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Diffstat (limited to 'drivers/net/wireless/ath/hw.c')
| -rw-r--r-- | drivers/net/wireless/ath/hw.c | 126 |
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 0000000..ecc9eb0 --- /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); |
