linux-kernel - Re: [PATCH wireless-next 1/3] wifi: cfg80211: Add utility API to get radio index from channel

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Message-ID: <37f00d636e1ffb68e383e0784b30e7e5cf48b4dd.camel@sipsolutions.net>
Date: Fri, 16 May 2025 09:51:39 +0200
From: Johannes Berg <johannes@...solutions.net>
To: Raj Kumar Bhagat <quic_rajkbhag@...cinc.com>
Cc: linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Vasanthakumar Thiagarajan <vasanthakumar.thiagarajan@....qualcomm.com>
Subject: Re: [PATCH wireless-next 1/3] wifi: cfg80211: Add utility API to
 get radio index from channel

On Wed, 2025-05-14 at 16:58 +0530, Raj Kumar Bhagat wrote:
> 
> +int cfg80211_get_radio_idx_by_chan(struct wiphy *wiphy,
> +				   const struct ieee80211_channel *chan)
> +{
> +	const struct wiphy_radio *radio;
> +	int i, j;
> +	u32 freq;
> +
> +	if (!chan)
> +		return -EINVAL;
> +
> +	freq = ieee80211_channel_to_khz(chan);
> +	for (i = 0; i < wiphy->n_radio; i++) {
> +		radio = &wiphy->radio[i];
> +		for (j = 0; j < radio->n_freq_range; j++) {
> +			if (freq >= radio->freq_range[j].start_freq &&
> +			    freq <= radio->freq_range[j].end_freq)
> +				return i;
> 

I believe we also discussed this in the past elsewhere, but I don't
think the the >= and <= can simultaneously be wrong. If the frequency
ranges for radios are adjacent, then the intervals here need to be half
open. I _think_ it should be < instead of <=, and therefore a half-open
interval of "[start, end[" (or "[start, end)" depending on your
preferred notation.)

johannes