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

[Brian Prodoehl <bprodoehl@gmail.com>]

On Fri, Jan 7, 2011 at 12:26 AM, Bruno Randolf <br1@einfach.org> wrote:
> Extend channel to frequency mapping for 802.11j Japan 4.9GHz band, according to
> IEEE802.11 section 17.3.8.3.2 and Annex J. Because there are now overlapping
> channel numbers in the 2GHz and 5GHz band we can't map from channel to
> frequency without knowing the band. This is no problem as in most contexts we
> know the band. In places where we don't know the band (and WEXT compatibility)
> we assume the 2GHz band for channels below 14.
>
> This patch does not implement all channel to frequency mappings defined in
> 802.11, it's just an extension for 802.11j 20MHz channels. 5MHz and 10MHz
> channels as well as 802.11y channels have been omitted.
>
> Signed-off-by: Bruno Randolf <br1@einfach.org>
> ---
>  include/net/cfg80211.h     |    3 ++-
>  net/mac80211/ibss.c        |    3 ++-
>  net/mac80211/mesh.c        |    2 +-
>  net/mac80211/mlme.c        |    8 +++++---
>  net/mac80211/scan.c        |    3 ++-
>  net/wireless/reg.c         |    6 +++---
>  net/wireless/util.c        |   36 ++++++++++++++++++++++--------------
>  net/wireless/wext-compat.c |    5 ++++-
>  8 files changed, 41 insertions(+), 25 deletions(-)
>
> diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
> index bcc9f44..cfaac36 100644
> --- a/include/net/cfg80211.h
> +++ b/include/net/cfg80211.h
> @@ -1788,8 +1788,9 @@ static inline void *wdev_priv(struct wireless_dev *wdev)
>  /**
>  * ieee80211_channel_to_frequency - convert channel number to frequency
>  * @chan: channel number
> + * @band: band, necessary due to channel number overlap
>  */
> -extern int ieee80211_channel_to_frequency(int chan);
> +extern int ieee80211_channel_to_frequency(int chan, enum ieee80211_band band);
>
>  /**
>  * ieee80211_frequency_to_channel - convert frequency to channel number
> diff --git a/net/mac80211/ibss.c b/net/mac80211/ibss.c
> index 53c7077..775fb63 100644
> --- a/net/mac80211/ibss.c
> +++ b/net/mac80211/ibss.c
> @@ -270,7 +270,8 @@ static void ieee80211_rx_bss_info(struct ieee80211_sub_if_data *sdata,
>        enum ieee80211_band band = rx_status->band;
>
>        if (elems->ds_params && elems->ds_params_len == 1)
> -               freq = ieee80211_channel_to_frequency(elems->ds_params[0]);
> +               freq = ieee80211_channel_to_frequency(elems->ds_params[0],
> +                                                     band);
>        else
>                freq = rx_status->freq;
>
> diff --git a/net/mac80211/mesh.c b/net/mac80211/mesh.c
> index ca3af46..1430cdc 100644
> --- a/net/mac80211/mesh.c
> +++ b/net/mac80211/mesh.c
> @@ -574,7 +574,7 @@ static void ieee80211_mesh_rx_bcn_presp(struct ieee80211_sub_if_data *sdata,
>                               &elems);
>
>        if (elems.ds_params && elems.ds_params_len == 1)
> -               freq = ieee80211_channel_to_frequency(elems.ds_params[0]);
> +               freq = ieee80211_channel_to_frequency(elems.ds_params[0], band);
>        else
>                freq = rx_status->freq;
>
> diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
> index 45fbb9e..33bd6d4 100644
> --- a/net/mac80211/mlme.c
> +++ b/net/mac80211/mlme.c
> @@ -176,7 +176,7 @@ static u32 ieee80211_enable_ht(struct ieee80211_sub_if_data *sdata,
>
>        /* check that channel matches the right operating channel */
>        if (local->hw.conf.channel->center_freq !=
> -           ieee80211_channel_to_frequency(hti->control_chan))
> +           ieee80211_channel_to_frequency(hti->control_chan, sband->band))
>                enable_ht = false;
>
>        if (enable_ht) {
> @@ -429,7 +429,8 @@ void ieee80211_sta_process_chanswitch(struct ieee80211_sub_if_data *sdata,
>                container_of((void *)bss, struct cfg80211_bss, priv);
>        struct ieee80211_channel *new_ch;
>        struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;
> -       int new_freq = ieee80211_channel_to_frequency(sw_elem->new_ch_num);
> +       int new_freq = ieee80211_channel_to_frequency(sw_elem->new_ch_num,
> +                                                     cbss->channel->band);
>
>        ASSERT_MGD_MTX(ifmgd);
>
> @@ -1519,7 +1520,8 @@ static void ieee80211_rx_bss_info(struct ieee80211_sub_if_data *sdata,
>        }
>
>        if (elems->ds_params && elems->ds_params_len == 1)
> -               freq = ieee80211_channel_to_frequency(elems->ds_params[0]);
