mac80211: add PID controller based rate control algorithm
Add a new rate control algorithm based on a PID controller. It samples the percentage of failed frames over time, feeds the result into the controller and uses its output to control the TX rate. Signed-off-by: Mattias Nissler <mattias.nissler@gmx.de> Signed-off-by: John W. Linville <linville@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Mattias Nissler
David S. Miller
parent
1abbe498e4
commit
ad01837593
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@ -25,6 +25,18 @@ config MAC80211_RCSIMPLE
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Say Y unless you know you will have another algorithm
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available.
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config MAC80211_RCPID
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bool "'PID' rate control algorithm" if EMBEDDED
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default y
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depends on MAC80211
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help
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This option enables a TX rate control algorithm for
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mac80211 that uses a PID controller to select the TX
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rate.
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Say Y unless you're sure you want to use a different
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rate control algorithm.
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config MAC80211_LEDS
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bool "Enable LED triggers"
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depends on MAC80211 && LEDS_TRIGGERS
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@ -4,6 +4,7 @@ mac80211-objs-$(CONFIG_MAC80211_LEDS) += ieee80211_led.o
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mac80211-objs-$(CONFIG_MAC80211_DEBUGFS) += debugfs.o debugfs_sta.o debugfs_netdev.o debugfs_key.o
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mac80211-objs-$(CONFIG_NET_SCHED) += wme.o
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mac80211-objs-$(CONFIG_MAC80211_RCSIMPLE) += rc80211_simple.o
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mac80211-objs-$(CONFIG_MAC80211_RCPID) += rc80211_pid.o
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mac80211-objs := \
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ieee80211.o \
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@ -1315,23 +1315,37 @@ static int __init ieee80211_init(void)
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#ifdef CONFIG_MAC80211_RCSIMPLE
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ret = ieee80211_rate_control_register(&mac80211_rcsimple);
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if (ret)
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return ret;
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goto fail;
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#endif
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#ifdef CONFIG_MAC80211_RCPID
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ret = ieee80211_rate_control_register(&mac80211_rcpid);
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if (ret)
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goto fail;
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#endif
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ret = ieee80211_wme_register();
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if (ret) {
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#ifdef CONFIG_MAC80211_RCSIMPLE
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ieee80211_rate_control_unregister(&mac80211_rcsimple);
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#endif
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printk(KERN_DEBUG "ieee80211_init: failed to "
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"initialize WME (err=%d)\n", ret);
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return ret;
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goto fail;
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}
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ieee80211_debugfs_netdev_init();
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ieee80211_regdomain_init();
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return 0;
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fail:
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#ifdef CONFIG_MAC80211_RCSIMPLE
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ieee80211_rate_control_unregister(&mac80211_rcsimple);
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#endif
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#ifdef CONFIG_MAC80211_RCPID
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ieee80211_rate_control_unregister(&mac80211_rcpid);
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#endif
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return ret;
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}
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static void __exit ieee80211_exit(void)
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@ -1339,6 +1353,9 @@ static void __exit ieee80211_exit(void)
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#ifdef CONFIG_MAC80211_RCSIMPLE
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ieee80211_rate_control_unregister(&mac80211_rcsimple);
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#endif
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#ifdef CONFIG_MAC80211_RCPID
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ieee80211_rate_control_unregister(&mac80211_rcpid);
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#endif
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ieee80211_wme_unregister();
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ieee80211_debugfs_netdev_exit();
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@ -61,6 +61,9 @@ struct rate_control_ref {
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/* default 'simple' algorithm */
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extern struct rate_control_ops mac80211_rcsimple;
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/* 'PID' algorithm */
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extern struct rate_control_ops mac80211_rcpid;
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int ieee80211_rate_control_register(struct rate_control_ops *ops);
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void ieee80211_rate_control_unregister(struct rate_control_ops *ops);
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@ -0,0 +1,365 @@
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/*
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* Copyright 2002-2005, Instant802 Networks, Inc.
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* Copyright 2005, Devicescape Software, Inc.
