feature_list: a way to pass hardware info to the kernel

Hi Sascha,
I've made the changes you suggested in this resent patch.

Everything related to custom ATAGs has been moved to the board
directory.

The generic code does not make any references to feature lists or
bootloader versions.

About the setup_feature_list prototype:
 it has been renamed to atag_appender
 it's not a function, it's a pointer to a function. Can it have a
prototype other than it's own declaration?

All non-related changes has been dropped. They were checkpatch.pl
warnings unrelated to this patch.

Regards,
  Vicente.

Signed-off-by: Vicente Bergas <vicencb@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

9 files changed, 631 insertions, 0 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index f567531d1b..6f7a71f2cb 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -152,6 +152,13 @@ config THUMB2_BAREBOX
 	  your board lowlevel init code may break in thumb-2 mode. You have been
 	  warned.
 
+config ARM_BOARD_APPEND_ATAG
+	bool "Let board specific code to add ATAGs to be passed to the kernel"
+	depends on ARM_LINUX
+	help
+	  This option is purely to start some vendor provided kernels.
+	  ** DO NOT USE FOR YOUR OWN DESIGNS! **
+
 endmenu
 
 menu "Arm specific settings"
diff --git a/arch/arm/boards/archosg9/Makefile b/arch/arm/boards/archosg9/Makefile
index 256eaf6167..450c03f2ab 100644
--- a/arch/arm/boards/archosg9/Makefile
+++ b/arch/arm/boards/archosg9/Makefile
@@ -1,3 +1,4 @@
 obj-y += board.o
+obj-$(CONFIG_ARM_BOARD_APPEND_ATAG) += archos_features.o
 obj-$(CONFIG_MACH_DO_LOWLEVEL_INIT) += lowlevel.o mux.o
 pbl-$(CONFIG_MACH_DO_LOWLEVEL_INIT) += lowlevel.o mux.o
diff --git a/arch/arm/boards/archosg9/archos_features.c b/arch/arm/boards/archosg9/archos_features.c
new file mode 100644
index 0000000000..5d934038fd
--- /dev/null
+++ b/arch/arm/boards/archosg9/archos_features.c
@@ -0,0 +1,225 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <boot.h>
+#include <asm/setup.h>
+#include "archos_features.h"
+#include "feature_list.h"
+
+static inline void *atag_data(struct tag *t)
+{
+	return ((void *)t) + sizeof(struct tag_header);
+}
+
+static struct feature_tag *features;
+
+static void setup_feature_core(void)
+{
+	features->hdr.tag = FTAG_CORE;
+	features->hdr.size = feature_tag_size(feature_tag_core);
+
+	features->u.core.magic = FEATURE_LIST_MAGIC;
+	features->u.core.list_revision = FEATURE_LIST_REV;
+	features->u.core.flags = 0;
+
+	features = feature_tag_next(features);
+}
+static void setup_feature_product_name(void)
+{
+	features->hdr.tag = FTAG_PRODUCT_NAME;
+	features->hdr.size = feature_tag_size(feature_tag_product_name);
+
+	memset(features->u.product_name.name, 0,
+		sizeof(features->u.product_name.name));
+	sprintf(features->u.product_name.name, "A80S");
+	features->u.product_name.id = 0x13A8;
+
+	features = feature_tag_next(features);
+}
+static void setup_feature_product_serial_number(void)
+{
+	features->hdr.tag = FTAG_PRODUCT_SERIAL_NUMBER;
