Intel 4965 HT rates

Hi,

I'm running compat-wireless-2.6.33-rc1 and iw list shows some confusing HT
capabilities:
Band 1:
HT capabilities: 0x082c
* 20 MHz operation
* SM PS disabled
* 20 MHz short GI
* max A-MSDU len 7935

but for 802.11a channels:
Band 2:
HT capabilities: 0x086e
* 20/40 MHz operation
* SM PS disabled
* 20 MHz short GI
* 40 MHz short GI
* max A-MSDU len 7935

While I can't tell when this happened, I remember older 2.6.29 releases supported HT40 for both bands.
The wireless card is an Intel 4965 on a Thinkpad T61.

Regards,
Valentin

How do you know? What makes you believe that was the case?

The ht_cap that gets parsed and sent back through nl80211 is initialized in iwl-agn on iwl-core.c on iwlcore_init_ht_hw_capab() as follows

static void iwlcore_init_ht_hw_capab(const struct iwl_priv *priv,

                              struct ieee80211_sta_ht_cap *ht_info,
                              enum ieee80211_band band)
{
        ....
        if (priv->hw_params.ht40_channel & BIT(band)) {
                ht_info->cap |= IEEE80211_HT_CAP_SUP_WIDTH_20_40;
                ht_info->cap |= IEEE80211_HT_CAP_SGI_40;
                ht_info->mcs.rx_mask[4] = 0x01;
                max_bit_rate = MAX_BIT_RATE_40_MHZ;
        }
        ....
}

And the priv->hw_params.ht40_channel gets initialized for 4965 hardware on iwl4965_hw_set_hw_params():

static int iwl4965_hw_set_hw_params(struct iwl_priv *priv)

{
        ...
        priv->hw_params.ht40_channel = BIT(IEEE80211_BAND_5GHZ);
        ....
}

iwl-5000 and iwl-6000 sets this to both bands:

int iwl5000_hw_set_hw_params(struct iwl_priv *priv)

{
        ....
        priv->hw_params.ht40_channel =  BIT(IEEE80211_BAND_2GHZ) |
                                        BIT(IEEE80211_BAND_5GHZ);
        ....
}

static int iwl6000_hw_set_hw_params(struct iwl_priv *priv)

{
        ....
        priv->hw_params.ht40_channel =  BIT(IEEE80211_BAND_2GHZ) |
                                        BIT(IEEE80211_BAND_5GHZ);
        ....
}

So it appears to be done explicitly in software, not sure if hardware does support HT40 on 2.4 GHz band on the 4965, Intel folks would though.

Luis

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Except its called priv->hw_params.fat_channel there.

Luis

AFAIK the Windows driver supports 2GHz HT40 for all cards, but disables it by default, even for IWL5/6xxx.

Vista: [V]iruses, [I]ntruders, [S]pyware, [T]rojans and [A]dware. :-)

Hmmm,

Sorry, you are right, Intel describes this as a feature for the 4965. I was
probably running a very old driver(it was before they added support for the 5000 series), because I remember specifically the router reporting a 117Mbs bitrate.
I'm still trying to track down that driver as it seems quite silly to have this artificial limitation.

Thanks,
Valentin