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* Copyright 2007, Mattias Nissler <mattias.nissler@gmx.de>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/netdevice.h>
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#include <linux/types.h>
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#include <linux/skbuff.h>
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#include <net/mac80211.h>
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#include "ieee80211_rate.h"
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/* This is an implementation of a TX rate control algorithm that uses a PID
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* controller. Given a target failed frames rate, the controller decides about
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* TX rate changes to meet the target failed frames rate.
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*
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* The controller basically computes the following:
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*
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* adj = CP * err + CI * err_avg + CD * (err - last_err)
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*
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* where
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* adj adjustment value that is used to switch TX rate (see below)
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* err current error: target vs. current failed frames percentage
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* last_err last error
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* err_avg average (i.e. poor man's integral) of recent errors
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* CP Proportional coefficient
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* CI Integral coefficient
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* CD Derivative coefficient
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*
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* CP, CI, CD are subject to careful tuning.
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*
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* The integral component uses a exponential moving average approach instead of
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* an actual sliding window. The advantage is that we don't need to keep an
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* array of the last N error values and computation is easier.
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*
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* Once we have the adj value, we need to map it to a TX rate to be selected.
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* For now, we depend on the rates to be ordered in a way such that more robust
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* rates (i.e. such that exhibit a lower framed failed percentage) come first.
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* E.g. for the 802.11b/g case, we first have the b rates in ascending order,
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* then the g rates. The adj simply decides the index of the TX rate in the list
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* to switch to (relative to the current TX rate entry).
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*
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* Note that for the computations we use a fixed-point representation to avoid
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* floating point arithmetic. Hence, all values are shifted left by
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* RC_PID_ARITH_SHIFT.
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*/
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/* Sampling period for measuring percentage of failed frames. */
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#define RC_PID_INTERVAL (HZ / 8)
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/* Exponential averaging smoothness (used for I part of PID controller) */
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#define RC_PID_SMOOTHING_SHIFT 3
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#define RC_PID_SMOOTHING (1 << RC_PID_SMOOTHING_SHIFT)
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/* Fixed point arithmetic shifting amount. */
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#define RC_PID_ARITH_SHIFT 8
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/* Fixed point arithmetic factor. */
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#define RC_PID_ARITH_FACTOR (1 << RC_PID_ARITH_SHIFT)
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/* Proportional PID component coefficient. */
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#define RC_PID_COEFF_P 15
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/* Integral PID component coefficient. */
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#define RC_PID_COEFF_I 9
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/* Derivative PID component coefficient. */
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#define RC_PID_COEFF_D 15
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/* Target failed frames rate for the PID controller. NB: This effectively gives
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* maximum failed frames percentage we're willing to accept. If the wireless
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* link quality is good, the controller will fail to adjust failed frames
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* percentage to the target. This is intentional.
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*/
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#define RC_PID_TARGET_PF (11 << RC_PID_ARITH_SHIFT)
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struct rc_pid_sta_info {
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unsigned long last_change;
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unsigned long last_sample;
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u32 tx_num_failed;
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u32 tx_num_xmit;
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/* Average failed frames percentage error (i.e. actual vs. target
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* percentage), scaled by RC_PID_SMOOTHING. This value is computed
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* using using an exponential weighted average technique:
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*
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* (RC_PID_SMOOTHING - 1) * err_avg_old + err
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* err_avg = ------------------------------------------
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* RC_PID_SMOOTHING
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*
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* where err_avg is the new approximation, err_avg_old the previous one
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* and err is the error w.r.t. to the current failed frames percentage
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* sample. Note that the bigger RC_PID_SMOOTHING the more weight is
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* given to the previous estimate, resulting in smoother behavior (i.e.
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* corresponding to a longer integration window).
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*
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* For computation, we actually don't use the above formula, but this
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* one:
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*
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* err_avg_scaled = err_avg_old_scaled - err_avg_old + err
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*
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* where:
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* err_avg_scaled = err * RC_PID_SMOOTHING
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* err_avg_old_scaled = err_avg_old * RC_PID_SMOOTHING
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*
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* This avoids floating point numbers and the per_failed_old value can
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* easily be obtained by shifting per_failed_old_scaled right by
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* RC_PID_SMOOTHING_SHIFT.