+	features->hdr.size = feature_tag_size(feature_tag_product_serial);
+
+	features->u.product_serial.serial[0] = 0;
+	features->u.product_serial.serial[1] = 0;
+	features->u.product_serial.serial[2] = 0;
+	features->u.product_serial.serial[3] = 0;
+
+	features = feature_tag_next(features);
+}
+static void setup_feature_product_mac_address(void)
+{
+	features->hdr.tag = FTAG_PRODUCT_MAC_ADDRESS;
+	features->hdr.size = feature_tag_size(feature_tag_product_mac_address);
+
+	features->u.mac_address.addr[0] = 0;
+	features->u.mac_address.addr[1] = 0;
+	features->u.mac_address.addr[2] = 0;
+	features->u.mac_address.addr[3] = 0;
+	features->u.mac_address.addr[4] = 0;
+	features->u.mac_address.addr[5] = 0;
+	features->u.mac_address.reserved1 = 0;
+	features->u.mac_address.reserved2 = 0;
+
+	features = feature_tag_next(features);
+}
+static void setup_feature_board_pcb_revision(void)
+{
+	features->hdr.tag = FTAG_BOARD_PCB_REVISION;
+	features->hdr.size = feature_tag_size(feature_tag_board_revision);
+
+	features->u.board_revision.revision = 5;
+
+	features = feature_tag_next(features);
+}
+static void setup_feature_sdram(void)
+{
+	features->hdr.tag = FTAG_SDRAM;
+	features->hdr.size = feature_tag_size(feature_tag_sdram);
+
+	memset(features->u.sdram.vendor, 0, sizeof(features->u.sdram.vendor));
+	memset(features->u.sdram.product, 0,
+		sizeof(features->u.sdram.product));
+	sprintf(features->u.sdram.vendor , "elpida");
+	sprintf(features->u.sdram.product, "EDB8064B1PB"/*"EDB4064B2PB"*/);
+	features->u.sdram.type     = 0;
+	features->u.sdram.revision = 0;
+	features->u.sdram.flags    = 0;
+	features->u.sdram.clock    = 400;
+	features->u.sdram.param_0  = 0;
+	features->u.sdram.param_1  = 0;
+	features->u.sdram.param_2  = 0;
+	features->u.sdram.param_3  = 0;
+	features->u.sdram.param_4  = 0;
+	features->u.sdram.param_5  = 0;
+	features->u.sdram.param_6  = 0;
+	features->u.sdram.param_7  = 0;
+
+	features = feature_tag_next(features);
+}
+static void setup_feature_pmic(void)
+{
+	features->hdr.tag = FTAG_PMIC;
+	features->hdr.size = feature_tag_size(feature_tag_pmic);
+
+	features->u.pmic.flags = FTAG_PMIC_TPS62361;
+
+	features = feature_tag_next(features);
+}
+static void setup_feature_serial_port(void)
+{
+	features->hdr.tag = FTAG_SERIAL_PORT;
+	features->hdr.size = feature_tag_size(feature_tag_serial_port);
+
+	features->u.serial_port.uart_id = 1;
+	features->u.serial_port.speed = 115200;
+
+	features = feature_tag_next(features);
+}
+static void setup_feature_has_gpio_volume_keys(void)
+{
+	features->hdr.tag = FTAG_HAS_GPIO_VOLUME_KEYS;
+	features->hdr.size = feature_tag_size(feature_tag_gpio_volume_keys);
+
+	features->u.gpio_volume_keys.gpio_vol_up   = 0x2B;
+	features->u.gpio_volume_keys.gpio_vol_down = 0x2C;
+	features->u.gpio_volume_keys.flags = 0;
+
+	features = feature_tag_next(features);
+}
+static void setup_feature_screen(void)
+{
+	features->hdr.tag = FTAG_SCREEN;
+	features->hdr.size = feature_tag_size(feature_tag_screen);
+
