Jean,
Jean Tourrilhes wrote:
I must admit that the original definition was too clever (or
too ambiguous, or too original, take your pick). range->max_qual.level
is always supposed to have a meaningfull value. People that did not
understand that original definition just put 0 there, as it was the
easiest way to output dBm.
If you want more details, check the comment in the function
iw_print_stats() in iwlib.c.
As I say, range->max_qual.level is always supposed to have
something useful, so :
if(IW_QUAL_DBM == 0)
rssi level in the range [0 ; range->max_qual.level]
if(IW_QUAL_DBM == 1)
(rssi level - 256) in the range [range->max_qual.level - 256 ; 0]
Thank you for your explanation and the reference to the comment from wireless_tools. I think it is
safe to say that we all have learned a lot. As you say, 8-bit arithmetic is tricky.
I think WE-19 is old enough (most distro seems to use 2.6.16)
that we don't have to bother about earlier version going forward.
I'm going to rely on that, set IW_QUAL_DBM, and choose the max_qual at 152, which corresponds to a
floor-value of -104 dBm. The KDE applet display is a little strange as it displays -65 dBm at
approximately 2/3 height, rather than the 1/3 value that I would expect. So far, I have not found
the source for that applet and cannot verify the calculation. In any case, the display is acceptable
even if not what I would expect. At least, the values in /proc/net/wireless are correct.
Thanks again,
Larry
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