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Re: [RFC][PATCH] mac80211: fix VHT 160Mhz bandwidth when using extended NSS on PHY with NSS ratio

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On 5/16/2022 1:39 AM, Maxime Bizon wrote:

A PHY supporting 160Mhz with a reduced number of NSS may not have any

note correct abbreviation is: MHz
and it is suggested to use a space to separate the value from the units

of the IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_MASK bits set.

For exemple, the QCA9984 is 4x4, but can only do 2x2 VHT160 or

s/exemple/example/

80+80. The corresponding VHT capabilities should be:
  - IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_MASK == 0
  - Extended NSS BW == 2

If we use that hardware in AP mode, and a 160Mhz 2x2 STA without NSS
restriction connects to it, then that STA will set
IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_MASK to 1.

The usual logic of using bitwise-and with our own capabilities does
not work here, the current code clears the SUPP_CHAN_WIDTH bits and
resolve STA bandwidth to 80Mhz instead of 160Mhz, fix this.

Signed-off-by: Maxime Bizon <mbizon@xxxxxxxxxx>
---
  net/mac80211/vht.c | 6 ++++--
  1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/mac80211/vht.c b/net/mac80211/vht.c
index e856f9092137..7ef93adc4f24 100644
--- a/net/mac80211/vht.c
+++ b/net/mac80211/vht.c
@@ -230,9 +230,11 @@ ieee80211_vht_cap_ie_to_sta_vht_cap(struct ieee80211_sub_if_data *sdata,
  	       sizeof(struct ieee80211_vht_mcs_info));
/* copy EXT_NSS_BW Support value or remove the capability */
-	if (ieee80211_hw_check(&sdata->local->hw, SUPPORTS_VHT_EXT_NSS_BW))
+	if (ieee80211_hw_check(&sdata->local->hw, SUPPORTS_VHT_EXT_NSS_BW)) {
+		vht_cap->cap |= cap_info &
+			IEEE80211_VHT_CAP_SUPP_CHAN_WIDTH_MASK;
  		vht_cap->cap |= (cap_info & IEEE80211_VHT_CAP_EXT_NSS_BW_MASK);
-	else
+	} else

per the coding style when you use braces on any leg of if/else, use them on all legs

  		vht_cap->vht_mcs.tx_highest &=
  			~cpu_to_le16(IEEE80211_VHT_EXT_NSS_BW_CAPABLE);




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