Re: [PATCH] cfg80211: Extend channel to frequency mapping for 802.11j

From: Dan Williams <dcbw@redhat.com>
To: Brian Prodoehl <bprodoehl@gmail.com>
Cc: Johannes Berg <johannes@sipsolutions.net>,
	Gertjan van Wingerde <gwingerde@gmail.com>,
	libertas-dev@lists.infradead.org, Bruno Randolf <br1@einfach.org>,
	Ivo van Doorn <IvDoorn@gmail.com>,
	linux-wireless@vger.kernel.org, linville@tuxdriver.com,
	users@rt2x00.serialmonkey.com
Subject: Re: [PATCH] cfg80211: Extend channel to frequency mapping for 802.11j
Date: Tue, 11 Jan 2011 09:09:35 -0600	[thread overview]
Message-ID: <1294758578.1808.1.camel@dcbw.foobar.com> (raw)
In-Reply-To: <AANLkTimg_udpa78Fbq+-48rOC38_jg_afaME=PYCsChr@mail.gmail.com>

On Tue, 2011-01-11 at 08:16 -0500, Brian Prodoehl wrote:
> On Tue, Jan 11, 2011 at 7:18 AM, Johannes Berg
> <johannes@sipsolutions.net> wrote:
> > On Tue, 2011-01-11 at 18:17 +0900, Bruno Randolf wrote:
> >
> >> > compat-wireless-2011-01-07.orig/drivers/net/wireless/libertas/cfg.c 2011-0
> >> > 1-07 15:03:59.000000000 -0500
> >> > +++
> >> > compat-wireless-2011-01-07/drivers/net/wireless/libertas/cfg.c      2011-01-08
> >> > 07:51:23.947290769 -0500
> >> > @@ -607,7 +607,8 @@
> >> >             /* No channel, no luck */
> >> >             if (chan_no != -1) {
> >> >                     struct wiphy *wiphy = priv->wdev->wiphy;
> >> > -                   int freq = ieee80211_channel_to_frequency(chan_no);
> >> > +                   int freq = ieee80211_channel_to_frequency(chan_no,
> >> > +                                   chan_no <= 14 ? IEEE80211_BAND_2GHZ :
> >> IEEE80211_BAND_5GHZ);
> >>
> >> The whole point of having the band argument is to avoid this. We now have
> >> overlapping channel numbers: channel 8 and 12 are defined in 5GHz as well as
> >> in 2.4GHz (that is for 20MHz channel width, there are more for 10 and 5MHz
> >> width, but we don't support that yet). The band has to come from the hardware
> >> or driver configuration.
> >
> > I don't think libertas (or orinoco) support the frequencies that
> > overlap, and they use the channel number in HW config, so it should be
> > fine.
> >
> > johannes
> 
> That's what it looked like to me, as well, for libertas.  For rt2x00,
> with it's dependence on binary firmwares from Ralink, extending the
> channel set seems very far from trivial.  Ralink advertises compliance
> with 802.11j (http://web.ralinktech.com/ralink/data/RT2800.pdf).  A
> year and a half ago I asked them directly what that compliance means
> (4.9GHz channels?  10MHz channel width?  misprint?) and didn't get a
> response.  A way to pull the band for rt2x00 didn't pop out at me, but
> if the maintainers have suggestions, that'll be great.  Also, if they
> have some idea what the level of 802.11j compliance is, I'd love to
> know!

While some libertas/fullmac devices do apparently support A, I haven't
seen any in person or heard of them in real use.  And the current
libertas driver certainly doesn't support 802.11a and wont, unless we
magically find a part that does.

Dan