net/wireless/chan.c

/*
 * This file contains helper code to handle channel
 * settings and keeping track of what is possible at
 * any point in time.
 *
 * Copyright 2009	Johannes Berg <johannes@sipsolutions.net>
 */

#include <linux/export.h>
#include <net/cfg80211.h>
#include "core.h"
#include "rdev-ops.h"

void cfg80211_chandef_create(struct cfg80211_chan_def *chandef,
			     struct ieee80211_channel *chan,
			     enum nl80211_channel_type chan_type)
{
	if (WARN_ON(!chan))
		return;

	chandef->chan = chan;
	chandef->center_freq2 = 0;

	switch (chan_type) {
	case NL80211_CHAN_NO_HT:
		chandef->width = NL80211_CHAN_WIDTH_20_NOHT;
		chandef->center_freq1 = chan->center_freq;
		break;
	case NL80211_CHAN_HT20:
		chandef->width = NL80211_CHAN_WIDTH_20;
		chandef->center_freq1 = chan->center_freq;
		break;
	case NL80211_CHAN_HT40PLUS:
		chandef->width = NL80211_CHAN_WIDTH_40;
		chandef->center_freq1 = chan->center_freq + 10;
		break;
	case NL80211_CHAN_HT40MINUS:
		chandef->width = NL80211_CHAN_WIDTH_40;
		chandef->center_freq1 = chan->center_freq - 10;
		break;
	default:
		WARN_ON(1);
	}
}
EXPORT_SYMBOL(cfg80211_chandef_create);

bool cfg80211_chandef_valid(const struct cfg80211_chan_def *chandef)
{
	u32 control_freq;

	if (!chandef->chan)
		return false;

	control_freq = chandef->chan->center_freq;

	switch (chandef->width) {
	case NL80211_CHAN_WIDTH_5:
	case NL80211_CHAN_WIDTH_10:
	case NL80211_CHAN_WIDTH_20:
	case NL80211_CHAN_WIDTH_20_NOHT:
		if (chandef->center_freq1 != control_freq)
			return false;
		if (chandef->center_freq2)
			return false;
		break;
	case NL80211_CHAN_WIDTH_40:
		if (chandef->center_freq1 != control_freq + 10 &&
		    chandef->center_freq1 != control_freq - 10)
			return false;
		if (chandef->center_freq2)
			return false;
		break;
	case NL80211_CHAN_WIDTH_80P80:
		if (chandef->center_freq1 != control_freq + 30 &&
		    chandef->center_freq1 != control_freq + 10 &&
		    chandef->center_freq1 != control_freq - 10 &&
		    chandef->center_freq1 != control_freq - 30)
			return false;
		if (!chandef->center_freq2)
			return false;
		/* adjacent is not allowed -- that's a 160 MHz channel */
		if (chandef->center_freq1 - chandef->center_freq2 == 80 ||
		    chandef->center_freq2 - chandef->center_freq1 == 80)
			return false;
		break;
	case NL80211_CHAN_WIDTH_80:
		if (chandef->center_freq1 != control_freq + 30 &&
		    chandef->center_freq1 != control_freq + 10 &&
		    chandef->center_freq1 != control_freq - 10 &&
		    chandef->center_freq1 != control_freq - 30)
			return false;
		if (chandef->center_freq2)
			return false;
		break;
	case NL80211_CHAN_WIDTH_160:
		if (chandef->center_freq1 != control_freq + 70 &&
		    chandef->center_freq1 != control_freq + 50 &&
		    chandef->center_freq1 != control_freq + 30 &&
		    chandef->center_freq1 != control_freq + 10 &&
		    chandef->center_freq1 != control_freq - 10 &&
		    chandef->center_freq1 != control_freq - 30 &&
		    chandef->center_freq1 != control_freq - 50 &&
		    chandef->center_freq1 != control_freq - 70)
			return false;
		if (chandef->center_freq2)
			return false;
		break;
	default:
		return false;
	}

	return true;
}
EXPORT_SYMBOL(cfg80211_chandef_valid);

