kern/55428: run(4) signal strength indication is backwards

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         55428
>Category:       kern
>Synopsis:       run(4) signal strength indication is backwards
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Jun 28 11:15:00 +0000 2020
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current 9.99.59
>Organization:
>Environment:
System: NetBSD
Architecture: i386
Machine: i386
>Description:

Attaching a USB WiFi adapter supported by the run(4) driver and
running "ifconfig run0 list scan", the signal strength reported
in the "S" part of the "S:N" column increases when I move the
adapter and access point further apart, and decreases when I move
them closer.  I would expect it to be the other way round.

Here is output from multiple runs of "ifconfig run0 list scan", edited
to remove duplicate column headers and unrelated access points, and
annotated with the approximate distance to the access point in square
brackets at the end of each line:

  SSID              BSSID              CHAN RATE  S:N     INT CAPS
  test              78:6a:89:5b:06:12    1   54M  45:0    100 E    WME [10 m]
  test              78:6a:89:5b:06:12    1   54M  19:0    100 E    WME  [2 m]
  test              78:6a:89:5b:06:12    1   54M  17:0    100 E    WME  [1 m]
  test              78:6a:89:5b:06:12    1   54M  15:0    100 E    WME  [50 cm]
  test              78:6a:89:5b:06:12   11   54M   9:0    100 E    WME  [20 cm]

At very close distance (a few centimeters), the signal strength
value appears to wrap around from 0 to 255:

  test              78:6a:89:5b:06:12   11   54M 251:0    100 E    WME  [10 cm]

Here is dmesg output for the adapter in case:

  run0: Ralink (0x148f) 802.11 n WLAN (0x3070), rev 2.00/1.01, addr 2
  run0: MAC/BBP RT3070 (rev 0x0201), RF RT3020 (MIMO 1T1R), address 00:e0:4c:b8:16:5e

I'm also getting similar results with another, newer adapter:

  run0: Ralink (0x148f) 802.11 n WLAN (0x5370), rev 2.00/1.01, addr 2
  run0: MAC/BBP RT5390 (rev 0x0502), RF RT5370 (MIMO 1T1R), address 00:e1:27:01:1e:53

>How-To-Repeat:

>Fix: