[Madwifi-devel] Help with 5 and 10 MHz channels in 11g band

[Aditya B. <ay...@an...>]

Hi,

In my project, I have to work with 5/10 MHz channels in the 11g band. So 
I changed DEF_REGDMN to FCC5_FCCB in ah_regdomain.c in the SVN branch of 
MadWifi

By printing out the output of ath_hal_init_channels() inside 
ath_getchannels() in if_ath.c, I found that several channels were given 
the same channel number. For example see channel 1 in the below output

Jun 24 16:55:00 AdLenovoLinux kernel: [25818.825068] MadWifi: 
ath_getchannels: Channel   1 (2412 MHz) Max Tx Power 20 dBm (hw limited) 
[20 hw 27 reg] Flags CF_INDOOR CF_OUTDOOR CF_CCK CF_2GHZ
Jun 24 16:55:00 AdLenovoLinux kernel: [25818.825073] MadWifi: 
ath_getchannels: Channel   1 (2412 MHz) Max Tx Power 20 dBm (hw limited) 
[20 hw 27 reg] Flags CF_INDOOR CF_OUTDOOR CF_OFDM CF_2GHZ
Jun 24 16:55:00 AdLenovoLinux kernel: [25818.825077] MadWifi: 
ath_getchannels: Channel   1 (2412 MHz) Max Tx Power 20 dBm (hw limited) 
[20 hw 27 reg] Flags CF_INDOOR CF_OUTDOOR CF_OFDM CF_2GHZ CF_HALF_RATE
Jun 24 16:55:00 AdLenovoLinux kernel: [25818.825082] MadWifi: 
ath_getchannels: Channel   1 (2412 MHz) Max Tx Power 20 dBm (hw limited) 
[20 hw 27 reg] Flags CF_INDOOR CF_OUTDOOR CF_OFDM CF_2GHZ CF_QUARTER_RATE

Since I want to use 5/10 MHz channels, I wrote a function 
calcChannelNumber() that is used by ath_hal_mhz2ieee to calculate 
channel numbers in the 11g band that replaces the following line

return ((int)freq - 2407) / 5;

This function is coded as below
int calcChannelNumber(u_int freq, u_int flags)
{
     static int adder = 0;
     static u_int lastFreq = 0;
     int channelNumber;

     if(lastFreq == 0)    // first time this function is called
         lastFreq = freq;
     else if(lastFreq != freq)    // frequency has changed
          {
             lastFreq = freq;    // change the frequency
             adder += 2;
          }

     channelNumber = ((int)freq - 2407) / 5;
     channelNumber += adder;

     if(flags & CHANNEL_HALF)
         channelNumber++;
     else if(flags & CHANNEL_QUARTER)
         channelNumber += 2;

     return channelNumber;

}

Essentially, this function gives two 20 MHz channels (one with CCK and 
one with OFDM) the same number and the HALF and QUARTER rate channels 
consecutive higher numbers. Now the output from the kernel logs looks 
like this

Jun 24 17:00:51 AdLenovoLinux kernel: [26170.690224] MadWifi: 
ath_getchannels: Channel   1 (2412 MHz) Max Tx Power 20 dBm (hw limited) 
[20 hw 27 reg] Flags CF_INDOOR CF_OUTDOOR CF_CCK CF_2GHZ
Jun 24 17:00:51 AdLenovoLinux kernel: [26170.690228] MadWifi: 
ath_getchannels: Channel   1 (2412 MHz) Max Tx Power 20 dBm (hw limited) 
[20 hw 27 reg] Flags CF_INDOOR CF_OUTDOOR CF_OFDM CF_2GHZ
Jun 24 17:00:51 AdLenovoLinux kernel: [26170.690232] MadWifi: 
ath_getchannels: Channel   2 (2412 MHz) Max Tx Power 20 dBm (hw limited) 
[20 hw 27 reg] Flags CF_INDOOR CF_OUTDOOR CF_OFDM CF_2GHZ CF_HALF_RATE
Jun 24 17:00:51 AdLenovoLinux kernel: [26170.690237] MadWifi: 
ath_getchannels: Channel   3 (2412 MHz) Max Tx Power 20 dBm (hw limited) 
[20 hw 27 reg] Flags CF_INDOOR CF_OUTDOOR CF_OFDM CF_2GHZ CF_QUARTER_RATE

This can also be verified from the output below

ayb@AdLenovoLinux:~/scripts$ sudo wlanconfig ath0 list chans
Channel   1 : 2412   Mhz 11g
Channel   2 : 2412   Mhz 11g Half
Channel   3 : 2412   Mhz 11g Quarter
Channel   4 : 2417   Mhz 11g
Channel   5 : 2417   Mhz 11g Half
Channel   6 : 2417   Mhz 11g Quarter
Channel   7 : 2422   Mhz 11g
Channel   8 : 2422   Mhz 11g Half
Channel   9 : 2422   Mhz 11g Quarter
Channel  10 : 2427   Mhz 11g
Channel  11 : 2427   Mhz 11g Half
Channel  12 : 2427   Mhz 11g Quarter
Channel  13 : 2432   Mhz 11g
.................
Channel  33 : 2462   Mhz 11g Quarter

However when I try to configure the AP and STA on any HALF or QUARTER 
rate 11g channel, the STA cannot associate with the AP and keeps on 
scanning. In the kernel logs, by adding a few printk's, I found that the 
ath_hal_reset() function keeps getting called.

Can someone help me with this? Am I doing anything wrong or is there a 
better way to get access to these HALF/QUARTER rate channels?

Thanks
regards,
Aditya Bhave