static void chandef_primary_freqs(const struct cfg80211_chan_def *c,
				  int *pri40, int *pri80)
{
	int tmp;

	switch (c->width) {
	case NL80211_CHAN_WIDTH_40:
		*pri40 = c->center_freq1;
		*pri80 = 0;
		break;
	case NL80211_CHAN_WIDTH_80:
	case NL80211_CHAN_WIDTH_80P80:
		*pri80 = c->center_freq1;
		/* n_P20 */
		tmp = (30 + c->chan->center_freq - c->center_freq1)/20;
		/* n_P40 */
		tmp /= 2;
		/* freq_P40 */
		*pri40 = c->center_freq1 - 20 + 40 * tmp;
		break;
	case NL80211_CHAN_WIDTH_160:
		/* n_P20 */
		tmp = (70 + c->chan->center_freq - c->center_freq1)/20;
		/* n_P40 */
		tmp /= 2;
		/* freq_P40 */
		*pri40 = c->center_freq1 - 60 + 40 * tmp;
		/* n_P80 */
		tmp /= 2;
		*pri80 = c->center_freq1 - 40 + 80 * tmp;
		break;
	default:
		WARN_ON_ONCE(1);
	}
}

static int cfg80211_chandef_get_width(const struct cfg80211_chan_def *c)
{
	int width;

	switch (c->width) {
	case NL80211_CHAN_WIDTH_5:
		width = 5;
		break;
	case NL80211_CHAN_WIDTH_10:
		width = 10;
		break;
	case NL80211_CHAN_WIDTH_20:
	case NL80211_CHAN_WIDTH_20_NOHT:
		width = 20;
		break;
	case NL80211_CHAN_WIDTH_40:
		width = 40;
		break;
	case NL80211_CHAN_WIDTH_80P80:
	case NL80211_CHAN_WIDTH_80:
		width = 80;
		break;
	case NL80211_CHAN_WIDTH_160:
		width = 160;
		break;
	default:
		WARN_ON_ONCE(1);
		return -1;
	}
	return width;
}

const struct cfg80211_chan_def *
cfg80211_chandef_compatible(const struct cfg80211_chan_def *c1,
			    const struct cfg80211_chan_def *c2)
{
	u32 c1_pri40, c1_pri80, c2_pri40, c2_pri80;

	/* If they are identical, return */
	if (cfg80211_chandef_identical(c1, c2))
		return c1;

	/* otherwise, must have same control channel */
	if (c1->chan != c2->chan)
		return NULL;

	/*
	 * If they have the same width, but aren't identical,
	 * then they can't be compatible.
	 */
	if (c1->width == c2->width)
		return NULL;

	/*
	 * can't be compatible if one of them is 5 or 10 MHz,
	 * but they don't have the same width.
	 */
	if (c1->width == NL80211_CHAN_WIDTH_5 ||
	    c1->width == NL80211_CHAN_WIDTH_10 ||
	    c2->width == NL80211_CHAN_WIDTH_5 ||
	    c2->width == NL80211_CHAN_WIDTH_10)
		return NULL;

	if (c1->width == NL80211_CHAN_WIDTH_20_NOHT ||
	    c1->width == NL80211_CHAN_WIDTH_20)
		return c2;

	if (c2->width == NL80211_CHAN_WIDTH_20_NOHT ||
	    c2->width == NL80211_CHAN_WIDTH_20)
		return c1;

	chandef_primary_freqs(c1, &c1_pri40, &c1_pri80);
	chandef_primary_freqs(c2, &c2_pri40, &c2_pri80);

	if (c1_pri40 != c2_pri40)
		return NULL;

