From: Ondrej Jirman <megi@xff.cz>

Internally wiphy writes to individual channels in this structure,
so we must not share one static definition of channel list between
multiple device instances, because that causes hard to debug
breakage.

For example, with two rtw89 driven devices in the system, channel
information may get incoherent, preventing channel use.

Signed-off-by: Ondrej Jirman <megi@xff.cz>
---
 drivers/net/wireless/realtek/rtw89/core.c | 33 +++++++++++++++++++----
 1 file changed, 28 insertions(+), 5 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtw89/core.c b/drivers/net/wireless/realtek/rtw89/core.c
index b164bc767e82..bc26790ed313 100644
--- a/drivers/net/wireless/realtek/rtw89/core.c
+++ b/drivers/net/wireless/realtek/rtw89/core.c
@@ -4400,17 +4400,40 @@ static int rtw89_init_he_eht_cap(struct rtw89_dev *rtwdev,
 	return 0;
 }
 
+static struct ieee80211_supported_band *
+rtw89_core_sband_dup(struct rtw89_dev *rtwdev,
+		     const struct ieee80211_supported_band *sband)
+{
+	struct ieee80211_supported_band *dup;
+
+	dup = devm_kmemdup(rtwdev->dev, sband, sizeof(*sband), GFP_KERNEL);
+	if (!dup)
+		return NULL;
+
+	dup->channels = devm_kmemdup(rtwdev->dev, sband->channels,
+				     sizeof(*sband->channels) * sband->n_channels,
+				     GFP_KERNEL);
+	if (!dup->channels)
+		return NULL;
+
+	dup->bitrates = devm_kmemdup(rtwdev->dev, sband->bitrates,
+				     sizeof(*sband->bitrates) * sband->n_bitrates,
+				     GFP_KERNEL);
+	if (!dup->bitrates)
+		return NULL;
+
+	return dup;
+}
+
 static int rtw89_core_set_supported_band(struct rtw89_dev *rtwdev)
 {
 	struct ieee80211_hw *hw = rtwdev->hw;
 	struct ieee80211_supported_band *sband;
-	u32 size = sizeof(struct ieee80211_supported_band);
 	u8 support_bands = rtwdev->chip->support_bands;
-	struct device *dev = rtwdev->dev;
 	int ret;
 
 	if (support_bands & BIT(NL80211_BAND_2GHZ)) {
-		sband = devm_kmemdup(dev, &rtw89_sband_2ghz, size, GFP_KERNEL);
+		sband = rtw89_core_sband_dup(rtwdev, &rtw89_sband_2ghz);
 		if (!sband)
 			return -ENOMEM;
 		rtw89_init_ht_cap(rtwdev, &sband->ht_cap);
@@ -4421,7 +4444,7 @@ static int rtw89_core_set_supported_band(struct rtw89_dev *rtwdev)
 	}
 
 	if (support_bands & BIT(NL80211_BAND_5GHZ)) {
-		sband = devm_kmemdup(dev, &rtw89_sband_5ghz, size, GFP_KERNEL);
+		sband = rtw89_core_sband_dup(rtwdev, &rtw89_sband_5ghz);
 		if (!sband)
 			return -ENOMEM;
 		rtw89_init_ht_cap(rtwdev, &sband->ht_cap);
@@ -4433,7 +4456,7 @@ static int rtw89_core_set_supported_band(struct rtw89_dev *rtwdev)
 	}
 
 	if (support_bands & BIT(NL80211_BAND_6GHZ)) {
-		sband = devm_kmemdup(dev, &rtw89_sband_6ghz, size, GFP_KERNEL);
+		sband = rtw89_core_sband_dup(rtwdev, &rtw89_sband_6ghz);
 		if (!sband)
 			return -ENOMEM;
 		ret = rtw89_init_he_eht_cap(rtwdev, NL80211_BAND_6GHZ, sband);
-- 
2.49.0

Ondřej Jirman <megi@xff.cz> wrote:
> 
> Internally wiphy writes to individual channels in this structure,
> so we must not share one static definition of channel list between
> multiple device instances, because that causes hard to debug
> breakage.
> 
> For example, with two rtw89 driven devices in the system, channel
> information may get incoherent, preventing channel use.
> 
> Signed-off-by: Ondrej Jirman <megi@xff.cz>

Acked-by: Ping-Ke Shih <pkshih@realtek.com>

Thanks for your prompt work. :-)

On Wed, Apr 30, 2025 at 12:16:47AM +0000, Ping-Ke Shih wrote:
> Ondřej Jirman <megi@xff.cz> wrote:
> > 
> > Internally wiphy writes to individual channels in this structure,
> > so we must not share one static definition of channel list between
> > multiple device instances, because that causes hard to debug
> > breakage.
> > 
> > For example, with two rtw89 driven devices in the system, channel
> > information may get incoherent, preventing channel use.
> > 
> > Signed-off-by: Ondrej Jirman <megi@xff.cz>
> 
> Acked-by: Ping-Ke Shih <pkshih@realtek.com>
> 
> Thanks for your prompt work. :-)

You're welcome. I like rtw89 supported cards very much for my home AP. I'm
glad I'll now be able to use multitudes of them in one router. :-D

Thanks for upstreaming and maintaining the Linux driver. My AP has been
working solidly for me since the driver gained AP support, which is
great, especially given how much development it's receiving.

Best regards,
	o.