CVS-2-2 ipw2200 NMApplet bar empty patch

[Bill Moss <bmoss clemson edu>]

The function nm_wireless_qual_to_percent has a pointer to the max_qual 
structure as its second argument. In the ipw2200 driver

max_qual->qual = 100;
max_qual->level = 0;
max_qual->noise=0;

I changed this to

max_qual->qual = 100;
max_qual->level = PERFECT_RSSI + 0x100;
max_qual->noise = WORST_RSSI + 0x100;

The second two values are biased dBm values. Each driver has its own way 
to compute percentage from RSSI values. Formulas vary based on the units 
RSSI is measure in. In some cases a lookup table is used. To get a rough 
indicator of percentage signal level for use in the NMApplet bar, I 
modified the
nm_wireless_qual_to_percent function as indicated below. Now the 
NMApplet hover gives percentage values consistent with what I get from 
iwconfig for the associated AP and the NMApplet bars show for each 
scanned AP an approximate signal level. My percentage signal level 
formula is a linear model which underestimates the signal level say in 
comparison to the values that Windows XP reports. If a driver does not 
set max_qual->level and max_qual->noise, the nm_wireless_qual_to_percent 
function could make some guesses.

RSSI in dBm is measuring a real physical quantity power. Percentage 
signal level is a man made device. I wonder what value it really has. If 
you are doing a building site map say for 80211B, what you really want 
to do is to find the 11Mbps areas, the 5.5Mpbs areas, the 2Mbps areas, 
and the 1 Mbps areas. This type of information gives the user an 
indication of throughput which is more useful than a percent. What the 
heck does 80% mean in the wireless world across drivers -- next to nothing.

/* Try using the card's idea of the signal quality first as long as it 
tells us what the max quality is */
if ((qual->qual != 0) && (max_qual->qual != 0) && !(max_qual->updated & 
IW_QUAL_QUAL_INVALID) && !(qual->up
dated & IW_QUAL_QUAL_INVALID))
       {
               percent = (int)(100 * ((double)qual->qual / 
(double)max_qual->qual));
       }
       else
       {
               if ((qual->level !=0) && (max_qual->level !=0) && 
(max_qual->noise !=0))
               {
                       percent = (int)(100 - 70*(
                               ((double)max_qual->level - 
(double)qual->level) /
                               ((double)max_qual->level - 
(double)max_qual->noise)));
               }
               else if ((qual->level > max_qual->level) && (qual->noise 
!= 0))

--
Bill Moss
Professor, Mathematical Sciences
Clemson University