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authorBruno Randolf <br1@einfach.org>2010-11-10 12:50:50 +0900
committerJohn W. Linville <linville@tuxdriver.com>2010-11-16 16:37:05 -0500
commitafe0cbf87500f0585d217deb8c6fd329793a7957 (patch)
treea7e4f6db468e623961ab2b71ccf2bfb9c6756894 /include/linux/nl80211.h
parent0e67d6cb753643fc076a90fa9309301b3fbfb8db (diff)
cfg80211: Add nl80211 antenna configuration
Allow setting of TX and RX antennas configuration via nl80211. The antenna configuration is defined as a bitmap of allowed antennas to use. This API can be used to mask out antennas which are not attached or should not be used for other reasons like regulatory concerns or special setups. Separate bitmaps are used for RX and TX to allow configuring different antennas for receiving and transmitting. Each bitmap is 32 bit long, each bit representing one antenna, starting with antenna 1 at the first bit. If an antenna bit is set, this means the driver is allowed to use this antenna for RX or TX respectively; if the bit is not set the hardware is not allowed to use this antenna. Using bitmaps has the benefit of allowing for a flexible configuration interface which can support many different configurations and which can be used for 802.11n as well as non-802.11n devices. Instead of relying on some hardware specific assumptions, drivers can use this information to know which antennas are actually attached to the system and derive their capabilities based on that. 802.11n devices should enable or disable chains, based on which antennas are present (If all antennas belonging to a particular chain are disabled, the entire chain should be disabled). HT capabilities (like STBC, TX Beamforming, Antenna selection) should be calculated based on the available chains after applying the antenna masks. Should a 802.11n device have diversity antennas attached to one of their chains, diversity can be enabled or disabled based on the antenna information. Non-802.11n drivers can use the antenna masks to select RX and TX antennas and to enable or disable antenna diversity. While covering chainmasks for 802.11n and the standard "legacy" modes "fixed antenna 1", "fixed antenna 2" and "diversity" this API also allows more rare, but useful configurations as follows: 1) Send on antenna 1, receive on antenna 2 (or vice versa). This can be used to have a low gain antenna for TX in order to keep within the regulatory constraints and a high gain antenna for RX in order to receive weaker signals ("speak softly, but listen harder"). This can be useful for building long-shot outdoor links. Another usage of this setup is having a low-noise pre-amplifier on antenna 1 and a power amplifier on the other antenna. This way transmit noise is mostly kept out of the low noise receive channel. (This would be bitmaps: tx 1 rx 2). 2) Another similar setup is: Use RX diversity on both antennas, but always send on antenna 1. Again that would allow us to benefit from a higher gain RX antenna, while staying within the legal limits. (This would be: tx 0 rx 3). 3) And finally there can be special experimental setups in research and development even with pre 802.11n hardware where more than 2 antennas are available. It's good to keep the API simple, yet flexible. Signed-off-by: Bruno Randolf <br1@einfach.org> -- v7: Made bitmasks 32 bit wide and rebased to latest wireless-testing. Signed-off-by: John W. Linville <linville@tuxdriver.com>
Diffstat (limited to 'include/linux/nl80211.h')
-rw-r--r--include/linux/nl80211.h25
1 files changed, 25 insertions, 0 deletions
diff --git a/include/linux/nl80211.h b/include/linux/nl80211.h
index fb877b5621b..17c5c884925 100644
--- a/include/linux/nl80211.h
+++ b/include/linux/nl80211.h
@@ -804,6 +804,28 @@ enum nl80211_commands {
* @NL80211_ATTR_SUPPORT_IBSS_RSN: The device supports IBSS RSN, which mostly
* means support for per-station GTKs.
*
+ * @NL80211_ATTR_WIPHY_ANTENNA_TX: Bitmap of allowed antennas for transmitting.
+ * This can be used to mask out antennas which are not attached or should
+ * not be used for transmitting. If an antenna is not selected in this
+ * bitmap the hardware is not allowed to transmit on this antenna.
+ *
+ * Each bit represents one antenna, starting with antenna 1 at the first
+ * bit. Depending on which antennas are selected in the bitmap, 802.11n
+ * drivers can derive which chainmasks to use (if all antennas belonging to
+ * a particular chain are disabled this chain should be disabled) and if
+ * a chain has diversity antennas wether diversity should be used or not.
+ * HT capabilities (STBC, TX Beamforming, Antenna selection) can be
+ * derived from the available chains after applying the antenna mask.
+ * Non-802.11n drivers can derive wether to use diversity or not.
+ * Drivers may reject configurations or RX/TX mask combinations they cannot
+ * support by returning -EINVAL.
+ *
+ * @NL80211_ATTR_WIPHY_ANTENNA_RX: Bitmap of allowed antennas for receiving.
+ * This can be used to mask out antennas which are not attached or should
+ * not be used for receiving. If an antenna is not selected in this bitmap
+ * the hardware should not be configured to receive on this antenna.
+ * For a more detailed descripton see @NL80211_ATTR_WIPHY_ANTENNA_TX.
+ *
* @NL80211_ATTR_MAX: highest attribute number currently defined
* @__NL80211_ATTR_AFTER_LAST: internal use
*/
@@ -973,6 +995,9 @@ enum nl80211_attrs {
NL80211_ATTR_SUPPORT_IBSS_RSN,
+ NL80211_ATTR_WIPHY_ANTENNA_TX,
+ NL80211_ATTR_WIPHY_ANTENNA_RX,
+
/* add attributes here, update the policy in nl80211.c */
__NL80211_ATTR_AFTER_LAST,