batman-adv: add new package

B.A.T.M.A.N. Advanced is a routing protocol for multi-hop
ad-hoc mesh networks implemented as a kernel module. It builds
against the mac80211 backport like in the routing feed.

Moved from the openwrt/routing feed, as discussed in
https://github.com/openwrt/routing/issues/184.

Signed-off-by: Josef Schlehofer <pepe.schlehofer@gmail.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

net/batman-adv/Config.in

@@ -0,0 +1,75 @@
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2007-2019  B.A.T.M.A.N. contributors:
+#
+# Marek Lindner, Simon Wunderlich
+
+#
+# B.A.T.M.A.N meshing protocol
+#
+
+config BATMAN_ADV_BATMAN_V
+	bool "B.A.T.M.A.N. V protocol"
+	depends on PACKAGE_kmod-batman-adv
+	default y
+	help
+	  This option enables the B.A.T.M.A.N. V protocol, the successor
+	  of the currently used B.A.T.M.A.N. IV protocol. The main
+	  changes include splitting of the OGM protocol into a neighbor
+	  discovery protocol (Echo Location Protocol, ELP) and a new OGM
+	  Protocol OGMv2 for flooding protocol information through the
+	  network, as well as a throughput based metric.
+	  B.A.T.M.A.N. V is currently considered experimental and not
+	  compatible to B.A.T.M.A.N. IV networks.
+
+config BATMAN_ADV_BLA
+	bool "Bridge Loop Avoidance"
+	depends on PACKAGE_kmod-batman-adv
+	select PACKAGE_kmod-lib-crc16
+	default y
+	help
+	  This option enables BLA (Bridge Loop Avoidance), a mechanism
+	  to avoid Ethernet frames looping when mesh nodes are connected
+	  to both the same LAN and the same mesh. If you will never use
+	  more than one mesh node in the same LAN, you can safely remove
+	  this feature and save some space.
+
+config BATMAN_ADV_DAT
+	bool "Distributed ARP Table"
+	depends on PACKAGE_kmod-batman-adv
+	default y
+	help
+	  This option enables DAT (Distributed ARP Table), a DHT based
+	  mechanism that increases ARP reliability on sparse wireless
+	  mesh networks. If you think that your network does not need
+	  this option you can safely remove it and save some space.
+
+config BATMAN_ADV_MCAST
+	bool "Multicast optimisation"
+	depends on PACKAGE_kmod-batman-adv
+	default y
+	help
+	  This option enables the multicast optimisation which aims to
+	  reduce the air overhead while improving the reliability of
+	  multicast messages.
+
+config BATMAN_ADV_DEBUG
+	bool "B.A.T.M.A.N. debugging"
+	depends on PACKAGE_kmod-batman-adv
+	help
+	  This is an option for use by developers; most people should
+	  say N here. This enables compilation of support for
+	  outputting debugging information to the debugfs log or tracing
+	  buffer. The output is controlled via the batadv netdev specific
+	  log_level setting.
+
+config BATMAN_ADV_TRACING
+	bool "B.A.T.M.A.N. tracing support"
+	depends on PACKAGE_kmod-batman-adv
+	select KERNEL_FTRACE
+	select KERNEL_ENABLE_DEFAULT_TRACERS
+	help
+	  This is an option for use by developers; most people should
+	  say N here. Select this option to gather traces like the debug
+	  messages using the generic tracing infrastructure of the kernel.
+	  BATMAN_ADV_DEBUG must also be selected to get trace events for
+	  batadv_dbg.

