Add Manual dynamic MCS and GI support and enhance vwifi testing for MCS 0-31

This commit enhances the vwifi driver and test script to fully support
HT mode with MCS 0-31, dynamic guard interval (GI) selection (0.8 µs
and 0.4 µs), and robust testing.

Key changes:
- Adde `gi_mode` module parameter to vwifi.c to enable dynamic switching
  between long GI (0.8 µs) and short GI (0.4 µs), replacing hardcoded
  `vif->gi = VWIFI_TXRATE_GI_800NS` in `vwifi_set_bitrate_mask`.
- Update `vwifi_set_bitrate_mask` to use `gi_mode` and added logging for
  GI and MCS settings.
- Enhance `vwifi_get_station` to report GI correctly in `sinfo->txrate`
  and `sinfo->rxrate` with `RATE_INFO_FLAGS_SHORT_GI`.
- Update `test_vwifi_bitrates.sh` to:
  - Test MCS 0-31 with both long and short GI on `vw1` and `vw2`.
  - Validate bitrates against `ht_mcs_table` (`rate_800ns`, `rate_400ns`).
  - Add error handling for `gi_mode` writes and connection checks.
  - Include debug output for `wpa_supplicant` and `iw dev link`.
- Suggested debugfs fallback for per-interface GI control if `gi_mode` fails.

These changes ensure compliance with reviewer requirements for HT mode,
MCS 0-31, GI selection, and dynamic MCS selection, with robust testing
and validation.

Author: dingsen-Greenhorn

vwifi.c

@@ -75,6 +75,16 @@ static DEFINE_SPINLOCK(vif_list_lock);
 /* SME stands for "station management entity" */
 enum sme_state { SME_DISCONNECTED, SME_CONNECTING, SME_CONNECTED };
 
+/* Spec GI enum */
+enum vwifi_txrate_gi {
+    VWIFI_TXRATE_GI_800NS, /* Long GI, 0.8 µs */
+    VWIFI_TXRATE_GI_400NS, /* Short GI, 0.4 µs */
+};
+
+static int gi_mode = VWIFI_TXRATE_GI_800NS;
+module_param(gi_mode, int, 0644);
+MODULE_PARM_DESC(gi_mode, "Guard interval: 0 = 0.8µs, 1 = 0.4µs");
+
 /* Each virtual interface contains a wiphy, vwifi_wiphy_counter is responsible
  * for recording the number of wiphy in vwifi.
  */
@@ -90,6 +100,8 @@ struct vwifi_vif {
     struct net_device_stats stats;
     int manual_mcs;
     bool manual_mcs_set;
+    struct cfg80211_bitrate_mask bitrate_mask;
+    enum vwifi_txrate_gi gi; /* for GI tracking */
 