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*/
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s32 err_avg_sc;
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/* Last framed failes percentage sample */
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u32 last_pf;
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};
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/* Algorithm parameters. We keep them on a per-algorithm approach, so they can
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* be tuned individually for each interface.
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*/
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struct rc_pid_info {
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/* The failed frames percentage target. */
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u32 target;
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/* P, I and D coefficients. */
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s32 coeff_p;
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s32 coeff_i;
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s32 coeff_d;
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};
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static void rate_control_pid_adjust_rate(struct ieee80211_local *local,
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struct sta_info *sta, int adj)
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{
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struct ieee80211_sub_if_data *sdata;
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struct ieee80211_hw_mode *mode;
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int newidx = sta->txrate + adj;
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int maxrate;
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int back = (adj > 0) ? 1 : -1;
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sdata = IEEE80211_DEV_TO_SUB_IF(sta->dev);
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if (sdata->bss && sdata->bss->force_unicast_rateidx > -1) {
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/* forced unicast rate - do not change STA rate */
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return;
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}
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mode = local->oper_hw_mode;
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maxrate = sdata->bss ? sdata->bss->max_ratectrl_rateidx : -1;
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if (newidx < 0)
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newidx = 0;
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else if (newidx >= mode->num_rates)
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newidx = mode->num_rates - 1;
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while (newidx != sta->txrate) {
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if (rate_supported(sta, mode, newidx) &&
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(maxrate < 0 || newidx <= maxrate)) {
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sta->txrate = newidx;
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break;
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}
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newidx += back;
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}
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}
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static void rate_control_pid_sample(struct rc_pid_info *pinfo,
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struct ieee80211_local *local,
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struct sta_info *sta)
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{
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struct rc_pid_sta_info *spinfo = sta->rate_ctrl_priv;
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u32 pf;
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s32 err_avg;
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s32 err_prop;
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s32 err_int;
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s32 err_der;
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int adj;
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spinfo = sta->rate_ctrl_priv;
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spinfo->last_sample = jiffies;
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/* If no frames were transmitted, we assume the old sample is
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* still a good measurement and copy it. */
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if (spinfo->tx_num_xmit == 0)
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pf = spinfo->last_pf;
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else {
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pf = spinfo->tx_num_failed * 100 / spinfo->tx_num_xmit;
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pf <<= RC_PID_ARITH_SHIFT;
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spinfo->tx_num_xmit = 0;
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spinfo->tx_num_failed = 0;
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}
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/* Compute the proportional, integral and derivative errors. */
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err_prop = RC_PID_TARGET_PF - pf;
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err_avg = spinfo->err_avg_sc >> RC_PID_SMOOTHING_SHIFT;
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spinfo->err_avg_sc = spinfo->err_avg_sc - err_avg + err_prop;
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err_int = spinfo->err_avg_sc >> RC_PID_SMOOTHING_SHIFT;
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err_der = pf - spinfo->last_pf;
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spinfo->last_pf = pf;
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/* Compute the controller output. */
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adj = (err_prop * pinfo->coeff_p + err_int * pinfo->coeff_i
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+ err_der * pinfo->coeff_d);
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/* We need to do an arithmetic right shift. ISO C says this is
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* implementation defined for negative left operands. Hence, be
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* careful to get it right, also for negative values. */
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adj = (adj < 0) ? -((-adj) >> (2 * RC_PID_ARITH_SHIFT)) :
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adj >> (2 * RC_PID_ARITH_SHIFT);
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/* Change rate. */
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if (adj)
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rate_control_pid_adjust_rate(local, sta, adj);
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}
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static void rate_control_pid_tx_status(void *priv, struct net_device *dev,
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struct sk_buff *skb,
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struct ieee80211_tx_status *status)
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{
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struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
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struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
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struct rc_pid_info *pinfo = priv;
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struct sta_info *sta;
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struct rc_pid_sta_info *spinfo;
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sta = sta_info_get(local, hdr->addr1);
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if (!sta)
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return;
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/* Ignore all frames that were sent with a different rate than the rate
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* we currently advise mac80211 to use. */
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if (status->control.rate != &local->oper_hw_mode->rates[sta->txrate])
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return;