net/batman-adv/Makefile

@@ -0,0 +1,96 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+include $(TOPDIR)/rules.mk
+
+PKG_NAME:=batman-adv
+PKG_VERSION:=2026.2
+PKG_RELEASE:=1
+
+PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
+PKG_SOURCE_URL:=https://downloads.open-mesh.org/batman/releases/batman-adv-$(PKG_VERSION)
+PKG_HASH:=4e17fced2c80945e22609be87534481733ff1b5d17050de4e4f323c171418135
+PKG_EXTMOD_SUBDIRS:=net/batman-adv
+
+PKG_MAINTAINER:=Simon Wunderlich <sw@simonwunderlich.de>
+PKG_LICENSE:=GPL-2.0-only MIT
+PKG_LICENSE_FILES:=LICENSES/preferred/GPL-2.0 LICENSES/preferred/MIT
+
+PKG_BUILD_PARALLEL:=1
+
+STAMP_CONFIGURED_DEPENDS:=$(STAGING_DIR)/usr/include/mac80211-backport/backport/autoconf.h
+
+PKG_CONFIG_DEPENDS += \
+	CONFIG_BATMAN_ADV_BATMAN_V \
+	CONFIG_BATMAN_ADV_BLA \
+	CONFIG_BATMAN_ADV_DAT \
+	CONFIG_BATMAN_ADV_MCAST \
+	CONFIG_BATMAN_ADV_DEBUG \
+	CONFIG_BATMAN_ADV_TRACING
+
+include $(INCLUDE_DIR)/kernel.mk
+include $(INCLUDE_DIR)/package.mk
+
+define KernelPackage/batman-adv
+  SUBMENU:=Network Support
+  TITLE:=B.A.T.M.A.N. Adv
+  URL:=https://www.open-mesh.org/
+  DEPENDS:=+BATMAN_ADV_BLA:kmod-lib-crc16 +LINUX_6_12:kmod-lib-crc32c +kmod-cfg80211 +batctl
+  FILES:=$(PKG_BUILD_DIR)/net/batman-adv/batman-adv.$(LINUX_KMOD_SUFFIX)
+  AUTOLOAD:=$(call AutoProbe,batman-adv)
+endef
+
+define KernelPackage/batman-adv/description
+  B.A.T.M.A.N. (better approach to mobile ad-hoc networking) is
+  a routing protocol for multi-hop ad-hoc mesh networks. The
+  networks may be wired or wireless. See
+  https://www.open-mesh.org/ for more information and user space
+  tools. This package builds version $(PKG_VERSION) of the kernel
+  module.
+endef
+
+define KernelPackage/batman-adv/config
+	source "$(SOURCE)/Config.in"
+endef
+
+define Package/kmod-batman-adv/conffiles
+/etc/config/batman-adv
+endef
+
+PKG_MAKE_FLAGS:= \
+	CONFIG_BATMAN_ADV=m \
+	CONFIG_BATMAN_ADV_DEBUG=$(if $(CONFIG_BATMAN_ADV_DEBUG),y,n) \
+	CONFIG_BATMAN_ADV_BLA=$(if $(CONFIG_BATMAN_ADV_BLA),y,n) \
+	CONFIG_BATMAN_ADV_DAT=$(if $(CONFIG_BATMAN_ADV_DAT),y,n) \
+	CONFIG_BATMAN_ADV_MCAST=$(if $(CONFIG_BATMAN_ADV_MCAST),y,n) \
+	CONFIG_BATMAN_ADV_BATMAN_V=$(if $(CONFIG_BATMAN_ADV_BATMAN_V),y,n) \
+	CONFIG_BATMAN_ADV_TRACING=$(if $(CONFIG_BATMAN_ADV_TRACING),y,n) \
+
+NOSTDINC_FLAGS := \
+	$(KERNEL_NOSTDINC_FLAGS) \
+	-I$(PKG_BUILD_DIR)/include/ \
+	-I$(STAGING_DIR)/usr/include/mac80211-backport/uapi \
+	-I$(STAGING_DIR)/usr/include/mac80211-backport \
+	-I$(STAGING_DIR)/usr/include/mac80211/uapi \
+	-I$(STAGING_DIR)/usr/include/mac80211 \
+	-include backport/autoconf.h \
+	-include backport/backport.h \
+	-include $(PKG_BUILD_DIR)/compat-hacks.h \
+	-DBATADV_SOURCE_VERSION=\\\"$(PKG_VERSION)-openwrt-$(PKG_RELEASE)\\\"
+
+NOSTDINC_FLAGS += \
+	$(patsubst CONFIG_%, -DCONFIG_%=1, $(patsubst %=m,%,$(filter %=m,$(PKG_MAKE_FLAGS)))) \
+	$(patsubst CONFIG_%, -DCONFIG_%=1, $(patsubst %=y,%,$(filter %=y,$(PKG_MAKE_FLAGS)))) \
+
+define Build/Compile
+	+$(KERNEL_MAKE) $(PKG_JOBS) \
+		$(PKG_MAKE_FLAGS) \
+		M="$(PKG_BUILD_DIR)/net/batman-adv" \
+		NOSTDINC_FLAGS="$(NOSTDINC_FLAGS)" \
+		modules
+endef
+
+define KernelPackage/batman-adv/install
+	$(CP) ./files/. $(1)/
+endef
+
+$(eval $(call KernelPackage,batman-adv))