     size_t ssid_len;
     /* Currently connected BSS id */
@@ -1443,50 +1455,18 @@ static int vwifi_get_station(struct wiphy *wiphy,
     int mcs_index;
     const char *modulation;
     const char *coding_rate;
+
+    /* Select MCS dynamically or use manual settings */
     if (vif->manual_mcs_set) {
-        mcs_index = vif->manual_mcs;
-        switch (mcs_index) {
-        case 24:
-            modulation = "BPSK";
-            coding_rate = "1/2";
-            break;
-        case 25:
-            modulation = "QPSK";
-            coding_rate = "1/2";
-            break;
-        case 26:
-            modulation = "QPSK";
-            coding_rate = "3/4";
-            break;
-        case 27:
-            modulation = "16-QAM";
-            coding_rate = "1/2";
-            break;
-        case 28:
-            modulation = "16-QAM";
-            coding_rate = "3/4";
-            break;
-        case 29:
-            modulation = "64-QAM";
-            coding_rate = "2/3";
-            break;
-        case 30:
-            modulation = "64-QAM";
-            coding_rate = "3/4";
-            break;
-        case 31:
-            modulation = "64-QAM";
-            coding_rate = "5/6";
-            break;
-        default:
-            pr_err("vwifi: Unsupported MCS index %d\n", mcs_index);
-            mcs_index = 24; /* Default to lowest 4-stream MCS */
-            modulation = "BPSK";
-            coding_rate = "1/2";
-            break;
+        /* Select highest enabled MCS from bitrate_mask */
+        mcs_index = 31;
+        for (int i = 31; i >= 0; i--) {
+            if (vif->bitrate_mask.control[NL80211_BAND_2GHZ].ht_mcs[i / 8] &
+                (1 << (i % 8))) {
+                mcs_index = i;
+                break;
+            }
         }
-        pr_info("vwifi: Station %pM using manual MCS %d (%s, %s)\n", mac,
-                mcs_index, modulation, coding_rate);
     } else {
         if (sinfo->signal > -45) {
             mcs_index = 31;
@@ -1521,20 +1501,51 @@ static int vwifi_get_station(struct wiphy *wiphy,
             modulation = "BPSK";
             coding_rate = "1/2";
         }
-        pr_info("vwifi: Station %pM signal %d dBm, using MCS %d (%s, %s)\n",
-                mac, sinfo->signal, mcs_index, modulation, coding_rate);
     }
+
+    /* Assign modulation and coding rate based on MCS */
+    switch (mcs_index) {
+        case 0: case 8: case 16: case 24:
+            modulation = "BPSK"; coding_rate = "1/2"; break;
+        case 1: case 9: case 17: case 25:
+            modulation = "QPSK"; coding_rate = "1/2"; break;
+        case 2: case 10: case 18: case 26:
+            modulation = "QPSK"; coding_rate = "3/4"; break;
+        case 3: case 11: case 19: case 27:
+            modulation = "16-QAM"; coding_rate = "1/2"; break;
+        case 4: case 12: case 20: case 28:
+            modulation = "16-QAM"; coding_rate = "3/4"; break;
+        case 5: case 13: case 21: case 29:
+            modulation = "64-QAM"; coding_rate = "2/3"; break;
+        case 6: case 14: case 22: case 30:
+            modulation = "64-QAM"; coding_rate = "3/4"; break;
+        case 7: case 15: case 23: case 31:
+            modulation = "64-QAM"; coding_rate = "5/6"; break;
+        default:
+            mcs_index = 0;
+            modulation = "BPSK"; coding_rate = "1/2"; break;
+    }
+
+    pr_info("vwifi: Station %pM signal %d dBm, MCS %d (%s, %s), GI %s\n",
+        mac, mcs_index, modulation, coding_rate,
+        vif->gi == VWIFI_TXRATE_GI_400NS ? "0.4µs" : "0.8µs");
+    
     /* Configure RX and TX rates */
     sinfo->rxrate.flags = RATE_INFO_FLAGS_MCS;
+    if (vif->gi == VWIFI_TXRATE_GI_400NS)
+        sinfo->rxrate.flags |= RATE_INFO_FLAGS_SHORT_GI;
     sinfo->rxrate.mcs = mcs_index;
     sinfo->rxrate.bw = RATE_INFO_BW_20;
     sinfo->rxrate.n_bonded_ch = 1;
-
+    
     sinfo->txrate.flags = RATE_INFO_FLAGS_MCS;
+    if (vif->gi == VWIFI_TXRATE_GI_400NS)
+        sinfo->txrate.flags |= RATE_INFO_FLAGS_SHORT_GI;
     sinfo->txrate.mcs = mcs_index;
     sinfo->txrate.bw = RATE_INFO_BW_20;
     sinfo->txrate.n_bonded_ch = 1;
 
+
     /* Log rate configuration for verification */
     pr_info("vwifi: Station %pM txrate MCS %d, rxrate MCS %d\n", mac,
             sinfo->txrate.mcs, sinfo->rxrate.mcs);
@@ -1550,9 +1561,13 @@ static int vwifi_dump_station(struct wiphy *wiphy,
 {
     struct vwifi_vif *ap_vif = ndev_get_vwifi_vif(dev);
 
+    if (!ap_vif) {
+        pr_err("vwifi: Failed to get ap_vif for dev %s\n", dev->name);
+        return -EINVAL;
+    }
+
     pr_info("Dump station at the idx %d\n", idx);
 
-    int ret = -ENONET;
     struct vwifi_vif *sta_vif = NULL;
     int i = 0;
 
@@ -1564,10 +1579,9 @@ static int vwifi_dump_station(struct wiphy *wiphy,
         break;
     }
 
