mac80211: use hardware flags for signal/noise units

trying to clean up the signal/noise code. the previous code in mac80211 had
confusing names for the related variables, did not have much definition of
what units of signal and noise were provided and used implicit mechanisms from
the wireless extensions.

this patch introduces hardware capability flags to let the hardware specify
clearly if it can provide signal and noise level values and which units it can
provide. this also anticipates possible new units like RCPI in the future.

for signal:

  IEEE80211_HW_SIGNAL_UNSPEC - unspecified, unknown, hw specific
  IEEE80211_HW_SIGNAL_DB     - dB difference to unspecified reference point
  IEEE80211_HW_SIGNAL_DBM    - dBm, difference to 1mW

for noise we currently only have dBm:

  IEEE80211_HW_NOISE_DBM     - dBm, difference to 1mW

if IEEE80211_HW_SIGNAL_UNSPEC or IEEE80211_HW_SIGNAL_DB is used the driver has
to provide the maximum value (max_signal) it reports in order for applications
to make sense of the signal values.

i tried my best to find out for each driver what it can provide and update it
but i'm not sure (?) for some of them and used the more conservative guess in
doubt. this can be fixed easily after this patch has been merged by changing
the hardware flags of the driver.

DRIVER          SIGNAL    MAX	NOISE   QUAL
-----------------------------------------------------------------
adm8211         unspec(?) 100   n/a     missing
at76_usb        unspec(?) (?)   unused  missing
ath5k           dBm             dBm     percent rssi
b43legacy       dBm             dBm     percent jssi(?)
b43             dBm             dBm     percent jssi(?)
iwl-3945        dBm             dBm     percent snr+more
iwl-4965        dBm             dBm     percent snr+more
p54             unspec    127   n/a     missing
rt2x00          dBm	        n/a     percent rssi+tx/rx frame success
  rt2400        dBm             n/a
  rt2500pci     dBm             n/a
  rt2500usb     dBm             n/a
  rt61pci       dBm             n/a
  rt73usb       dBm             n/a
rtl8180         unspec(?) 65    n/a     (?)
rtl8187         unspec(?) 65    (?)     noise(?)
zd1211          dB(?)     100   n/a     percent

drivers/net/wireless/ath5k/base.c:      Changes-licensed-under: 3-Clause-BSD

Signed-off-by: Bruno Randolf <br1@einfach.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index 97a61c39ad90..e89cc1655547 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -216,8 +216,8 @@ struct sta_info {
 				       * from this STA */
 	unsigned long rx_fragments; /* number of received MPDUs */
 	unsigned long rx_dropped; /* number of dropped MPDUs from this STA */
-	int last_rssi; /* RSSI of last received frame from this STA */
 	int last_signal; /* signal of last received frame from this STA */
+	int last_qual;  /* qual of last received frame from this STA */
 	int last_noise; /* noise of last received frame from this STA */
 	/* last received seq/frag number from this STA (per RX queue) */
 	__le16 last_seq_ctrl[NUM_RX_DATA_QUEUES];