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authorDamien Bergamini <damien@cvs.openbsd.org>2005-11-23 19:56:52 +0000
committerDamien Bergamini <damien@cvs.openbsd.org>2005-11-23 19:56:52 +0000
commit4a441ee2a14944453ba1ef83b2818ccb541e2c4d (patch)
treefc9b05908584f1ee53db50d1c82ea5216749e2e7 /sys/dev/usb
parentd66b8e9d75a34c932adf952c227220b082f408e4 (diff)
Optimize TXTIME and PLCP LENGTH field computation.
Avoid modulus operations.
Diffstat (limited to 'sys/dev/usb')
-rw-r--r--sys/dev/usb/if_ral.c41
1 files changed, 12 insertions, 29 deletions
diff --git a/sys/dev/usb/if_ral.c b/sys/dev/usb/if_ral.c
index b69cbaf3ae1..270ae7e3a2c 100644
--- a/sys/dev/usb/if_ral.c
+++ b/sys/dev/usb/if_ral.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: if_ral.c,v 1.45 2005/10/02 13:01:59 damien Exp $ */
+/* $OpenBSD: if_ral.c,v 1.46 2005/11/23 19:56:51 damien Exp $ */
/*-
* Copyright (c) 2005
@@ -1004,35 +1004,19 @@ Static uint16_t
ural_txtime(int len, int rate, uint32_t flags)
{
uint16_t txtime;
- int ceil, dbps;
if (RAL_RATE_IS_OFDM(rate)) {
- /*
- * OFDM TXTIME calculation.
- * From IEEE Std 802.11a-1999, pp. 37.
- */
- dbps = rate * 2; /* data bits per OFDM symbol */
-
- ceil = (16 + 8 * len + 6) / dbps;
- if ((16 + 8 * len + 6) % dbps != 0)
- ceil++;
-
- txtime = 16 + 4 + 4 * ceil + 6;
+ /* IEEE Std 802.11a-1999, pp. 37 */
+ txtime = (8 + 4 * len + 3 + rate - 1) / rate;
+ txtime = 16 + 4 + 4 * txtime + 6;
} else {
- /*
- * High Rate TXTIME calculation.
- * From IEEE Std 802.11b-1999, pp. 28.
- */
- ceil = (8 * len * 2) / rate;
- if ((8 * len * 2) % rate != 0)
- ceil++;
-
+ /* IEEE Std 802.11b-1999, pp. 28 */
+ txtime = (16 * len + rate - 1) / rate;
if (rate != 2 && (flags & IEEE80211_F_SHPREAMBLE))
- txtime = 72 + 24 + ceil;
+ txtime += 72 + 24;
else
- txtime = 144 + 48 + ceil;
+ txtime += 144 + 48;
}
-
return txtime;
}
@@ -1097,12 +1081,11 @@ ural_setup_tx_desc(struct ural_softc *sc, struct ural_tx_desc *desc,
* Long PLCP LENGTH field.
* From IEEE Std 802.11b-1999, pp. 16.
*/
- plcp_length = (8 * len * 2) / rate;
- remainder = (8 * len * 2) % rate;
- if (remainder != 0) {
- if (rate == 22 && (rate - remainder) / 16 != 0)
+ plcp_length = (16 * len + rate - 1) / rate;
+ if (rate == 22) {
+ remainder = (16 * len) % 22;
+ if (remainder != 0 && remainder < 7)
desc->plcp_service |= RAL_PLCP_LENGEXT;
- plcp_length++;
}
desc->plcp_length = htole16(plcp_length);
}