Re: ath6kl_mgmt_tx with NULL chan

[Antonio Quartulli <antonio@open-mesh.com>]

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On Wed, Jun 05, 2013 at 02:57:07AM -0700, Kalle Valo wrote:
> Antonio Quartulli <ordex@autistici.org> writes:
> 
> > On Mon, Jun 03, 2013 at 05:04:08PM +0200, Nicolas Cavallari wrote:
> >> On 03/06/2013 16:59, Johannes Berg wrote:
> >> > On Mon, 2013-06-03 at 08:39 +0200, Antonio Quartulli wrote:
> >> >> From: Antonio Quartulli <antonio@open-mesh.com>
> >> >>
> >> >> Users may want to send a frame on the current channel
> >> >> without specifying it.
> >> >>
> >> >> Make mgmt_tx pass a NULL channel to mac80211 if none has
> >> >> been specified by the user.
> >> > 
> >> > cfg80211 isn't just a mac80211 frontend ... ;-)
> >> > 
> >> > Also, as Nicolas said, ath6kl_mgmt_tx() will crash after this patch if
> >> > it's called in AP mode w/o a channel, so you need to think about that.
> >> 
> >> It will crash unconditionally. All ath6kl_mgmt_tx()'s code paths access
> >> chan->center_freq at some point.
> >
> > Hello Nicolas,
> > I'm also CCing Kalle Valo since get_maintainer.pl told me he is the guy for
> > these kind of questions :-)
> >
> > I'm looking at ath6kl_mgmt_tx() in ath6kl/cfg80211.c and I've seen that the
> > currently "configured" frequency can be obtained by reading the
> > ath6kl_vif->ch_hint field.
> >
> > But, is this correct?
> 
> I did a quick look. To me using ch_hint looks correct.
> 
> > I couldn't see any real relation between the ch_hint field and the
> > real frequency (probably because a lot of logic is hidden to the
> > driver). I could only understand that the ch_hint field stores the
> > frequency passed as parameter during the connection, but I have found
> > no guarantee that this is the really used one.
> 
> Can you be more specific, please?
> 
> To me it looks that ch_hint is used both with ath6kl_wmi_reconnect_cmd()
> and ath6kl_wmi_connect_cmd() commands, which both are used to connect to
> a network. I don't see any other variables used for specifying the
> frequency to the firmware. But I could just be blind...

I agree with your analysis. My doubt came from the fact that I don't know what
the firmware does and I was wondering whether it could ignore the channel passed
as argument on connect for some reason.

Actually the doubt was raised due to the variable name "ch_HINT".
But you are the ath6k expert :-) Therefore I guess this can work.

Thanks a lot!

Cheers,

-- 
Antonio Quartulli

..each of us alone is worth nothing..
Ernesto "Che" Guevara

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