net/batman-adv/files/etc/uci-defaults/99-migrate-batadv_hardif

@@ -0,0 +1,94 @@
+#!/bin/sh
+
+# This UCI-Defaults script will split the batadv proto network interfaces
+# in batadv_hardif and batadv proto. The configuration options from
+# /etc/config/batman-adv will be moved to the latter.
+
+. /lib/functions.sh
+
+proto_batadv_to_batadv_hardif() {
+    local section="$1"
+    local proto
+    local mesh
+    local routing_algo
+
+    config_get proto "${section}" proto
+    config_get mesh "${section}" mesh
+    config_get routing_algo "${section}" routing_algo
+
+    if [ -z "$mesh" -o "${proto}" != "batadv" ]; then
+        continue
+    fi
+
+    uci set network."${section}".proto="batadv_hardif"
+    uci rename network."${section}".mesh="master"
+    uci delete network."${section}".routing_algo
+
+    # create new section or adjust existing one
+    uci set network."${mesh}"=interface
+    uci set network."${mesh}".proto=batadv
+    [ -n "${routing_algo}" ]  && uci set network."${mesh}".routing_algo="${routing_algo}"
+}
+
+mv_batadv_config_section() {
+    local section="$1"
+    local aggregated_ogms
+    local ap_isolation
+    local bonding
+    local bridge_loop_avoidance
+    local distributed_arp_table
+    local fragmentation
+    local gw_bandwidth
+    local gw_mode
+    local gw_sel_class
+    local hop_penalty
+    local isolation_mark
+    local log_level
+    local multicast_mode
+    local orig_interval
+
+    config_get aggregated_ogms "${section}" aggregated_ogms
+    config_get ap_isolation "${section}" ap_isolation
+    config_get bonding "${section}" bonding
+    config_get bridge_loop_avoidance "${section}" bridge_loop_avoidance
+    config_get distributed_arp_table "${section}" distributed_arp_table
+    config_get fragmentation "${section}" fragmentation
+    config_get gw_bandwidth "${section}" gw_bandwidth
+    config_get gw_mode "${section}" gw_mode
+    config_get gw_sel_class "${section}" gw_sel_class
+    config_get hop_penalty "${section}" hop_penalty
+    config_get isolation_mark "${section}" isolation_mark
+    config_get log_level "${section}" log_level
+    config_get multicast_mode "${section}" multicast_mode
+    config_get orig_interval "${section}" orig_interval
+
+    # update section in case it exists
+    [ -n "${aggregated_ogms}" ]  && uci set network."${section}".aggregated_ogms="${aggregated_ogms}"
+    [ -n "${ap_isolation}" ]  && uci set network."${section}".ap_isolation="${ap_isolation}"
+    [ -n "${bonding}" ]  && uci set network."${section}".bonding="${bonding}"
+    [ -n "${bridge_loop_avoidance}" ]  && uci set network."${section}".bridge_loop_avoidance="${bridge_loop_avoidance}"
+    [ -n "${distributed_arp_table}" ]  && uci set network."${section}".distributed_arp_table="${distributed_arp_table}"
+    [ -n "${fragmentation}" ]  && uci set network."${section}".fragmentation="${fragmentation}"
+    [ -n "${gw_bandwidth}" ]  && uci set network."${section}".gw_bandwidth="${gw_bandwidth}"
+    [ -n "${gw_mode}" ]  && uci set network."${section}".gw_mode="${gw_mode}"
+    [ -n "${gw_sel_class}" ]  && uci set network."${section}".gw_sel_class="${gw_sel_class}"
+    [ -n "${hop_penalty}" ]  && uci set network."${section}".hop_penalty="${hop_penalty}"
+    [ -n "${isolation_mark}" ]  && uci set network."${section}".isolation_mark="${isolation_mark}"
+    [ -n "${log_level}" ]  && uci set network."${section}".log_level="${log_level}"
+    [ -n "${multicast_mode}" ]  && uci set network."${section}".multicast_mode="${multicast_mode}"
+    [ -n "${orig_interval}" ]  && uci set network."${section}".orig_interval="${orig_interval}"
+}
+
+if [ -f /etc/config/batman-adv ]; then
+    config_load network
+    config_foreach proto_batadv_to_batadv_hardif 'interface'
+    uci commit network
+
+    config_load batman-adv
+    config_foreach mv_batadv_config_section 'mesh'
+    uci commit network
+
+    rm -f /etc/config/batman-adv
+fi
+
+exit 0

