On Fri, Dec 24, 2010 at 7:44 AM, Bruno Randolf <br1@xxxxxxxxxxx> 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.
>
> Signed-off-by: Bruno Randolf <br1@xxxxxxxxxxx>
> ---
> -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);
You don't have to use them, but there are a few channel/frequency
conversion routines in include/ieee80211.h which could be reused in
these functions.
Regards,
Dave.
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