	WARN_ON(!c1_pri80 && !c2_pri80);
	if (c1_pri80 && c2_pri80 && c1_pri80 != c2_pri80)
		return NULL;

	if (c1->width > c2->width)
		return c1;
	return c2;
}
EXPORT_SYMBOL(cfg80211_chandef_compatible);

static void cfg80211_set_chans_dfs_state(struct wiphy *wiphy, u32 center_freq,
					 u32 bandwidth,
					 enum nl80211_dfs_state dfs_state)
{
	struct ieee80211_channel *c;
	u32 freq;

	for (freq = center_freq - bandwidth/2 + 10;
	     freq <= center_freq + bandwidth/2 - 10;
	     freq += 20) {
		c = ieee80211_get_channel(wiphy, freq);
		if (!c || !(c->flags & IEEE80211_CHAN_RADAR))
			continue;

		c->dfs_state = dfs_state;
		c->dfs_state_entered = jiffies;
	}
}

void cfg80211_set_dfs_state(struct wiphy *wiphy,
			    const struct cfg80211_chan_def *chandef,
			    enum nl80211_dfs_state dfs_state)
{
	int width;

	if (WARN_ON(!cfg80211_chandef_valid(chandef)))
		return;

	width = cfg80211_chandef_get_width(chandef);
	if (width < 0)
		return;

	cfg80211_set_chans_dfs_state(wiphy, chandef->center_freq1,
				     width, dfs_state);

	if (!chandef->center_freq2)
		return;
	cfg80211_set_chans_dfs_state(wiphy, chandef->center_freq2,
				     width, dfs_state);
}

static u32 cfg80211_get_start_freq(u32 center_freq,
				   u32 bandwidth)
{
	u32 start_freq;

	if (bandwidth <= 20)
		start_freq = center_freq;
	else
		start_freq = center_freq - bandwidth/2 + 10;

	return start_freq;
}

static u32 cfg80211_get_end_freq(u32 center_freq,
				 u32 bandwidth)
{
	u32 end_freq;

	if (bandwidth <= 20)
		end_freq = center_freq;
	else
		end_freq = center_freq + bandwidth/2 - 10;

	return end_freq;
}

static int cfg80211_get_chans_dfs_required(struct wiphy *wiphy,
					    u32 center_freq,
					    u32 bandwidth)
{
	struct ieee80211_channel *c;
	u32 freq, start_freq, end_freq;

	start_freq = cfg80211_get_start_freq(center_freq, bandwidth);
	end_freq = cfg80211_get_end_freq(center_freq, bandwidth);

	for (freq = start_freq; freq <= end_freq; freq += 20) {
		c = ieee80211_get_channel(wiphy, freq);
		if (!c)
			return -EINVAL;

		if (c->flags & IEEE80211_CHAN_RADAR)
			return 1;
	}
	return 0;
}


int cfg80211_chandef_dfs_required(struct wiphy *wiphy,
				  const struct cfg80211_chan_def *chandef)
{
	int width;
	int r;

	if (WARN_ON(!cfg80211_chandef_valid(chandef)))
		return -EINVAL;

	width = cfg80211_chandef_get_width(chandef);
	if (width < 0)
		return -EINVAL;

	r = cfg80211_get_chans_dfs_required(wiphy, chandef->center_freq1,
					    width);
	if (r)
		return r;

	if (!chandef->center_freq2)
		return 0;

	return cfg80211_get_chans_dfs_required(wiphy, chandef->center_freq2,
					       width);
}
EXPORT_SYMBOL(cfg80211_chandef_dfs_required);

static int cfg80211_get_chans_dfs_usable(struct wiphy *wiphy,
					 u32 center_freq,
					 u32 bandwidth)
{
	struct ieee80211_channel *c;
	u32 freq, start_freq, end_freq;
	int count = 0;

	start_freq = cfg80211_get_start_freq(center_freq, bandwidth);
	end_freq = cfg80211_get_end_freq(center_freq, bandwidth);