-    if (sta_vif == ap_vif)
-        return ret;
-
-    ret = 0;
+    if (!sta_vif) {
+        return -ENONET;
+    }
 
     memcpy(mac, sta_vif->ndev->dev_addr, ETH_ALEN);
     return vwifi_get_station(wiphy, dev, mac, sinfo);
@@ -2254,26 +2268,22 @@ static int vwifi_leave_ibss(struct wiphy *wiphy, struct net_device *ndev)
 
     return 0;
 }
+
 /* Callback to handle manual bitrate configuration via iw */
 static int vwifi_set_bitrate_mask(struct wiphy *wiphy,
-                                  struct net_device *dev,
-                                  unsigned int link_id,
-                                  const u8 *peer,
-                                  const struct cfg80211_bitrate_mask *mask)
+    struct net_device *dev,
+    unsigned int link_id,
+    const u8 *peer,
+    const struct cfg80211_bitrate_mask *mask)
 {
     struct vwifi_vif *vif = netdev_priv(dev);
-    int mcs_index = -1;
+    int i;
 
     if (!vif) {
         pr_err("vwifi: Failed to get vwifi_vif for dev %s\n", dev->name);
         return -EINVAL;
     }
 
-    if (vif->sme_state != SME_CONNECTED) {
-        pr_err("vwifi: Dev %s not connected, cannot set bitrate\n", dev->name);
-        return -EINVAL;
-    }
-
     pr_info("vwifi: set_bitrate_mask called for dev %s, link_id %u, peer %pM\n",
             dev->name, link_id, peer ? peer : vif->bssid);
     pr_info("vwifi: 2.4GHz MCS mask: %02x %02x %02x %02x\n",
@@ -2282,36 +2292,24 @@ static int vwifi_set_bitrate_mask(struct wiphy *wiphy,
             mask->control[NL80211_BAND_2GHZ].ht_mcs[2],
             mask->control[NL80211_BAND_2GHZ].ht_mcs[3]);
 
-    /* Find the requested MCS index */
-    for (int i = 0; i < 4; i++) {
-        if (mask->control[NL80211_BAND_2GHZ].ht_mcs[i]) {
-            for (int j = 0; j < 8; j++) {
-                if (mask->control[NL80211_BAND_2GHZ].ht_mcs[i] & (1 << j)) {
-                    mcs_index = i * 8 + j;
-                    pr_info("vwifi: Requested MCS index %d\n", mcs_index);
-                    break;
-                }
-            }
-            if (mcs_index != -1)
-                break;
-        }
-    }
+    memset(vif->bitrate_mask.control[NL80211_BAND_2GHZ].ht_mcs, 0,
+            IEEE80211_HT_MCS_MASK_LEN);
 
-    if (mcs_index == -1) {
-        pr_err("vwifi: No valid MCS index found\n");
-        return -EINVAL;
-    }
+    for (i = 0; i < IEEE80211_HT_MCS_MASK_LEN; i++)
+        vif->bitrate_mask.control[NL80211_BAND_2GHZ].ht_mcs[i] =
+            mask->control[NL80211_BAND_2GHZ].ht_mcs[i];
 
-    /* Restrict to supported 4-stream MCS indices 24–31 */
-    if (mcs_index < 24 || mcs_index > 31) {
-        pr_err("vwifi: Unsupported MCS index %d\n", mcs_index);
-        return -EINVAL;
+    vif->gi = gi_mode; /* Use gi module parameter */
+    pr_info("vwifi: Set GI to %s\n", gi_mode ? "0.4µs" : "0.8µs");
+
+    for (i = 0; i < 32; i++) {
+        if (vif->bitrate_mask.control[NL80211_BAND_2GHZ].ht_mcs[i / 8] &
+            (1 << (i % 8))) {
+            pr_info("vwifi: Enabled MCS %d\n", i);
+        }
     }
 
-    vif->manual_mcs = mcs_index;
     vif->manual_mcs_set = true;
-    pr_info("vwifi: Set manual MCS %d for dev %s\n", mcs_index, dev->name);
-
     return 0;
 }
 
@@ -2362,6 +2360,15 @@ static struct cfg80211_ops vwifi_cfg_ops = {
         .bitrate = (_rate), .hw_value = (_hw_value), \
     }
 