net/batman-adv/files/lib/netifd/proto/batadv.sh

@@ -0,0 +1,119 @@
+#!/bin/sh
+
+[ -n "$INCLUDE_ONLY" ] || {
+	. /lib/functions.sh
+	. ../netifd-proto.sh
+	init_proto "$@"
+}
+
+proto_batadv_init_config() {
+	no_device=1
+	available=1
+
+	proto_config_add_boolean 'aggregated_ogms:bool'
+	proto_config_add_boolean 'ap_isolation:bool'
+	proto_config_add_boolean 'bonding:bool'
+	proto_config_add_boolean 'bridge_loop_avoidance:bool'
+	proto_config_add_boolean 'distributed_arp_table:bool'
+	proto_config_add_boolean 'fragmentation:bool'
+	proto_config_add_string 'gw_bandwidth'
+	proto_config_add_string 'gw_mode'
+	proto_config_add_int 'gw_sel_class'
+	proto_config_add_int 'hop_penalty'
+	proto_config_add_string 'isolation_mark'
+	proto_config_add_string 'log_level'
+	proto_config_add_int 'multicast_fanout'
+	proto_config_add_boolean 'multicast_mode:bool'
+	proto_config_add_int 'orig_interval'
+	proto_config_add_string 'routing_algo'
+}
+
+proto_batadv_setup() {
+	local config="$1"
+	local iface="$config"
+
+	local aggregated_ogms
+	local ap_isolation
+	local bonding
+	local bridge_loop_avoidance
+	local distributed_arp_table
+	local fragmentation
+	local gw_bandwidth
+	local gw_mode
+	local gw_sel_class
+	local hop_penalty
+	local isolation_mark
+	local log_level
+	local multicast_fanout
+	local multicast_mode
+	local orig_interval
+	local routing_algo
+
+	json_get_vars aggregated_ogms
+	json_get_vars ap_isolation
+	json_get_vars bonding
+	json_get_vars bridge_loop_avoidance
+	json_get_vars distributed_arp_table
+	json_get_vars fragmentation
+	json_get_vars gw_bandwidth
+	json_get_vars gw_mode
+	json_get_vars gw_sel_class
+	json_get_vars hop_penalty
+	json_get_vars isolation_mark
+	json_get_vars log_level
+	json_get_vars multicast_fanout
+	json_get_vars multicast_mode
+	json_get_vars orig_interval
+	json_get_vars routing_algo
+
+	set_default routing_algo 'BATMAN_IV'
+
+	batctl routing_algo "$routing_algo"
+	batctl meshif "$iface" interface create
+
+	[ -n "$aggregated_ogms" ] && batctl meshif "$iface" aggregation "$aggregated_ogms"
+	[ -n "$ap_isolation" ] && batctl meshif "$iface" ap_isolation "$ap_isolation"
+	[ -n "$bonding" ] && batctl meshif "$iface" bonding "$bonding"
+	[ -n "$bridge_loop_avoidance" ] &&  batctl meshif "$iface" bridge_loop_avoidance "$bridge_loop_avoidance" 2>&-
+	[ -n "$distributed_arp_table" ] && batctl meshif "$iface" distributed_arp_table "$distributed_arp_table" 2>&-
+	[ -n "$fragmentation" ] && batctl meshif "$iface" fragmentation "$fragmentation"