	/*
	 * Check entire range of channels for the bandwidth.
	 * Check all channels are DFS channels (DFS_USABLE or
	 * DFS_AVAILABLE). Return number of usable channels
	 * (require CAC). Allow DFS and non-DFS channel mix.
	 */
	for (freq = start_freq; freq <= end_freq; freq += 20) {
		c = ieee80211_get_channel(wiphy, freq);
		if (!c)
			return -EINVAL;

		if (c->flags & IEEE80211_CHAN_DISABLED)
			return -EINVAL;

		if (c->flags & IEEE80211_CHAN_RADAR) {
			if (c->dfs_state == NL80211_DFS_UNAVAILABLE)
				return -EINVAL;

			if (c->dfs_state == NL80211_DFS_USABLE)
				count++;
		}
	}

	return count;
}

bool cfg80211_chandef_dfs_usable(struct wiphy *wiphy,
				 const struct cfg80211_chan_def *chandef)
{
	int width;
	int r1, r2 = 0;

	if (WARN_ON(!cfg80211_chandef_valid(chandef)))
		return false;

	width = cfg80211_chandef_get_width(chandef);
	if (width < 0)
		return false;

	r1 = cfg80211_get_chans_dfs_usable(wiphy, chandef->center_freq1,
					  width);

	if (r1 < 0)
		return false;

	switch (chandef->width) {
	case NL80211_CHAN_WIDTH_80P80:
		WARN_ON(!chandef->center_freq2);
		r2 = cfg80211_get_chans_dfs_usable(wiphy,
						   chandef->center_freq2,
						   width);
		if (r2 < 0)
			return false;
		break;
	default:
		WARN_ON(chandef->center_freq2);
		break;
	}

	return (r1 + r2 > 0);
}


static bool cfg80211_get_chans_dfs_available(struct wiphy *wiphy,
					     u32 center_freq,
					     u32 bandwidth)
{
	struct ieee80211_channel *c;
	u32 freq, start_freq, end_freq;

	start_freq = cfg80211_get_start_freq(center_freq, bandwidth);
	end_freq = cfg80211_get_end_freq(center_freq, bandwidth);

	/*
	 * Check entire range of channels for the bandwidth.
	 * If any channel in between is disabled or has not
	 * had gone through CAC return false
	 */
	for (freq = start_freq; freq <= end_freq; freq += 20) {
		c = ieee80211_get_channel(wiphy, freq);
		if (!c)
			return false;

		if (c->flags & IEEE80211_CHAN_DISABLED)
			return false;

		if ((c->flags & IEEE80211_CHAN_RADAR)  &&
		    (c->dfs_state != NL80211_DFS_AVAILABLE))
			return false;
	}

	return true;
}

static bool cfg80211_chandef_dfs_available(struct wiphy *wiphy,
				const struct cfg80211_chan_def *chandef)
{
	int width;
	int r;

	if (WARN_ON(!cfg80211_chandef_valid(chandef)))
		return false;

	width = cfg80211_chandef_get_width(chandef);
	if (width < 0)
		return false;

	r = cfg80211_get_chans_dfs_available(wiphy, chandef->center_freq1,
					     width);

	/* If any of channels unavailable for cf1 just return */
	if (!r)
		return r;

	switch (chandef->width) {
	case NL80211_CHAN_WIDTH_80P80:
		WARN_ON(!chandef->center_freq2);
		r = cfg80211_get_chans_dfs_available(wiphy,
						     chandef->center_freq2,
						     width);
	default:
		WARN_ON(chandef->center_freq2);
		break;
	}

	return r;
}

static unsigned int cfg80211_get_chans_dfs_cac_time(struct wiphy *wiphy,
						    u32 center_freq,
						    u32 bandwidth)
{
	struct ieee80211_channel *c;
	u32 start_freq, end_freq, freq;
	unsigned int dfs_cac_ms = 0;

	start_freq = cfg80211_get_start_freq(center_freq, bandwidth);
	end_freq = cfg80211_get_end_freq(center_freq, bandwidth);

	for (freq = start_freq; freq <= end_freq; freq += 20) {
		c = ieee80211_get_channel(wiphy, freq);
		if (!c)
			return 0;

		if (c->flags & IEEE80211_CHAN_DISABLED)
			return 0;

		if (!(c->flags & IEEE80211_CHAN_RADAR))
			continue;

