Re: Signal quality strange since commit 708c57cf1709fb95

[Dan Williams <dcbw@redhat.com>]

On Sat, 2009-02-21 at 09:09 -0600, Larry Finger wrote:
> I admit that I didn't follow the discussion of reporting signal quality very
> closely; however since commit 708c57cf1709fb95, all of my wireless devices (b43,
> p54usb, rtl8187) are reporting link quality as XX/70 rather than XX/100. I doubt
> that this was an intended consequence of that patch. If the SIOCGIWRANGE ioctl
> is now more correct, what changes are needed in the drivers to restore the old
> behavior? Having written the qual calculation for 2 drivers, I understand the
> uselessness of this number, but I also know the uproar such a change will cause
> in the user community.

Intended.  It doesn't matter what the /X number is; it's simply the
upper bound of what the # before the / will be.  Quality is in the range
of [0 ... max_qual.qual].  You should be able to divide quality /
max_qual.qual and get a reasonable number to use for pretty UI display.

Many drivers used to use something other than 100 for max quality, and
many still do:

airo.c:		range->max_qual.qual = airo_get_max_quality(&cap_rid);
hostap/hostap_ioctl.c:		range->max_qual.qual = 70; /* what is correct max? This was not
hostap/hostap_ioctl.c:		range->max_qual.qual = 92; /* 0 .. 92 */
netwave_cs.c:	range->max_qual.qual = 255;
orinoco/wext.c:		range->max_qual.qual = 0x8b - 0x2f;
wavelan.c:	range->max_qual.qual = MMR_SGNL_QUAL;
wavelan_cs.c:	range->max_qual.qual = MMR_SGNL_QUAL;
zd1201.c:	range->max_qual.qual = 128;

Dan