txpower settings.

Acinonyx Jubatus acinonyxs
Fri Feb 11 16:38:33 PST 2005


----- Original Message ----- 
From: "Ajeet" <fromkth+hostap at fastmail.fm>
To: <hostap at shmoo.com>
Sent: Wednesday, February 09, 2005 1:52 PM
Subject: txpower settings.


> Hi,
>
> I am building a WLAN testbed(2 prism2 based APs and one prism2based STA
> ) in a small room, so need to reduce the power of APs so i can do
> handover in a small room while moving away from one AP to the other AP.
>
> I tried to used txpower option in iwconfig, but except "auto" and "off"
> other options gives following error,
>
> Error for wireless request "Set Tx Power" (8B27):
> GET failed on device wlan0 ; Operation not supoorted.
>
> So what do i need to do to reduce trasmitt power of APs.
> is it something related with ALC? there is no info about what ALC is, in
> README's or FAQ's.
>
> Thanks.
>
> -ajeet.


Hello ajeet,

you have to patch hostap to support tx power setting.
With command iwconfig wlan0 txpower 127 you have minimum tx power
With command iwconfig wlan0 txpower -128 you have maximum tx power
You may see a warning during compilation. It is OK.


The diff for 0.2.6 (don't know if it patches 0.3.x also):

diff -Naur hostap-driver-0.2.5/driver/modules/hostap.c
hostap-driver-0.2.5-patched/driver/modules/hostap.c
--- hostap-driver-0.2.5/driver/modules/hostap.c 2004-07-12
05:06:14.000000000 +0300
+++ hostap-driver-0.2.5-patched/driver/modules/hostap.c 2004-12-19
13:13:40.000000000 +0200
@@ -1155,6 +1155,36 @@
  return ret;
 }

+/* BUG FIX: Restore power setting value when lost due to F/W bug */
+
+int hostap_restore_power(struct net_device *dev)
+{
+        struct hostap_interface *iface = dev->priv;
+       local_info_t *local = iface->local;
+
+       u16 val;
+       int ret = 0;
+
+       if (local->txpower_type == PRISM2_TXPOWER_OFF) {
+                       val = 0xff; /* use all standby and sleep modes */
+                       ret = local->func->cmd(dev,
HFA384X_CMDCODE_WRITEMIF,
+                                              HFA386X_CR_A_D_TEST_MODES2,
+                                              &val, NULL);
+       }
+
+#ifdef RAW_TXPOWER_SETTING
+       if (local->txpower_type == PRISM2_TXPOWER_FIXED) {
+               val = HFA384X_TEST_CFG_BIT_ALC;
+               local->func->cmd(dev, HFA384X_CMDCODE_TEST |
+                                (HFA384X_TEST_CFG_BITS << 8), 0, &val,
NULL);
+               val = prism2_txpower_dBm_to_hfa386x(local->txpower);
+               ret = (local->func->cmd(dev, HFA384X_CMDCODE_WRITEMIF,
+                            HFA386X_CR_MANUAL_TX_POWER, &val, NULL));
+       }
+#endif /* RAW_TXPOWER_SETTING */
+       return (ret ? -EOPNOTSUPP : 0);
+}
+

 struct proc_dir_entry *hostap_proc;

@@ -1205,6 +1235,7 @@
 EXPORT_SYMBOL(hostap_set_hostapd_sta);
 EXPORT_SYMBOL(hostap_add_interface);
 EXPORT_SYMBOL(hostap_remove_interface);
+EXPORT_SYMBOL(hostap_restore_power);
 EXPORT_SYMBOL(prism2_update_comms_qual);

 module_init(hostap_init);
diff -Naur hostap-driver-0.2.5/driver/modules/hostap.h
hostap-driver-0.2.5-patched/driver/modules/hostap.h
--- hostap-driver-0.2.5/driver/modules/hostap.h 2003-11-30
04:14:26.000000000 +0200
+++ hostap-driver-0.2.5-patched/driver/modules/hostap.h 2004-12-19
13:14:28.000000000 +0200
@@ -36,6 +36,7 @@
       const char *prefix, const char *name);
 void hostap_remove_interface(struct net_device *dev, int rtnl_locked,
         int remove_from_list);
+int hostap_restore_power(struct net_device *dev);
 int prism2_update_comms_qual(struct net_device *dev);
 int prism2_sta_send_mgmt(local_info_t *local, u8 *dst, u8 stype,
     u8 *body, size_t bodylen);
diff -Naur hostap-driver-0.2.5/driver/modules/hostap_ap.c
hostap-driver-0.2.5-patched/driver/modules/hostap_ap.c
--- hostap-driver-0.2.5/driver/modules/hostap_ap.c 2004-07-18
02:34:23.000000000 +0300
+++ hostap-driver-0.2.5-patched/driver/modules/hostap_ap.c 2004-12-19
22:42:35.000000000 +0200
@@ -2346,13 +2346,13 @@
   addr[count].sa_family = ARPHRD_ETHER;
   memcpy(addr[count].sa_data, sta->addr, ETH_ALEN);
   if (sta->last_rx_silence == 0)
-   qual[count].qual = sta->last_rx_signal < 27 ?
-    0 : (sta->last_rx_signal - 27) * 92 / 127;
+                        qual[count].qual = sta->last_rx_signal < 156 ?
+                                0 : (sta->last_rx_signal - 156) * 92 / 64;
   else
-   qual[count].qual = sta->last_rx_signal -
-    sta->last_rx_silence - 35;
-  qual[count].level = HFA384X_LEVEL_TO_dBm(sta->last_rx_signal);
-  qual[count].noise = HFA384X_LEVEL_TO_dBm(sta->last_rx_silence);
+                        qual[count].qual = (sta->last_rx_signal -
+                                sta->last_rx_silence) * 92 / 64;
+                qual[count].level = sta->last_rx_signal;
+                qual[count].noise = sta->last_rx_silence;
   qual[count].updated = sta->last_rx_updated;