		if (c->dfs_cac_ms > dfs_cac_ms)
			dfs_cac_ms = c->dfs_cac_ms;
	}

	return dfs_cac_ms;
}

unsigned int
cfg80211_chandef_dfs_cac_time(struct wiphy *wiphy,
			      const struct cfg80211_chan_def *chandef)
{
	int width;
	unsigned int t1 = 0, t2 = 0;

	if (WARN_ON(!cfg80211_chandef_valid(chandef)))
		return 0;

	width = cfg80211_chandef_get_width(chandef);
	if (width < 0)
		return 0;

	t1 = cfg80211_get_chans_dfs_cac_time(wiphy,
					     chandef->center_freq1,
					     width);

	if (!chandef->center_freq2)
		return t1;

	t2 = cfg80211_get_chans_dfs_cac_time(wiphy,
					     chandef->center_freq2,
					     width);

	return max(t1, t2);
}

static bool cfg80211_secondary_chans_ok(struct wiphy *wiphy,
					u32 center_freq, u32 bandwidth,
					u32 prohibited_flags)
{
	struct ieee80211_channel *c;
	u32 freq, start_freq, end_freq;

	start_freq = cfg80211_get_start_freq(center_freq, bandwidth);
	end_freq = cfg80211_get_end_freq(center_freq, bandwidth);

	for (freq = start_freq; freq <= end_freq; freq += 20) {
		c = ieee80211_get_channel(wiphy, freq);
		if (!c || c->flags & prohibited_flags)
			return false;
	}

	return true;
}

bool cfg80211_chandef_usable(struct wiphy *wiphy,
			     const struct cfg80211_chan_def *chandef,
			     u32 prohibited_flags)
{
	struct ieee80211_sta_ht_cap *ht_cap;
	struct ieee80211_sta_vht_cap *vht_cap;
	u32 width, control_freq;

	if (WARN_ON(!cfg80211_chandef_valid(chandef)))
		return false;

	ht_cap = &wiphy->bands[chandef->chan->band]->ht_cap;
	vht_cap = &wiphy->bands[chandef->chan->band]->vht_cap;

	control_freq = chandef->chan->center_freq;

	switch (chandef->width) {
	case NL80211_CHAN_WIDTH_5:
		width = 5;
		break;
	case NL80211_CHAN_WIDTH_10:
		width = 10;
		break;
	case NL80211_CHAN_WIDTH_20:
		if (!ht_cap->ht_supported)
			return false;
	case NL80211_CHAN_WIDTH_20_NOHT:
		width = 20;
		break;
	case NL80211_CHAN_WIDTH_40:
		width = 40;
		if (!ht_cap->ht_supported)
			return false;
		if (!(ht_cap->cap & IEEE80211_HT_CAP_SUP_WIDTH_20_40) ||
		    ht_cap->cap & IEEE80211_HT_CAP_40MHZ_INTOLERANT)
			return false;
		if (chandef->center_freq1 < control_freq &&
		    chandef->chan->flags & IEEE80211_CHAN_NO_HT40MINUS)
			return false;
		if (chandef->center_freq1 > control_freq &&
		    chandef->chan->flags & IEEE80211_CHAN_NO_HT40PLUS)
			return false;
		break;
	case NL80211_CHAN_WIDTH_80P80:
		if (!(vht_cap->cap & IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_160_80PLUS80MHZ))
			return false;
	case NL80211_CHAN_WIDTH_80:
		if (!vht_cap->vht_supported)
			return false;
		prohibited_flags |= IEEE80211_CHAN_NO_80MHZ;
		width = 80;
		break;
	case NL80211_CHAN_WIDTH_160:
		if (!vht_cap->vht_supported)
			return false;
		if (!(vht_cap->cap & IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_160MHZ))
			return false;
		prohibited_flags |= IEEE80211_CHAN_NO_160MHZ;
		width = 160;
		break;
	default:
		WARN_ON_ONCE(1);
		return false;
	}

