Problem with BSS properties

Dan Williams dcbw
Fri Dec 25 15:07:17 PST 2009

On Sat, 2009-12-26 at 01:51 +0100, Witold Sowa wrote:
> Marcel Holtmann pisze:
> >> Jouni was worried of excessive memory usage on embedded devices, but
> >> these doesn't use DBus interface. Am I right? I would assume that a
> >> system which use wpa_supplicant with DBus interface has quite a lof of
> >> RAM and a few additional KBs (even more than 100kB in worst case)
> >> shouldn't be a problem. We would copy whole previous scan results but
> >> keep in in DBus code (i.e. within #ifdef CONFIG_CTRL_IFACE_DBUS_NEW).
> >> That would make code a bit less clean, but we would be able to compare
> >> all BSS properties, and Jouni would be happy having limited memory usage.
> > 
> > I can see the point of the extra memory usage, but what can we do. For
> > every device with any kind of visual user interface, we have to keep the
> > values somewhere. And I prefer to have these change notification inside
> > wpa_supplicant instead of complicating the client code.
> > 
> I agree - we want to have notifications inside wpa_supplicant. What I
> meant was to keep two scan results at the same time only when DBus
> support is enabled on compilation time so we won't waste memory when no
> DBus interface is available.

If we really want a complete D-Bus interface, we *have* to keep both old
+ new around to take a difference between the two and push out the
PropertiesChanged signal.  I don't really know what Jouni will think
about that, but I don't see any other way to get a complete change list
(including IEs, which are the major memory user).

While IEs are nice to have, if Jouni is really concerned about memory
usage we can ignore IE changes for now and just do limited set of
properties.  But eventually I think we pretty much need everything.


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