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Subject: Re: [PATCH] cfg80211: Add new helper function for channels
To:     Amar Singhal <asinghal@codeaurora.org>, jouni@codeaurora.org
Cc:     johannes@sipsolutions.net, linux-wireless@vger.kernel.org,
        jjohnson@codeaurora.org, rmanohar@codeaurora.org
References: <1567115381-7831-1-git-send-email-asinghal@codeaurora.org>
From:   Arend Van Spriel <arend.vanspriel@broadcom.com>
Message-ID: <01082dca-8d71-c674-1f61-ab5d7e07c007@broadcom.com>
Date:   Fri, 30 Aug 2019 12:40:19 +0200
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On 8/29/2019 11:49 PM, Amar Singhal wrote:
> Add new helper function to convert (chan_number, oper_class) pair to
> frequency. Call this function ieee80211_channel_op_class_to_frequency.
> This function would be very useful in the context of 6 GHz channels,
> where channel number is not unique.

That 'unique' statement does not apply to 6GHz by itself. The addition 
of 6GHz channels makes channel numbers across bands not unique.

The funcion
> Signed-off-by: Amar Singhal <asinghal@codeaurora.org>
> ---
>   include/net/cfg80211.h | 10 ++++++++++
>   net/wireless/util.c    | 23 +++++++++++++++++++++++
>   2 files changed, 33 insertions(+)
> 
> diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
> index 6467b60..decafba 100644
> --- a/include/net/cfg80211.h
> +++ b/include/net/cfg80211.h
> @@ -4914,1 +4914,1 @@ static inline void *wdev_priv(struct wireless_dev *wdev)
>   int ieee80211_channel_to_frequency(int chan, enum nl80211_band band);
> 
>   /**
> + * ieee80211_channel_op_class_to_frequency - convert
> + * (channel, operating class) to frequency
> + * @chan_num: channel number
> + * @global_op_class: global operating class
> + *
> + * Return: The corresponding frequency, or 0 if the conversion failed.
> + */
> +int ieee80211_channel_op_class_to_frequency(u8 chan_num, u8 global_op_class);
> +
> +/**
>    * ieee80211_frequency_to_channel - convert frequency to channel number
>    * @freq: center frequency
>    * Return: The corresponding channel, or 0 if the conversion failed.
> diff --git a/net/wireless/util.c b/net/wireless/util.c
> index 9aba8d54..7f64b4a 100644
> --- a/net/wireless/util.c
> +++ b/net/wireless/util.c
> @@ -144,6 +144,29 @@ struct ieee80211_channel *ieee80211_get_channel(struct wiphy *wiphy, int freq)
>   }
>   EXPORT_SYMBOL(ieee80211_get_channel);
> 
> +int ieee80211_channel_op_class_to_frequency(u8 chan_num, u8 global_op_class)
> +{
> +	if (global_op_class >= 131 && global_op_class <= 135)
> +		return (5940 + 5 * chan_num);
> +	else if (global_op_class >= 115 && global_op_class <= 130)
> +		return (5000 + 5 * chan_num);
> +	else if (global_op_class >= 112 && global_op_class <= 113)
> +		return (5000 + 5 * chan_num);
> +	else if (global_op_class >= 109 && global_op_class <= 110)
> +		return (4000 + 5 * chan_num);
> +	else if (global_op_class >= 83 && global_op_class <= 84)
> +		return (2407 + 5 * chan_num);
> +	else if (global_op_class == 81)
> +		return (2407 + 5 * chan_num);
> +	else if (global_op_class == 82)
> +		return (2414 + 5 * chan_num);
> +	else if (global_op_class == 180)
> +		return (56160 + 5 * chan_num);
> +	else
> +		return 0;
> +}
> +EXPORT_SYMBOL(ieee80211_channel_op_class_to_frequency);

The function ieee80211_operating_class_to_band() uses ranges within 
switch statement, eg.:

         case 128 ... 130:
                 *band = NL80211_BAND_5GHZ;
                 return true;

For consistency it might be good to do the same here.

Regards,
Arend