+
+	case "$gw_mode" in
+	server)
+		if [ -n "$gw_bandwidth" ]; then
+			batctl meshif "$iface" gw_mode "server" "$gw_bandwidth"
+		else
+			batctl meshif "$iface" gw_mode "server"
+		fi
+		;;
+	client)
+		if [ -n "$gw_sel_class" ]; then
+			batctl meshif "$iface" gw_mode "client" "$gw_sel_class"
+		else
+			batctl meshif "$iface" gw_mode "client"
+		fi
+		;;
+	*)
+		batctl meshif "$iface" gw_mode "off"
+		;;
+	esac
+
+	[ -n "$hop_penalty" ] && batctl meshif "$iface" hop_penalty "$hop_penalty"
+	[ -n "$isolation_mark" ] && batctl meshif "$iface" isolation_mark "$isolation_mark"
+	[ -n "$multicast_fanout" ] && batctl meshif "$iface" multicast_fanout "$multicast_fanout"
+	[ -n "$multicast_mode" ] && batctl meshif "$iface" multicast_mode "$multicast_mode" 2>&-
+	[ -n "$log_level" ] && batctl meshif "$iface" loglevel "$log_level" 2>&-
+	[ -n "$orig_interval" ] && batctl meshif "$iface" orig_interval "$orig_interval"
+
+	proto_init_update "$iface" 1
+	proto_send_update "$config"
+}
+
+proto_batadv_teardown() {
+	local config="$1"
+	local iface="$config"
+
+	batctl meshif "$iface" interface destroy
+}
+
+add_protocol batadv

net/batman-adv/files/lib/netifd/proto/batadv_hardif.sh

@@ -0,0 +1,53 @@
+#!/bin/sh
+
+[ -n "$INCLUDE_ONLY" ] || {
+	. /lib/functions.sh
+	. ../netifd-proto.sh
+	init_proto "$@"
+}
+
+proto_batadv_hardif_init_config() {
+	proto_config_add_int 'elp_interval'
+	proto_config_add_int 'hop_penalty'
+	proto_config_add_string "master"
+	proto_config_add_string 'throughput_override'
+}
+
+proto_batadv_hardif_setup() {
+	local config="$1"
+	local iface="$2"
+
+	local elp_interval
+	local hop_penalty
+	local master
+	local throughput_override
+
+	json_get_vars elp_interval
+	json_get_vars hop_penalty
+	json_get_vars master
+	json_get_vars throughput_override
+
+	( proto_add_host_dependency "$config" '' "$master" )
+
+	batctl meshif "$master" interface -M add "$iface"
+
+	[ -n "$elp_interval" ] && batctl hardif "$iface" elp_interval "$elp_interval"
+	[ -n "$hop_penalty" ] && batctl hardif "$iface" hop_penalty "$hop_penalty"
+	[ -n "$throughput_override" ] && batctl hardif "$iface" throughput_override "$throughput_override"
+
+	proto_init_update "$iface" 1
+	proto_send_update "$config"
+}
+
+proto_batadv_hardif_teardown() {
+	local config="$1"
+	local iface="$2"
+
+	local master
+
+	json_get_vars master
+
+	batctl meshif "$master" interface -M del "$iface" || true
+}
+
+add_protocol batadv_hardif