	/*
	 * TODO: What if there are only certain 80/160/80+80 MHz channels
	 *	 allowed by the driver, or only certain combinations?
	 *	 For 40 MHz the driver can set the NO_HT40 flags, but for
	 *	 80/160 MHz and in particular 80+80 MHz this isn't really
	 *	 feasible and we only have NO_80MHZ/NO_160MHZ so far but
	 *	 no way to cover 80+80 MHz or more complex restrictions.
	 *	 Note that such restrictions also need to be advertised to
	 *	 userspace, for example for P2P channel selection.
	 */

	if (width > 20)
		prohibited_flags |= IEEE80211_CHAN_NO_OFDM;

	/* 5 and 10 MHz are only defined for the OFDM PHY */
	if (width < 20)
		prohibited_flags |= IEEE80211_CHAN_NO_OFDM;


	if (!cfg80211_secondary_chans_ok(wiphy, chandef->center_freq1,
					 width, prohibited_flags))
		return false;

	if (!chandef->center_freq2)
		return true;
	return cfg80211_secondary_chans_ok(wiphy, chandef->center_freq2,
					   width, prohibited_flags);
}
EXPORT_SYMBOL(cfg80211_chandef_usable);

/*
 * For GO only, check if the channel can be used under permissive conditions
 * mandated by the some regulatory bodies, i.e., the channel is marked with
 * IEEE80211_CHAN_GO_CONCURRENT and there is an additional station interface
 * associated to an AP on the same channel or on the same UNII band
 * (assuming that the AP is an authorized master).
 * In addition allow the GO to operate on a channel on which indoor operation is
 * allowed, iff we are currently operating in an indoor environment.
 */
static bool cfg80211_go_permissive_chan(struct cfg80211_registered_device *rdev,
					struct ieee80211_channel *chan)
{
	struct wireless_dev *wdev_iter;
	struct wiphy *wiphy = wiphy_idx_to_wiphy(rdev->wiphy_idx);

	ASSERT_RTNL();

	if (!config_enabled(CONFIG_CFG80211_REG_RELAX_NO_IR) ||
	    !(wiphy->regulatory_flags & REGULATORY_ENABLE_RELAX_NO_IR))
		return false;

	if (regulatory_indoor_allowed() &&
	    (chan->flags & IEEE80211_CHAN_INDOOR_ONLY))
		return true;

	if (!(chan->flags & IEEE80211_CHAN_GO_CONCURRENT))
		return false;

	/*
	 * Generally, it is possible to rely on another device/driver to allow
	 * the GO concurrent relaxation, however, since the device can further
	 * enforce the relaxation (by doing a similar verifications as this),
	 * and thus fail the GO instantiation, consider only the interfaces of
	 * the current registered device.
	 */
	list_for_each_entry(wdev_iter, &rdev->wdev_list, list) {
		struct ieee80211_channel *other_chan = NULL;
		int r1, r2;

		if (wdev_iter->iftype != NL80211_IFTYPE_STATION ||
		    !netif_running(wdev_iter->netdev))
			continue;

		wdev_lock(wdev_iter);
		if (wdev_iter->current_bss)
			other_chan = wdev_iter->current_bss->pub.channel;
		wdev_unlock(wdev_iter);

		if (!other_chan)
			continue;

		if (chan == other_chan)
			return true;

		if (chan->band != IEEE80211_BAND_5GHZ)
			continue;

		r1 = cfg80211_get_unii(chan->center_freq);
		r2 = cfg80211_get_unii(other_chan->center_freq);

		if (r1 != -EINVAL && r1 == r2)
			return true;
	}

	return false;
}

bool cfg80211_reg_can_beacon(struct wiphy *wiphy,
			     struct cfg80211_chan_def *chandef,
			     enum nl80211_iftype iftype)
{
	struct cfg80211_registered_device *rdev = wiphy_to_dev(wiphy);
	bool res;
	u32 prohibited_flags = IEEE80211_CHAN_DISABLED |
			       IEEE80211_CHAN_RADAR;

	trace_cfg80211_reg_can_beacon(wiphy, chandef, iftype);

