| Message ID | CAN8YU5Mxxqs1H4caXQ_tS0Sq5YKwk9NatgSqWferCqBu_+jnyQ@mail.gmail.com (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
Hi Andrea, On Sat, 2014-05-31 at 20:54 +0200, Andrea Merello wrote: > Hello, > I found some useful helper function in mac80211, and I used some of > them, but unfortunately I finally parsed information element in > beacon/probe-response by myself: > I found the utility ieee802_11_parse_elems(), but it seems that it > relies on structures that are declared in some .h file located locally > to mac80211.. So I suppose it is not intended for use outside > mac80211, is it? Yeah, and it would do much more than what you want. You could use cfg80211_find_ie() though to simplify the code. > +/* This is a workaround to make scan working: > + * currently mac80211 does not process frames with no frequency > + * information. > + * However during scan the HW performs a sweep by itself, and we > + * are unable to know where the radio is actually tuned. > + * This function tries to do its best to guess this information.. > + * If the current frame is a beacon or a probe response, the channel > + * information is extracted from it. > + * For other frames, or if it happen that for whatever reason we fail > + * to parse beacons and probe responses, this function returns > + * the priv->channel information, that should be valid at least > + * when we are NOT scanning. > + */ > +static int at76_parse_freq(struct at76_priv *priv) > +{ > + size_t el_off; > + u8 id; > + u8 *el; > + int el_len; > + int channel = priv->channel; > + int len = priv->rx_skb->len; > + struct ieee80211_hdr *hdr = (void *)priv->rx_skb->data; > + > + if (len < 24) > + goto exit; > + > + if (ieee80211_is_probe_resp(hdr->frame_control)) { > + el_off = offsetof(struct ieee80211_mgmt, u.probe_resp.variable); > + el = ((struct ieee80211_mgmt *)hdr)->u.probe_resp.variable; > + } else if (ieee80211_is_beacon(hdr->frame_control)) { > + el_off = offsetof(struct ieee80211_mgmt, u.beacon.variable); > + el = ((struct ieee80211_mgmt *)hdr)->u.beacon.variable; > + } else > + goto exit; > + > + len -= el_off; > + > + while (len >= 2) { > + id = *el++; > + el_len = *el++; > + len -= 2; > + > + if (id == WLAN_EID_DS_PARAMS) { > + if ((el_len > 0) && (len >= el_len)) > + channel = *el; > + break; > + } > + len -= el_len; > + el += el_len; > + } So the loop can be simplified to el = cfg80211_find_ie(WLAN_EID_DS_PARAMS, el, el_len); if (el && el[1] > 0) channel = el[2]; > @@ -1542,6 +1597,8 @@ static void at76_rx_tasklet(unsigned long param) > rx_status.signal = buf->rssi; > rx_status.flag |= RX_FLAG_DECRYPTED; > rx_status.flag |= RX_FLAG_IV_STRIPPED; > + rx_status.band = IEEE80211_BAND_2GHZ; > + rx_status.freq = at76_parse_freq(priv); You might also invoke this only when you know you're scanning, to avoid the overhead otherwise, but with this driver it probably doesn't matter much. johannes -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/net/wireless/at76c50x-usb.c b/drivers/net/wireless/at76c50x-usb.c index 10fd12e..06a64f4 100644 --- a/drivers/net/wireless/at76c50x-usb.c +++ b/drivers/net/wireless/at76c50x-usb.c @@ -1502,6 +1502,61 @@ static void at76_work_submit_rx(struct work_struct *work) mutex_unlock(&priv->mtx); } +/* This is a workaround to make scan working: + * currently mac80211 does not process frames with no frequency + * information. + * However during scan the HW performs a sweep by itself, and we + * are unable to know where the radio is actually tuned. + * This function tries to do its best to guess this information.. + * If the current frame is a beacon or a probe response, the channel + * information is extracted from it. + * For other frames, or if it happen that for whatever reason we fail + * to parse beacons and probe responses, this function returns + * the priv->channel information, that should be valid at least + * when we are NOT scanning. + */ +static int at76_parse_freq(struct at76_priv *priv) +{ + size_t el_off; + u8 id; + u8 *el; + int el_len; + int channel = priv->channel; + int len = priv->rx_skb->len; + struct ieee80211_hdr *hdr = (void *)priv->rx_skb->data; + + if (len < 24) + goto exit; + + if (ieee80211_is_probe_resp(hdr->frame_control)) { + el_off = offsetof(struct ieee80211_mgmt, u.probe_resp.variable); + el = ((struct ieee80211_mgmt *)hdr)->u.probe_resp.variable; + } else if (ieee80211_is_beacon(hdr->frame_control)) { + el_off = offsetof(struct ieee80211_mgmt, u.beacon.variable); + el = ((struct ieee80211_mgmt *)hdr)->u.beacon.variable; + } else + goto exit; + + len -= el_off; + + while (len >= 2) { + id = *el++; + el_len = *el++; + len -= 2; + + if (id == WLAN_EID_DS_PARAMS) { + if ((el_len > 0) && (len >= el_len)) + channel = *el; + break; + } + len -= el_len; + el += el_len; + } + +exit: + return ieee80211_channel_to_frequency(channel, IEEE80211_BAND_2GHZ); +} + static void at76_rx_tasklet(unsigned long param) { struct urb *urb = (struct urb *)param; @@ -1542,6 +1597,8 @@ static void at76_rx_tasklet(unsigned long param) rx_status.signal = buf->rssi; rx_status.flag |= RX_FLAG_DECRYPTED; rx_status.flag |= RX_FLAG_IV_STRIPPED; + rx_status.band = IEEE80211_BAND_2GHZ; + rx_status.freq = at76_parse_freq(priv); at76_dbg(DBG_MAC80211, "calling ieee80211_rx_irqsafe(): %d/%d", priv->rx_skb->len, priv->rx_skb->data_len);