net/batman-adv/files/lib/netifd/proto/batadv_vlan.sh

@@ -0,0 +1,31 @@
+#!/bin/sh
+
+[ -n "$INCLUDE_ONLY" ] || {
+	. /lib/functions.sh
+	. ../netifd-proto.sh
+	init_proto "$@"
+}
+
+proto_batadv_vlan_init_config() {
+	proto_config_add_boolean 'ap_isolation:bool'
+}
+
+proto_batadv_vlan_setup() {
+	local config="$1"
+	local iface="$2"
+
+	# batadv_vlan options
+	local ap_isolation
+
+	json_get_vars ap_isolation
+
+	batctl vlan "$iface" ap_isolation "${ap_isolation:-0}"
+	proto_init_update "$iface" 1
+	proto_send_update "$config"
+}
+
+proto_batadv_vlan_teardown() {
+	local cfg="$1"
+}
+
+add_protocol batadv_vlan

net/batman-adv/patches/0001-fix-batadv_is_cfg80211_netdev.patch

@@ -0,0 +1,20 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Alexandru Gagniuc <mr.nuke.me@gmail.com>
+Date: Thu, 6 Apr 2023 18:05:50 -0500
+Subject: fix batadv_is_cfg80211_netdev
+
+Replace CONFIG_CFG80211 with CPTCFG_CFG80211, which is the correct
+macro to use when building under backports.
+
+--- a/net/batman-adv/hard-interface.c
++++ b/net/batman-adv/hard-interface.c
+@@ -320,8 +320,7 @@ static bool batadv_is_cfg80211_netdev(st
+ {
+ 	if (!net_device)
+ 		return false;
+-
+-#if IS_ENABLED(CONFIG_CFG80211)
++#if IS_ENABLED(CPTCFG_CFG80211)
+ 	/* cfg80211 drivers have to set ieee80211_ptr */
+ 	if (net_device->ieee80211_ptr)
+ 		return true;