	/*
	 * Under certain conditions suggested by the some regulatory bodies
	 * a GO can operate on channels marked with IEEE80211_NO_IR
	 * so set this flag only if such relaxations are not enabled and
	 * the conditions are not met.
	 */
	if (iftype != NL80211_IFTYPE_P2P_GO ||
	    !cfg80211_go_permissive_chan(rdev, chandef->chan))
		prohibited_flags |= IEEE80211_CHAN_NO_IR;

	if (cfg80211_chandef_dfs_required(wiphy, chandef) > 0 &&
	    cfg80211_chandef_dfs_available(wiphy, chandef)) {
		/* We can skip IEEE80211_CHAN_NO_IR if chandef dfs available */
		prohibited_flags = IEEE80211_CHAN_DISABLED;
	}

	res = cfg80211_chandef_usable(wiphy, chandef, prohibited_flags);

	trace_cfg80211_return_bool(res);
	return res;
}
EXPORT_SYMBOL(cfg80211_reg_can_beacon);

int cfg80211_set_monitor_channel(struct cfg80211_registered_device *rdev,
				 struct cfg80211_chan_def *chandef)
{
	if (!rdev->ops->set_monitor_channel)
		return -EOPNOTSUPP;
	if (!cfg80211_has_monitors_only(rdev))
		return -EBUSY;

	return rdev_set_monitor_channel(rdev, chandef);
}

void
cfg80211_get_chan_state(struct wireless_dev *wdev,
		        struct ieee80211_channel **chan,
		        enum cfg80211_chan_mode *chanmode,
		        u8 *radar_detect)
{
	*chan = NULL;
	*chanmode = CHAN_MODE_UNDEFINED;

	ASSERT_WDEV_LOCK(wdev);

	if (wdev->netdev && !netif_running(wdev->netdev))
		return;

	switch (wdev->iftype) {
	case NL80211_IFTYPE_ADHOC:
		if (wdev->current_bss) {
			*chan = wdev->current_bss->pub.channel;
			*chanmode = (wdev->ibss_fixed &&
				     !wdev->ibss_dfs_possible)
				  ? CHAN_MODE_SHARED
				  : CHAN_MODE_EXCLUSIVE;

			/* consider worst-case - IBSS can try to return to the
			 * original user-specified channel as creator */
			if (wdev->ibss_dfs_possible)
				*radar_detect |= BIT(wdev->chandef.width);
			return;
		}
		break;
	case NL80211_IFTYPE_STATION:
	case NL80211_IFTYPE_P2P_CLIENT:
		if (wdev->current_bss) {
			*chan = wdev->current_bss->pub.channel;
			*chanmode = CHAN_MODE_SHARED;
			return;
		}
		break;
	case NL80211_IFTYPE_AP:
	case NL80211_IFTYPE_P2P_GO:
		if (wdev->cac_started) {
			*chan = wdev->chandef.chan;
			*chanmode = CHAN_MODE_SHARED;
			*radar_detect |= BIT(wdev->chandef.width);
		} else if (wdev->beacon_interval) {
			*chan = wdev->chandef.chan;
			*chanmode = CHAN_MODE_SHARED;

			if (cfg80211_chandef_dfs_required(wdev->wiphy,
							  &wdev->chandef))
				*radar_detect |= BIT(wdev->chandef.width);
		}
		return;
	case NL80211_IFTYPE_MESH_POINT:
		if (wdev->mesh_id_len) {
			*chan = wdev->chandef.chan;
			*chanmode = CHAN_MODE_SHARED;

			if (cfg80211_chandef_dfs_required(wdev->wiphy,
							  &wdev->chandef))
				*radar_detect |= BIT(wdev->chandef.width);
		}
		return;
	case NL80211_IFTYPE_MONITOR:
	case NL80211_IFTYPE_AP_VLAN:
	case NL80211_IFTYPE_WDS:
	case NL80211_IFTYPE_P2P_DEVICE:
		/* these interface types don't really have a channel */
		return;
	case NL80211_IFTYPE_UNSPECIFIED:
	case NUM_NL80211_IFTYPES:
		WARN_ON(1);
	}
}