On 11/04/2015 11:56 PM, Johannes Berg wrote:
On Thu, 2015-11-05 at 07:41 +0100, Michal Kazior wrote:
On 5 November 2015 at 00:58, Ben Greear <greearb@xxxxxxxxxxxxxxx>
wrote:
It looks to me like the channel dwell time when scanning (SW
scanning,
mac80211)
is fixed at 1/9 of a second. I'd like to make this
configurable...is that
something
that might be welcome upstream?
My plan is to add to the netlink API around starting a scan and
allow
user-space to
configure a dwell time in milliseconds.
I've actually tried doing something like this some time ago:
- http://thread.gmane.org/gmane.linux.kernel.wireless.general/111255
- http://thread.gmane.org/gmane.linux.kernel.wireless.general/111251
And as I said back then, I'm rather opposed to this. We risk adding API
that either nobody uses, or that ends up getting used in ways that
weren't intended (say for certain measurements) and then will break
things when scanning is changed in firmware, etc.
Let the scanning be. It's intended to find networks, not really
something else. Piggy-backing survey onto it was mostly a mistake. For
other things, do some more reasonable measurement commands.
My issue is that APs can be set to beacon at longer beacon times, and
then passive scanning at ~110ms intervals is not going to find the APs
very often (and with bad luck, technically it could *never* find the AP
due to scanning at unlucky periodic intervals).
So, when I know that I am doing passive scan, I would like the option
to set the dwell time larger.
And, for active scanning, maybe 33ms is a lot longer that is actually
needed?
I read through some of your comments from before. I think we could
treat this as a hint to the driver, and it could ignore it as needed.
Firmware implementations I'm aware of are already limited in a million
different ways, and of course if someone cared, they could propagate
the dwell time into the firmware if they cared.
Thanks,
Ben
--
Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc http://www.candelatech.com
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