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

[Brian Prodoehl <bprodoehl@gmail.com>]

On Fri, Jan 7, 2011 at 7:45 AM, Brian Prodoehl <bprodoehl@gmail.com> wrote:
> 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

Ah, I see.  All the driver changes I needed were because
ieee80211_channel_to_frequency() changed with the RFC patch, and this
patch keeps ieee80211_channel_to_frequency() the same.  Good stuff.