Re: [PATCH] cfg80211: fix WEXT ioctl GIWFREQ for monitor interfaces

[Johannes Berg <johannes@sipsolutions.net>]

On Tue, 2010-07-20 at 01:28 +0200, David Gnedt wrote:
> Am 2010-07-19 23:06, schrieb Gábor Stefanik:
> > (BTW, I say that a GIWFREQ on a monitor interface should always return
> > the channel the PHY is tuned to at the moment when it is issued. Most
> > tools seem to expect this behavior.)
> 
> I agree, that would be the expected behaviour.
> 
> I am not very familar with the entire wireless subsystem yet, but wouldn't that
> imply a interface change in cfg80211 and mac80211 to add an "get_channel" function?

Yes, I think so.

> Because if the card is hopping channels (e.g. because of 2 station interfaces on
> different channels), only the driver itself can tell what's really the current
> channel.

Right. Although in that case I'm not sure we should be telling userspace
what channel the monitor interface is on, since there's no single
channel it is on, and I certainly hope userspace won't be requesting the
channel many times per second!

> Nevertheless a default implementation for this new "get_channel" can be written
> at mac80211 level (or even cfg80211?), which tries to find the current channel
> by looking at all virtual interfaces, so only mac80211 drivers which allow
> multiple channels (and non-mac80211 drivers) need to implement it.

Indeed, but I think mac80211 would be more appropriate than cfg80211
since the latter won't really have all the information unless it makes a
whole bunch of assumptions that we'll eventually have to reconsider.

johannes