On Sun, Dec 20, 2009 at 5:10 AM, Valentin Manea <linux-wireless@xxxxxx> wrote:
> 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.
How do you know? What makes you believe that was the case?
> The wireless card is an Intel 4965 on a Thinkpad T61.
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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