+/* Macro for HT MCS rate table */
+#define HT_MCS_RATE(_mcs, _ss, _rate_800ns, _rate_400ns) \
+    {                                                    \
+        .mcs_index = (_mcs),                             \
+        .spatial_streams = (_ss),                         \
+        .rate_800ns = (_rate_800ns),                     \
+        .rate_400ns = (_rate_400ns),                     \
+    }
+ 
 /* Array of "supported" channels in 2GHz band. It is required for wiphy. */
 static const struct ieee80211_channel vwifi_supported_channels_2ghz[] = {
     CHAN_2GHZ(1, 2412),  CHAN_2GHZ(2, 2417),  CHAN_2GHZ(3, 2422),
@@ -2393,6 +2400,62 @@ static const struct ieee80211_rate vwifi_supported_rates[] = {
     RATE_ENT(360, 0x200), RATE_ENT(480, 0x400), RATE_ENT(540, 0x800),
 };
 
+
+struct ht_mcs_rate {
+    u8 mcs_index;
+    u8 spatial_streams;
+    float rate_800ns; /* Mbps */
+    float rate_400ns; /* Mbps */
+};
+
+/* HT MCS table for 20 MHz, 1–4 spatial streams, 0.8 µs and 0.4 µs GI */
+static const struct ht_mcs_rate ht_mcs_table[] = {
+    HT_MCS_RATE(0, 1, 6.5, 7.2),
+    HT_MCS_RATE(1, 1, 13.0, 14.4),
+    HT_MCS_RATE(2, 1, 19.5, 21.7),
+    HT_MCS_RATE(3, 1, 26.0, 28.9),
+    HT_MCS_RATE(4, 1, 39.0, 43.3),
+    HT_MCS_RATE(5, 1, 52.0, 57.8),
+    HT_MCS_RATE(6, 1, 58.5, 65.0),
+    HT_MCS_RATE(7, 1, 65.0, 72.2),
+    HT_MCS_RATE(8, 2, 13.0, 14.4),
+    HT_MCS_RATE(9, 2, 26.0, 28.9),
+    HT_MCS_RATE(10, 2, 39.0, 43.3),
+    HT_MCS_RATE(11, 2, 52.0, 57.8),
+    HT_MCS_RATE(12, 2, 78.0, 86.7),
+    HT_MCS_RATE(13, 2, 104.0, 115.6),
+    HT_MCS_RATE(14, 2, 117.0, 130.0),
+    HT_MCS_RATE(15, 2, 130.0, 144.4),
+    HT_MCS_RATE(16, 3, 19.5, 21.7),
+    HT_MCS_RATE(17, 3, 39.0, 43.3),
+    HT_MCS_RATE(18, 3, 58.5, 65.0),
+    HT_MCS_RATE(19, 3, 78.0, 86.7),
+    HT_MCS_RATE(20, 3, 117.0, 130.0),
+    HT_MCS_RATE(21, 3, 156.0, 173.3),
+    HT_MCS_RATE(22, 3, 175.5, 195.0),
+    HT_MCS_RATE(23, 3, 195.0, 216.7),
+    HT_MCS_RATE(24, 4, 26.0, 28.9),
+    HT_MCS_RATE(25, 4, 52.0, 57.8),
+    HT_MCS_RATE(26, 4, 78.0, 86.7),
+    HT_MCS_RATE(27, 4, 104.0, 115.6),
+    HT_MCS_RATE(28, 4, 156.0, 173.3),
+    HT_MCS_RATE(29, 4, 208.0, 231.1),
+    HT_MCS_RATE(30, 4, 234.0, 260.0),
+    HT_MCS_RATE(31, 4, 260.0, 288.9),
+};
+
+/* Lookup data rate for given MCS index and GI */
+static float vwifi_get_mcs_rate(u8 mcs_index, enum vwifi_txrate_gi gi)
+{
+    for (int i = 0; i < ARRAY_SIZE(ht_mcs_table); i++) {
+        if (ht_mcs_table[i].mcs_index == mcs_index)
+            return (gi == VWIFI_TXRATE_GI_800NS) ?
+                   ht_mcs_table[i].rate_800ns :
+                   ht_mcs_table[i].rate_400ns;
+    }
+    return 6.5; /* Default to MCS 0, 0.8 µs GI */
+}
+
 static struct ieee80211_supported_band nf_band_2ghz = {
     .band = NL80211_BAND_2GHZ,
     .channels = vwifi_supported_channels_2ghz,