+	memset(features->u.screen.vendor, 0,
+		sizeof(features->u.screen.vendor));
+	sprintf(features->u.screen.vendor, "CMI");
+	features->u.screen.type = 0;
+	features->u.screen.revision = 0;
+	features->u.screen.vcom = 0;
+	features->u.screen.backlight = 0xC8;
+	features->u.screen.reserved[0] = 0;
+	features->u.screen.reserved[1] = 0;
+	features->u.screen.reserved[2] = 0;
+	features->u.screen.reserved[3] = 0;
+	features->u.screen.reserved[4] = 0;
+
+	features = feature_tag_next(features);
+}
+static void setup_feature_turbo(void)
+{
+	features->hdr.tag = FTAG_TURBO;
+	features->hdr.size = feature_tag_size(feature_tag_turbo);
+
+	features->u.turbo.flag = 1;
+
+	features = feature_tag_next(features);
+}
+static void setup_feature_none(void)
+{
+	features->hdr.tag = FTAG_NONE;
+	features->hdr.size = sizeof(struct feature_tag_header) >> 2;
+
+	features = feature_tag_next(features);
+}
+static struct tag *setup_feature_list(struct tag * params)
+{
+	struct tag_feature_list *fl;
+
+	fl = atag_data(params);
+	features = (struct feature_tag *)fl->data;
+
+	setup_feature_core();
+	setup_feature_product_name();
+	setup_feature_product_serial_number();
+	setup_feature_product_mac_address();
+	setup_feature_board_pcb_revision();
+	setup_feature_sdram();
+	setup_feature_pmic();
+	setup_feature_serial_port();
+	setup_feature_has_gpio_volume_keys();
+	setup_feature_screen();
+	setup_feature_turbo();
+	setup_feature_none();
+
+	fl->size = ((u32)features) - ((u32)(fl->data));
+
+	params->hdr.tag = ATAG_FEATURE_LIST;
+	params->hdr.size = (sizeof(struct tag_feature_list) + fl->size) >> 2;
+
+	return tag_next(params);
+}
+
+static struct tag *setup_boot_version(struct tag *params)
+{
+	struct tag_boot_version *bv;
+
+	bv = atag_data(params);
+
+	params->hdr.tag = ATAG_BOOT_VERSION;
+	params->hdr.size = tag_size(tag_boot_version);
+
+	bv->major = 5;
+	bv->minor = 5;
+	bv->extra = 3;
+
+	return tag_next(params);
+}
+
+struct tag *archos_append_atags(struct tag *params)
+{
+	params = setup_feature_list(params);
+	params = setup_boot_version(params);
+	return params;
+}
diff --git a/arch/arm/boards/archosg9/archos_features.h b/arch/arm/boards/archosg9/archos_features.h
new file mode 100644
index 0000000000..5769c6c668
--- /dev/null
+++ b/arch/arm/boards/archosg9/archos_features.h
@@ -0,0 +1,22 @@
+#ifndef __ARCHOS_FEATURES_H
+#define __ARCHOS_FEATURES_H
+
+/* bootloader version */
+#define ATAG_BOOT_VERSION	0x5441000A
+
+struct tag_boot_version {
+	u32		major;
+	u32		minor;
+	u32		extra;
+};
+
+#define ATAG_FEATURE_LIST	0x5441000B
+
+struct tag_feature_list {
+	u32	size;
+	u8	data[0];
+};
+
+struct tag *archos_append_atags(struct tag * params);
+
+#endif /* __ARCHOS_FEATURES_H */
diff --git a/arch/arm/boards/archosg9/board.c b/arch/arm/boards/archosg9/board.c
index 200fe92958..8366ccafea 100644
--- a/arch/arm/boards/archosg9/board.c
+++ b/arch/arm/boards/archosg9/board.c
@@ -20,6 +20,7 @@
 #include <sizes.h>
 #include <i2c/i2c.h>
 #include <gpio.h>
+#include "archos_features.h"
 
