[PATCH 6.18.y] wifi: mt76: mt792x: fix negative errno truncation in offload capability

[Yi Cong <cong.yi@linux.dev>]

From: Yi Cong <yicong@kylinos.cn>

Returning a negative errno as u8 turned -ENOENT into 0xfe, wrongly
enabling CNM and NAN caps. Return int and default to no caps on error.

Fixes: e8a264ccd2de ("wifi: mt76: mt7921: move init shared code in mt792x-lib module")
Cc: stable@vger.kernel.org
Signed-off-by: Yi Cong <yicong@kylinos.cn>
Link: https://patch.msgid.link/20260824021429.43761-1-cong.yi@linux.dev
Signed-off-by: Felix Fietkau <nbd@nbd.name>
(cherry picked from commit d0115096429ca090a592770c7645f9553a839954)
---
 drivers/net/wireless/mediatek/mt76/mt792x_core.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt792x_core.c b/drivers/net/wireless/mediatek/mt76/mt792x_core.c
index 96c50a501c1a..d00807075c71 100644
--- a/drivers/net/wireless/mediatek/mt76/mt792x_core.c
+++ b/drivers/net/wireless/mediatek/mt76/mt792x_core.c
@@ -704,7 +704,7 @@ int mt792x_init_wiphy(struct ieee80211_hw *hw)
 }
 EXPORT_SYMBOL_GPL(mt792x_init_wiphy);
 
-static u8
+static int
 mt792x_get_offload_capability(struct device *dev, const char *fw_wm)
 {
 	const struct mt76_connac2_fw_trailer *hdr;
@@ -766,13 +766,20 @@ mt792x_get_mac80211_ops(struct device *dev,
 			void *drv_data, u8 *fw_features)
 {
 	struct ieee80211_ops *ops;
+	int ret;
 
 	ops = devm_kmemdup(dev, mac80211_ops, sizeof(struct ieee80211_ops),
 			   GFP_KERNEL);
 	if (!ops)
 		return NULL;
 
-	*fw_features = mt792x_get_offload_capability(dev, drv_data);
+	ret = mt792x_get_offload_capability(dev, drv_data);
+	if (ret < 0) {
+		dev_warn(dev, "failed to read firmware offload caps: %d\n", ret);
+		*fw_features = 0;
+	} else {
+		*fw_features = ret;
+	}
 	if (!(*fw_features & MT792x_FW_CAP_CNM)) {
 		ops->remain_on_channel = NULL;
 		ops->cancel_remain_on_channel = NULL;
-- 
2.25.1