[MAC80211]: improved short preamble handling

Similarly to CTS protection, whether short preambles are used for 802.11b
transmissions should be a per-subif setting, not device global.

For STAs, this patch makes short preamble handling automatic based on the ERP
IE. For APs, hostapd still uses the prism ioctls, but the write ioctl has been
restricted to AP-only subifs.

ieee80211_txrx_data.short_preamble (an unused field) was removed.

Unfortunately, some API changes were required for the following functions:
 - ieee80211_generic_frame_duration
 - ieee80211_rts_duration
 - ieee80211_ctstoself_duration
 - ieee80211_rts_get
 - ieee80211_ctstoself_get
Affected drivers were updated accordingly.

Signed-off-by: Daniel Drake <dsd@gentoo.org>
Signed-off-by: Jiri Benc <jbenc@suse.cz>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index e76a58678959..b0af6e9f5319 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -127,7 +127,6 @@ struct ieee80211_txrx_data {
                         struct ieee80211_tx_control *control;
                         unsigned int unicast:1;
                         unsigned int ps_buffered:1;
-                        unsigned int short_preamble:1;
                         unsigned int probe_last_frag:1;
                         struct ieee80211_hw_mode *mode;
                         struct ieee80211_rate *rate;
@@ -286,6 +285,11 @@ struct ieee80211_sub_if_data {
         unsigned int promisc:1;
         unsigned int use_protection:1; /* CTS protect ERP frames */
 
+        /* use short preamble with IEEE 802.11b: this flag is set when the AP
+         * or beacon generator reports that there are no present stations that
+         * cannot support short preambles */
+        unsigned int short_preamble:1;
+
         struct net_device_stats stats;
         int drop_unencrypted;
         int eapol; /* 0 = process EAPOL frames as normal data frames,
@@ -447,7 +451,6 @@ struct ieee80211_local {
         int fragmentation_threshold;
         int short_retry_limit; /* dot11ShortRetryLimit */
         int long_retry_limit; /* dot11LongRetryLimit */
-        int short_preamble; /* use short preamble with IEEE 802.11b */
 
         struct crypto_blkcipher *wep_tx_tfm;
         struct crypto_blkcipher *wep_rx_tfm;