> +               freq = ieee80211_channel_to_frequency(elems->ds_params[0],
> +                                                     rx_status->band);
>        else
>                freq = rx_status->freq;
>
> diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
> index fb274db..1ef73be 100644
> --- a/net/mac80211/scan.c
> +++ b/net/mac80211/scan.c
> @@ -196,7 +196,8 @@ ieee80211_scan_rx(struct ieee80211_sub_if_data *sdata, struct sk_buff *skb)
>        ieee802_11_parse_elems(elements, skb->len - baselen, &elems);
>
>        if (elems.ds_params && elems.ds_params_len == 1)
> -               freq = ieee80211_channel_to_frequency(elems.ds_params[0]);
> +               freq = ieee80211_channel_to_frequency(elems.ds_params[0],
> +                                                     rx_status->band);
>        else
>                freq = rx_status->freq;
>
> diff --git a/net/wireless/reg.c b/net/wireless/reg.c
> index 37693b6..c565689 100644
> --- a/net/wireless/reg.c
> +++ b/net/wireless/reg.c
> @@ -1801,9 +1801,9 @@ void regulatory_hint_disconnect(void)
>
>  static bool freq_is_chan_12_13_14(u16 freq)
>  {
> -       if (freq == ieee80211_channel_to_frequency(12) ||
> -           freq == ieee80211_channel_to_frequency(13) ||
> -           freq == ieee80211_channel_to_frequency(14))
> +       if (freq == ieee80211_channel_to_frequency(12, IEEE80211_BAND_2GHZ) ||
> +           freq == ieee80211_channel_to_frequency(13, IEEE80211_BAND_2GHZ) ||
> +           freq == ieee80211_channel_to_frequency(14, IEEE80211_BAND_2GHZ))
>                return true;
>        return false;
>  }
> diff --git a/net/wireless/util.c b/net/wireless/util.c
> index 7620ae2..4ed065d 100644
> --- a/net/wireless/util.c
> +++ b/net/wireless/util.c
> @@ -29,29 +29,37 @@ ieee80211_get_response_rate(struct ieee80211_supported_band *sband,
>  }
>  EXPORT_SYMBOL(ieee80211_get_response_rate);
>
> -int ieee80211_channel_to_frequency(int chan)
> +int ieee80211_channel_to_frequency(int chan, enum ieee80211_band band)
>  {
> -       if (chan < 14)
> -               return 2407 + chan * 5;
> -
> -       if (chan == 14)
> -               return 2484;
> -
> -       /* FIXME: 802.11j 17.3.8.3.2 */
> -       return (chan + 1000) * 5;
> +       /* see 802.11 17.3.8.3.2 and Annex J
> +        * there are overlapping channel numbers in 5GHz and 2GHz bands */
> +       if (band == IEEE80211_BAND_5GHZ) {
> +               if (chan >= 182 && chan <= 196)
> +                       return 4000 + chan * 5;
> +               else
> +                       return 5000 + chan * 5;
> +       } else { /* IEEE80211_BAND_2GHZ */
> +               if (chan == 14)
> +                       return 2484;
> +               else if (chan < 14)
> +                       return 2407 + chan * 5;
> +               else
> +                       return 0; /* not supported */
> +       }
>  }
>  EXPORT_SYMBOL(ieee80211_channel_to_frequency);
>
>  int ieee80211_frequency_to_channel(int freq)
>  {
> +       /* see 802.11 17.3.8.3.2 and Annex J */
>        if (freq == 2484)
>                return 14;
> -
> -       if (freq < 2484)
> +       else if (freq < 2484)
>                return (freq - 2407) / 5;
> -
> -       /* FIXME: 802.11j 17.3.8.3.2 */
> -       return freq/5 - 1000;
> +       else if (freq >= 4910 && freq <= 4980)
> +               return (freq - 4000) / 5;
> +       else
> +               return (freq - 5000) / 5;
>  }
>  EXPORT_SYMBOL(ieee80211_frequency_to_channel);
>
> diff --git a/net/wireless/wext-compat.c b/net/wireless/wext-compat.c
> index 3e5dbd4..7f1f4ec 100644
> --- a/net/wireless/wext-compat.c
> +++ b/net/wireless/wext-compat.c
> @@ -267,9 +267,12 @@ int cfg80211_wext_freq(struct wiphy *wiphy, struct iw_freq *freq)
>         * -EINVAL for impossible things.
>         */
>        if (freq->e == 0) {
> +               enum ieee80211_band band = IEEE80211_BAND_2GHZ;
>                if (freq->m < 0)
>                        return 0;
> -               return ieee80211_channel_to_frequency(freq->m);
> +               if (freq->m > 14)
> +                       band = IEEE80211_BAND_5GHZ;
> +               return ieee80211_channel_to_frequency(freq->m, band);
>        } else {
>                int i, div = 1000000;
>                for (i = 0; i < freq->e; i++)


Do all drivers still build with this patch?  I applied the previous
RFC version of this patch to a late-December cut of compat-wireless,
and had to touch the receive-handling code in a half-dozen or so
drivers due to the API changes.

-Brian