
The rebased version of this patch is based on the updated version from
Johannes Berg to take the HT/VHT chandef refactoring into account.
(*) Changes in
https://mentor.ieee.org/802.11/dcn/15/11-15-1530-04-000m-vht160-operation-signaling-through-non-zero-ccfs1.docx
were accepted during the IEEE 802.11 January 2016 meeting.
Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This will allow drivers to make more educated
decisions whether to defer transmission or not.
Relying on wake_tx_queue() call count implicitly
was not possible because it could be called
without queued frame count actually changing on
software tx aggregation start/stop code paths.
It was also not possible to know how long
byte-wise queue was without dequeueing.
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
The timestamp given by iwlwifi is at the beginning of the
frame over the air, at (or during) the SYNC field. Allow
such timestamps to be given to mac80211, at least (for now)
for frames with non-HT/VHT preambles.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
The station MLME and IBSS/mesh ones use entirely different
code for interpreting HT and VHT operation elements. Change
the code that interprets them a bit - it now modifies an
existing chandef - and use it also in the MLME code.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
The Group ID Management frame is an Action frame of
category VHT. It is transmitted by the AP to assign
or change the user position of a STA for one or more
group IDs.
Process and save the group membership data. Notify
underlying driver of changes.
Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
On reconfig, in case of sched_scan_req->n_scan_plans > 1,
local->sched_scan_req was never cleared, although
cfg80211_sched_scan_stopped_rtnl() was called, resulting
in local->sched_scan_req holding a stale and preventing
further scheduled scan requests.
Clear it explicitly in this case.
Fixes: 42a7e82c6792 ("mac80211: Do not restart scheduled scan if multiple scan plans are set")
Signed-off-by: Eliad Peller <eliadx.peller@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Defer ROC requests during hw restart, as the driver
might not be fully configured in this stage (e.g.
channel contexts were not added yet)
Signed-off-by: Eliad Peller <eliadx.peller@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Conflicts:
drivers/net/geneve.c
Here we had an overlapping change, where in 'net' the extraneous stats
bump was being removed whilst in 'net-next' the final argument to
udp_tunnel6_xmit_skb() was being changed.
Signed-off-by: David S. Miller <davem@davemloft.net>
During reprogramming, mac80211 currently first adds all the channel
contexts, then binds them to the vifs and then goes to reconfigure
all the interfaces. Drivers might, perhaps implicitly, rely on the
operation order for certain things that typically happen within a
single function elsewhere in mac80211. To avoid problems with that,
reorder the code in mac80211's restart/reprogramming to work fully
within the interface loop so that the order of operations is like
in normal operation.
For iwlwifi, this fixes a firmware crash when reprogramming with an
AP/GO interface active.
Reported-by: David Spinadel <david.spinadel@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
When reconfiguration during resume fails while a scan is pending
for completion work, that work will never run, and the scan will
be stuck forever. Factor out the code to recover this and call it
also in ieee80211_handle_reconfig_failure().
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
If some code stops the queues more times than having started
(for when refcounting is used), warn on and reset the counter
to 0 to avoid blocking forever.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
The function currently determines this value, for use in bss_info.qos,
based on the interface type itself. Make it a parameter instead and
set it with the same logic for now.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
When 11n peers performs a TDLS connection on a legacy BSS, the HT
operation IE must be specified according to IEEE802.11-2012 section
9.23.3.2. Otherwise HT-protection is compromised and the medium becomes
noisy for both the TDLS and the BSS links.
Signed-off-by: Arik Nemtsov <arikx.nemtsov@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Scheduled scan has to be reconfigured only if wowlan wasn't
configured, since otherwise it should continue to run (with
the 'any' trigger) or be aborted.
The current code will end up asking the driver to start a new
scheduled scan without stopping the previous one, and leaking
some memory (from the previous request.)
Fix this by doing the abort/restart under the proper conditions.