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spinfo = sta->rate_ctrl_priv;
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spinfo->tx_num_xmit++;
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/* We count frames that totally failed to be transmitted as two bad
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* frames, those that made it out but had some retries as one good and
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* one bad frame. */
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if (status->excessive_retries) {
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spinfo->tx_num_failed += 2;
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spinfo->tx_num_xmit++;
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} else if (status->retry_count) {
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spinfo->tx_num_failed++;
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spinfo->tx_num_xmit++;
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}
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if (status->excessive_retries) {
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sta->tx_retry_failed++;
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sta->tx_num_consecutive_failures++;
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sta->tx_num_mpdu_fail++;
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} else {
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sta->last_ack_rssi[0] = sta->last_ack_rssi[1];
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sta->last_ack_rssi[1] = sta->last_ack_rssi[2];
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sta->last_ack_rssi[2] = status->ack_signal;
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sta->tx_num_consecutive_failures = 0;
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sta->tx_num_mpdu_ok++;
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}
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sta->tx_retry_count += status->retry_count;
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sta->tx_num_mpdu_fail += status->retry_count;
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/* Update PID controller state. */
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if (time_after(jiffies, spinfo->last_sample + RC_PID_INTERVAL))
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rate_control_pid_sample(pinfo, local, sta);
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sta_info_put(sta);
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}
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static void rate_control_pid_get_rate(void *priv, struct net_device *dev,
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struct ieee80211_hw_mode *mode,
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struct sk_buff *skb,
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struct rate_selection *sel)
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{
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struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
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struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
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struct sta_info *sta;
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int rateidx;
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sta = sta_info_get(local, hdr->addr1);
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if (!sta) {
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sel->rate = rate_lowest(local, mode, NULL);
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sta_info_put(sta);
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return;
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}
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rateidx = sta->txrate;
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if (rateidx >= mode->num_rates)
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rateidx = mode->num_rates - 1;
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sta_info_put(sta);
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sel->rate = &mode->rates[rateidx];
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}
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static void rate_control_pid_rate_init(void *priv, void *priv_sta,
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struct ieee80211_local *local,
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struct sta_info *sta)
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{
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/* TODO: This routine should consider using RSSI from previous packets
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* as we need to have IEEE 802.1X auth succeed immediately after assoc..
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* Until that method is implemented, we will use the lowest supported
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* rate as a workaround. */
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sta->txrate = rate_lowest_index(local, local->oper_hw_mode, sta);
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}
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static void *rate_control_pid_alloc(struct ieee80211_local *local)
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{
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struct rc_pid_info *pinfo;
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pinfo = kmalloc(sizeof(*pinfo), GFP_ATOMIC);
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pinfo->target = RC_PID_TARGET_PF;
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pinfo->coeff_p = RC_PID_COEFF_P;
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pinfo->coeff_i = RC_PID_COEFF_I;
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pinfo->coeff_d = RC_PID_COEFF_D;
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return pinfo;
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}
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static void rate_control_pid_free(void *priv)
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{
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struct rc_pid_info *pinfo = priv;
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kfree(pinfo);
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}
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static void rate_control_pid_clear(void *priv)
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{
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}
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static void *rate_control_pid_alloc_sta(void *priv, gfp_t gfp)
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{
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struct rc_pid_sta_info *spinfo;
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spinfo = kzalloc(sizeof(*spinfo), gfp);
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return spinfo;
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}
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static void rate_control_pid_free_sta(void *priv, void *priv_sta)
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{
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struct rc_pid_sta_info *spinfo = priv_sta;
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kfree(spinfo);
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}
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struct rate_control_ops mac80211_rcpid = {
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.name = "pid",
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.tx_status = rate_control_pid_tx_status,
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.get_rate = rate_control_pid_get_rate,
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.rate_init = rate_control_pid_rate_init,
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.clear = rate_control_pid_clear,
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.alloc = rate_control_pid_alloc,
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.free = rate_control_pid_free,
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.alloc_sta = rate_control_pid_alloc_sta,
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.free_sta = rate_control_pid_free_sta,
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};
|
||||
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Reference in New Issue