   sta->last_rx_updated = 0;
@@ -2413,13 +2413,13 @@
   memset(&iwe, 0, sizeof(iwe));
   iwe.cmd = IWEVQUAL;
   if (sta->last_rx_silence == 0)
-   iwe.u.qual.qual = sta->last_rx_signal < 27 ?
-    0 : (sta->last_rx_signal - 27) * 92 / 127;
+                 iwe.u.qual.qual = sta->last_rx_signal < 156 ?
+                         0 : (sta->last_rx_signal - 156) * 92 / 64;
   else
-   iwe.u.qual.qual = sta->last_rx_signal -
-    sta->last_rx_silence - 35;
-  iwe.u.qual.level = HFA384X_LEVEL_TO_dBm(sta->last_rx_signal);
-  iwe.u.qual.noise = HFA384X_LEVEL_TO_dBm(sta->last_rx_silence);
+                        iwe.u.qual.qual = (sta->last_rx_signal -
+                                sta->last_rx_silence) * 92 / 64;
+                iwe.u.qual.level = sta->last_rx_signal;
+                iwe.u.qual.noise = sta->last_rx_silence;
   iwe.u.qual.updated = sta->last_rx_updated;
   iwe.len = IW_EV_QUAL_LEN;
   current_ev = iwe_stream_add_event(current_ev, end_buf, &iwe,
diff -Naur hostap-driver-0.2.5/driver/modules/hostap_config.h
hostap-driver-0.2.5-patched/driver/modules/hostap_config.h
--- hostap-driver-0.2.5/driver/modules/hostap_config.h 2004-10-04
02:36:26.000000000 +0300
+++ hostap-driver-0.2.5-patched/driver/modules/hostap_config.h 2004-12-19
16:04:09.000000000 +0200
@@ -94,6 +94,12 @@
  */
 /* #define PRISM2_NO_STATION_MODES */

+/* Enable TX power Setting functions
+ * (min att = -128 , max att =  127)
+ */
+
+#define RAW_TXPOWER_SETTING
+
 /* Use Linux crypto API instead of own encryption implementation whenever
  * possible. */
 /* #define HOSTAP_USE_CRYPTO_API */
diff -Naur hostap-driver-0.2.5/driver/modules/hostap_hw.c
hostap-driver-0.2.5-patched/driver/modules/hostap_hw.c
--- hostap-driver-0.2.5/driver/modules/hostap_hw.c 2004-10-04
02:20:57.000000000 +0300
+++ hostap-driver-0.2.5-patched/driver/modules/hostap_hw.c 2004-12-19
21:10:23.000000000 +0200
@@ -1039,6 +1039,7 @@
          dev->name, local->fragm_threshold);
  }

+ hostap_restore_power(dev);
  return res;
 }

diff -Naur hostap-driver-0.2.5/driver/modules/hostap_info.c
hostap-driver-0.2.5-patched/driver/modules/hostap_info.c
--- hostap-driver-0.2.5/driver/modules/hostap_info.c 2004-02-29
20:05:44.000000000 +0200
+++ hostap-driver-0.2.5-patched/driver/modules/hostap_info.c 2004-12-19
22:00:46.000000000 +0200
@@ -418,6 +418,11 @@
  }

  /* Get BSSID if we have a valid AP address */
+
+ if ( val == HFA384X_LINKSTATUS_CONNECTED ||
+      val == HFA384X_LINKSTATUS_DISCONNECTED )
+   hostap_restore_power(local->dev);
+
  if (connected) {
   netif_carrier_on(local->dev);
   netif_carrier_on(local->ddev);
diff -Naur hostap-driver-0.2.5/driver/modules/hostap_ioctl.c
hostap-driver-0.2.5-patched/driver/modules/hostap_ioctl.c
--- hostap-driver-0.2.5/driver/modules/hostap_ioctl.c 2004-10-04
02:20:57.000000000 +0300
+++ hostap-driver-0.2.5-patched/driver/modules/hostap_ioctl.c 2004-12-19
16:11:42.000000000 +0200
@@ -1429,23 +1429,20 @@
   val = 255;

  tmp = val;
- tmp >>= 2;

- return -12 - tmp;
+ return tmp;
 }

 static u16 prism2_txpower_dBm_to_hfa386x(int val)
 {
  signed char tmp;

- if (val > 20)
-  return 128;
- else if (val < -43)
+ if (val > 127)
   return 127;
+ else if (val < -128)
+  return 128;

  tmp = val;
- tmp = -12 - tmp;
- tmp <<= 2;

  return (unsigned char) tmp;
 }








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