Jiri Benc wrote:
> On Wed, 20 Jun 2007 10:10:25 +0800, Hong Liu wrote:
>> What is the meaning of IEEE80211_CHAN_W_SCAN flag? I can't find any
>> description of this flag.
>
> It means we can tune to that channel. That way you can have all
> channels the hardware support in the channel list in ieee80211_hw_mode
> struct and mask out channels disallowed by the regulations.
The following isn't in patch form; thought I'd write it up for some
discussion purposes....
SCAN renamed TUNE, and a couple adds:
/**
* enum ieee80211_channel_flags - Channel flag bit values
* @IEEE80211_CHAN_W_TUNE: Hardware can tune to this channel
* @IEEE80211_CHAN_W_ACTIVE: Channel can be used for active scanning
* @IEEE80211_CHAN_W_IBSS: Hardware can act as IBSS Master
* @IEEE80211_CHAN_W_RADAR: Radar spectrum enforcement applies
* @IEEE80211_CHAN_W_TX_ALLOWED: Tx is allowed
*
* Any channel can be added to ieee80211_hw_mode. If the TUNE flag
* is not set, however, the channel will never be used.
*
* When the ACTIVE bit is set, probe requests can be sent
* during scans. If the ACTIVE bit is not set, a probe request
* can only be sent if other 802.11 traffic is detected.
*
* In order to support IBSS mode, a channel must have both the
* ACTIVE and IBSS bits set.
*
* On channels where RADAR is set, certain restrictions apply
* regarding when a channel can be used. If the client hardware
* can detect and enforce RF silence upon radar detection, then
* the client can transmit on RADAR channels regardless of if
* other 802.11 RF activity exists on the channel. If, however
* the client hardware can not detect and enforce RF silence
* on a radar channel, the client must "follow" another source
* of 802.11 traffic. This means no transmission is allowed
* on a RADAR channel *until* traffic from a 802.11 access point
* has been detected. And then traffic can only be allowed so
* long as that AP exists and is within range (so that 802.11h
* CSA frames can be received).
*
* A channel without the TX_ALLOWED bit set *can not* be used
* for any type of transmission and can only be used for passive
* listening. This is useful for performing network audits.
*
* When using the legacy wireless extension SIOGIWRANGE, only
* channels with the TUNE and TX_ALLOWED bits will be
* returned. Most users of SIOGIWRANGE expect to be able to
* use the returned results for a network association -- the
* lack of being able to tune or transmit make a channel
* unusable in that situation.
*/
enum ieee80211_channel_flags {
IEEE80211_CHAN_W_TUNE = (1 << 0),
IEEE80211_CHAN_W_ACTIVE_SCAN = (1 << 1),
IEEE80211_CHAN_W_IBSS = (1 << 2),
IEEE80211_CHAN_W_RADAR = (1 << 3),
IEEE80211_CHAN_W_TX_ALLOWED = (1 << 4),
};
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