Signed-off-by: Eliad Peller <eliadx.peller@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
If drv_start() fails during hw_restart, all the running
interfaces are being closed/stopped, which results in
drv_stop() being called, although the driver was never
started successfully.
This might cause drivers to perform operations on uninitialized
memory (as they assume it was initialized on drv_start)
Consider the local->started flag, and call the driver's stop()
op only if drv_start() succeeded before.
Move drv_start() and drv_stop() to driver-ops.c, as they are no
longer simple wrappers.
Signed-off-by: Eliad Peller <eliadx.peller@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
The recalc_smps work can run after the station disassociates.
At this stage we already released the channel, but the work
will be cancelled only when the interface stops.
In this scenario we can hit the warning in ieee80211_recalc_smps, so
just remove it.
Signed-off-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Requesting hw restart during suspend might result
in the restart work being executed after mac80211
and the hw are suspended.
Solve the race by simply scheduling the restart
work on a freezable workqueue.
Note that there can be some cases of reconfiguration
on resume (besides the hardware restart):
* wowlan is not configured -
All the interfaces removed were removed on suspend,
and drv_stop() was called. At this point the driver
shouldn't expect for hw_restart anyway, so we can
simply cancel it (on resume).
* wowlan is configured, drv_resume() == 1
There is no definitive expected behavior in this case,
as each driver might have different expectations (e.g.
setting some flags on suspend/restart vs. not handling
spurious recovery).
For now, simply let the hw_restart work run again after
resume, and hope the driver will handle it well (or at
least initiate another hw restart).
Signed-off-by: Eliad Peller <eliadx.peller@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
In case of one shot NOA the interval can be 0, catch that
instead of potentially (depending on the driver) crashing
like this:
divide error: 0000 [#1] SMP
[...]
Call Trace:
<IRQ>
[<ffffffffc08e891c>] ieee80211_extend_absent_time+0x6c/0xb0 [mac80211]
[<ffffffffc08e8a17>] ieee80211_update_p2p_noa+0xb7/0xe0 [mac80211]
[<ffffffffc069cc30>] ath9k_p2p_ps_timer+0x170/0x190 [ath9k]
[<ffffffffc070adf8>] ath_gen_timer_isr+0xc8/0xf0 [ath9k_hw]
[<ffffffffc0691156>] ath9k_tasklet+0x296/0x2f0 [ath9k]
[<ffffffff8107ad65>] tasklet_action+0xe5/0xf0
[...]
Cc: stable@vger.kernel.org [3.16+, due to d463af4a1c using it]
Signed-off-by: Janusz Dziedzic <janusz.dziedzic@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
As this API has never really seen any use and most drivers don't
ever use the value derived from it, remove it.
Change the only driver using it (rt2x00) to simply use the DTIM
period instead of the "max sleep" time.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
If multiple scan plans were set for scheduled scan, do not restart
scheduled scan on reconfig because it is possible that some scan
plans were already completed and there is no need to run them all
over again. Instead, notify userspace that scheduled scan stopped
so it can configure new scan plans for scheduled scan.
Signed-off-by: Avraham Stern <avraham.stern@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Instead of int with 0/1, use bool with false/true for the
powersave argument to ieee80211_send_nullfunc().
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
In case of "any" wowlan trigger, there is no reason to tear down
aggregations, as we want the device to continue working normally.
Similarly, there's no reason to tear down aggregations on resume,
as they should have been torn down on suspend if needed.
However, since the reconfiguration flow is shared with HW restart,
tear down aggregations on reconfiguration when we are not resuming.
To keep things working after non-wowlan suspend, keep clearing the
WLAN_STA_BLOCK_BA flag.
Signed-off-by: Eliad Peller <eliadx.peller@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
It doesn't seem problematic to change the weight for the average
beacon signal from 3 to 4, so use DECLARE_EWMA. This also makes
the code easier to maintain since bugs like the one fixed in the
previous patch can't happen as easily.
With a fix from Avraham Stern to invert the sign since EMWA uses
unsigned values only.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