net/batman-adv/src/compat-hacks.h

@@ -0,0 +1,136 @@
+/* Please avoid adding hacks here - instead add it to mac80211/backports.git */
+
+#undef CONFIG_MODULE_STRIPPED
+
+#include <linux/version.h>	/* LINUX_VERSION_CODE */
+#include <linux/types.h>
+
+#if LINUX_VERSION_IS_LESS(6, 15, 0)
+#include <linux/crc32c.h>
+#endif /* LINUX_VERSION_IS_LESS(6, 15, 0) */
+
+#if LINUX_VERSION_IS_LESS(6, 16, 0)
+
+#define timer_container_of(var, callback_timer, timer_fieldname)	\
+	from_timer(var, callback_timer, timer_fieldname)
+
+#endif /* LINUX_VERSION_IS_LESS(6, 16, 0) */
+
+#if LINUX_VERSION_IS_LESS(6, 16, 0) || !defined(CONFIG_NET_CRC32C)
+
+#include <linux/skbuff.h>
+#include <linux/crc32.h>
+
+static inline u32 batadv_skb_crc32c(struct sk_buff *skb, int offset,
+				    int len, u32 crc)
+{
+	unsigned int to = offset + len;
+	unsigned int consumed = 0;
+	struct skb_seq_state st;
+	unsigned int l;
+	const u8 *data;
+
+	if (len <= 0)
+	       return crc;
+
+	skb_prepare_seq_read(skb, offset, to, &st);
+	while ((l = skb_seq_read(consumed, &data, &st)) != 0) {
+		crc = crc32c(crc, data, l);
+		consumed += l;
+	}
+
+	return crc;
+}
+
+#define skb_crc32c batadv_skb_crc32c
+
+#endif /* LINUX_VERSION_IS_LESS(6, 16, 0) || !defined(CONFIG_NET_CRC32C) */
+
+#if LINUX_VERSION_IS_LESS(7, 0, 0) && \
+    !(LINUX_VERSION_IS_GEQ(6, 18, 33) && LINUX_VERSION_IS_LESS(6, 19, 0))
+
+#define kzalloc_obj(P, GFP) \
+	kzalloc(sizeof(P), GFP)
+
+#define kmalloc_obj(P, GFP) \
+	kmalloc(sizeof(P), GFP)
+
+#define kmalloc_objs(P, COUNT, GFP) \
+	kmalloc_array((COUNT), sizeof(P), GFP)
+
+#endif /* < KERNEL_VERSION(7, 0, 0) */
+
+/* <DECLARE_EWMA> */
+
+#include <linux/version.h>
+#include_next <linux/average.h>
+
+#include <linux/bug.h>
+
+#ifdef DECLARE_EWMA
+#undef DECLARE_EWMA
+#endif /* DECLARE_EWMA */
+
+/*
+ * Exponentially weighted moving average (EWMA)
+ *
+ * This implements a fixed-precision EWMA algorithm, with both the
+ * precision and fall-off coefficient determined at compile-time
+ * and built into the generated helper funtions.
+ *
+ * The first argument to the macro is the name that will be used
+ * for the struct and helper functions.
+ *
+ * The second argument, the precision, expresses how many bits are
+ * used for the fractional part of the fixed-precision values.
+ *
+ * The third argument, the weight reciprocal, determines how the
+ * new values will be weighed vs. the old state, new values will
+ * get weight 1/weight_rcp and old values 1-1/weight_rcp. Note
+ * that this parameter must be a power of two for efficiency.
+ */
+
+#define DECLARE_EWMA(name, _precision, _weight_rcp)			\
+	struct ewma_##name {						\
+		unsigned long internal;					\
+	};								\
+	static inline void ewma_##name##_init(struct ewma_##name *e)	\
+	{								\
+		BUILD_BUG_ON(!__builtin_constant_p(_precision));	\
+		BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp));	\
+		/*							\
+		 * Even if you want to feed it just 0/1 you should have	\
+		 * some bits for the non-fractional part...		\
+		 */							\
+		BUILD_BUG_ON((_precision) > 30);			\
+		BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp);		\
+		e->internal = 0;					\
+	}								\
+	static inline unsigned long					\
+	ewma_##name##_read(struct ewma_##name *e)			\
+	{								\
+		BUILD_BUG_ON(!__builtin_constant_p(_precision));	\
+		BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp));	\
+		BUILD_BUG_ON((_precision) > 30);			\
+		BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp);		\
+		return e->internal >> (_precision);			\
+	}								\
+	static inline void ewma_##name##_add(struct ewma_##name *e,	\
+					     unsigned long val)		\
+	{								\
+		unsigned long internal = READ_ONCE(e->internal);	\
+		unsigned long weight_rcp = ilog2(_weight_rcp);		\
+		unsigned long precision = _precision;			\
+									\
+		BUILD_BUG_ON(!__builtin_constant_p(_precision));	\
+		BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp));	\
+		BUILD_BUG_ON((_precision) > 30);			\
+		BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp);		\
+									\
+		WRITE_ONCE(e->internal, internal ?			\
+			(((internal << weight_rcp) - internal) +	\
+				(val << precision)) >> weight_rcp :	\
+			(val << precision));				\
+	}
+
+/* </DECLARE_EWMA> */