1 files changed, 126 insertions, 0 deletions

diff --git a/drivers/net/wireless/ath/hw.c b/drivers/net/wireless/ath/hw.c
new file mode 100644
index 000000000000..ecc9eb01f4fa
--- /dev/null
+++ b/drivers/net/wireless/ath/hw.c
@@ -0,0 +1,126 @@
+/*
+ * Copyright (c) 2009 Atheros Communications Inc.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <asm/unaligned.h>
+
+#include "ath.h"
+#include "reg.h"
+
+#define REG_READ        common->ops->read
+#define REG_WRITE       common->ops->write
+
+/**
+ * ath_hw_set_bssid_mask - filter out bssids we listen
+ *
+ * @common: the ath_common struct for the device.
+ *
+ * BSSID masking is a method used by AR5212 and newer hardware to inform PCU
+ * which bits of the interface's MAC address should be looked at when trying
+ * to decide which packets to ACK. In station mode and AP mode with a single
+ * BSS every bit matters since we lock to only one BSS. In AP mode with
+ * multiple BSSes (virtual interfaces) not every bit matters because hw must
+ * accept frames for all BSSes and so we tweak some bits of our mac address
+ * in order to have multiple BSSes.
+ *
+ * NOTE: This is a simple filter and does *not* filter out all
+ * relevant frames. Some frames that are not for us might get ACKed from us
+ * by PCU because they just match the mask.
+ *
+ * When handling multiple BSSes you can get the BSSID mask by computing the
+ * set of  ~ ( MAC XOR BSSID ) for all bssids we handle.
+ *
+ * When you do this you are essentially computing the common bits of all your
+ * BSSes. Later it is assumed the harware will "and" (&) the BSSID mask with
+ * the MAC address to obtain the relevant bits and compare the result with
+ * (frame's BSSID & mask) to see if they match.
+ *
+ * Simple example: on your card you have have two BSSes you have created with
+ * BSSID-01 and BSSID-02. Lets assume BSSID-01 will not use the MAC address.
+ * There is another BSSID-03 but you are not part of it. For simplicity's sake,
+ * assuming only 4 bits for a mac address and for BSSIDs you can then have:
+ *
+ *                  \
+ * MAC:        0001 |
+ * BSSID-01:   0100 | --> Belongs to us
+ * BSSID-02:   1001 |
+ *                  /
+ * -------------------
+ * BSSID-03:   0110  | --> External
+ * -------------------
+ *
+ * Our bssid_mask would then be:
+ *
+ *             On loop iteration for BSSID-01:
+ *             ~(0001 ^ 0100)  -> ~(0101)
+ *                             ->   1010
+ *             bssid_mask      =    1010
+ *
+ *             On loop iteration for BSSID-02:
+ *             bssid_mask &= ~(0001   ^   1001)
+ *             bssid_mask =   (1010)  & ~(0001 ^ 1001)
+ *             bssid_mask =   (1010)  & ~(1001)
+ *             bssid_mask =   (1010)  &  (0110)
+ *             bssid_mask =   0010
+ *
+ * A bssid_mask of 0010 means "only pay attention to the second least
+ * significant bit". This is because its the only bit common
+ * amongst the MAC and all BSSIDs we support. To findout what the real
+ * common bit is we can simply "&" the bssid_mask now with any BSSID we have
+ * or our MAC address (we assume the hardware uses the MAC address).
+ *
+ * Now, suppose there's an incoming frame for BSSID-03:
+ *
+ * IFRAME-01:  0110
+ *
+ * An easy eye-inspeciton of this already should tell you that this frame
+ * will not pass our check. This is beacuse the bssid_mask tells the
+ * hardware to only look at the second least significant bit and the
+ * common bit amongst the MAC and BSSIDs is 0, this frame has the 2nd LSB
+ * as 1, which does not match 0.
+ *
+ * So with IFRAME-01 we *assume* the hardware will do:
+ *
+ *     allow = (IFRAME-01 & bssid_mask) == (bssid_mask & MAC) ? 1 : 0;
+ *  --> allow = (0110 & 0010) == (0010 & 0001) ? 1 : 0;
+ *  --> allow = (0010) == 0000 ? 1 : 0;
+ *  --> allow = 0
+ *
+ *  Lets now test a frame that should work:
+ *
+ * IFRAME-02:  0001 (we should allow)
+ *
+ *     allow = (0001 & 1010) == 1010
+ *
+ *     allow = (IFRAME-02 & bssid_mask) == (bssid_mask & MAC) ? 1 : 0;
+ *  --> allow = (0001 & 0010) ==  (0010 & 0001) ? 1 :0;
+ *  --> allow = (0010) == (0010)
+ *  --> allow = 1
+ *
+ * Other examples:
+ *
+ * IFRAME-03:  0100 --> allowed
+ * IFRAME-04:  1001 --> allowed
+ * IFRAME-05:  1101 --> allowed but its not for us!!!
+ *
+ */
+void ath_hw_setbssidmask(struct ath_common *common)
+{
+        void *ah = common->ah;
+
+        REG_WRITE(ah, get_unaligned_le32(common->bssidmask), AR_BSSMSKL);
+        REG_WRITE(ah, get_unaligned_le16(common->bssidmask + 4), AR_BSSMSKU);
+}
+EXPORT_SYMBOL(ath_hw_setbssidmask);