 static int archosg9_console_init(void){
 	if (IS_ENABLED(CONFIG_DRIVER_SERIAL_OMAP4_USBBOOT))
@@ -59,6 +60,7 @@ static int archosg9_devices_init(void){
 	 */
 	armlinux_set_architecture(5032);
 	armlinux_set_revision(5);
+	armlinux_set_atag_appender(archos_append_atags);
 
 	return 0;
 }
diff --git a/arch/arm/boards/archosg9/feature_list.h b/arch/arm/boards/archosg9/feature_list.h
new file mode 100644
index 0000000000..0b726cd1a3
--- /dev/null
+++ b/arch/arm/boards/archosg9/feature_list.h
@@ -0,0 +1,352 @@
+#ifndef _FEATURE_LIST_H
+#define _FEATURE_LIST_H
+
+/*
+ This file comes from:
+ http://gitorious.org/archos/archos-gpl-gen9-kernel-ics/blobs/raw/master/
+ arch/arm/include/asm/feature_list.h
+*/
+
+#define FEATURE_LIST_MAGIC		0xFEA01234
+
+#define FEATURE_LIST_REV		0x00000001
+
+struct feature_tag_header {
+	u32 size;
+	u32 tag;
+};
+
+struct feature_tag_generic {
+	u32 vendor;
+	u32 product;
+	u32 type;
+	u32 revision;
+	u32 flags;
+};
+
+#define FTAG_NONE			0x00000000
+
+#define FTAG_CORE			0x00000001
+struct feature_tag_core {
+	u32 magic;
+	u32 list_revision;
+	u32 flags;
+};
+
+/* product specific */
+#define FTAG_PRODUCT_NAME		0x00000002
+struct feature_tag_product_name {
+	char name[64];
+	u32 id;
+};
+#define FTAG_PRODUCT_SERIAL_NUMBER	0x00000003
+struct feature_tag_product_serial {
+	u32 serial[4];
+};
+
+#define FTAG_PRODUCT_MAC_ADDRESS	0x00000004
+struct feature_tag_product_mac_address {
+	u8 addr[6];
+	u8 reserved1;
+	u8 reserved2;
+};
+
+#define FTAG_PRODUCT_OEM		0x00000005
+struct feature_tag_product_oem {
+	char name[16];
+	u32 id;
+};
+
+#define FTAG_PRODUCT_ZONE		0x00000006
+struct feature_tag_product_zone {
+	char name[16];
+	u32 id;
+};
+
+/* board pcb specific */
+#define FTAG_BOARD_PCB_REVISION		0x00000010
+struct feature_tag_board_revision {
+	u32 revision;
+};
+
+/* clock and ram setup */
+#define FTAG_CLOCK			0x00000011
+struct feature_tag_clock {
+	u32 clock;
+};
+
+#define FTAG_SDRAM			0x00000012
+struct feature_tag_sdram {
+	char vendor[16];
+	char product[32];
+	u32 type;
+	u32 revision;
+	u32 flags;
+	u32 clock;
+	/* custom params */
+	u32 param_0;
+	u32 param_1;
+	u32 param_2;
+	u32 param_3;
+	u32 param_4;
+	u32 param_5;
+	u32 param_6;
+	u32 param_7;
+};
+
+/* PMIC */
+#define FTAG_PMIC			0x00000013
+#define FTAG_PMIC_TPS62361		0x00000001
+struct feature_tag_pmic {
+	u32 flags;
+};
+
+/* serial port */
+#define FTAG_SERIAL_PORT		0x00000020
+struct feature_tag_serial_port {
+	u32 uart_id;
+	u32 speed;
+};
+
+/* turbo bit */
+#define FTAG_TURBO			0x00000014
+struct feature_tag_turbo {
+	u32 flag;
+};
+
+/*** features ****/
+#define FTAG_HAS_GPIO_VOLUME_KEYS	0x00010001
+struct feature_tag_gpio_volume_keys {
+	u32 gpio_vol_up;
+	u32 gpio_vol_down;
+	u32 flags;
+};
+
+#define FTAG_HAS_ELECTRICAL_SHORTCUT	0x00010002
+#define FTAG_HAS_DCIN			0x00010003
+struct feature_tag_dcin {
+	u32 autodetect;
+};
+
+/* external screen support */
+#define FTAG_HAS_EXT_SCREEN		0x00010004
+
+#define EXT_SCREEN_TYPE_TVOUT	0x00000001
+#define EXT_SCREEN_TYPE_HDMI	0x00000002
+#define EXT_SCREEN_TYPE_VGA	0x00000004
+struct feature_tag_ext_screen {
+	u32 type;
+	u32 revision;
+};
+
+/* wireless lan */
+#define FTAG_HAS_WIFI			0x00010005
+
+#define WIFI_TYPE_TIWLAN	0x00000001
+struct feature_tag_wifi {
+	u32 vendor;
+	u32 product;
+	u32 type;
+	u32 revision;
+	u32 flags;
+};
+
+/* bluetooth */
+#define FTAG_HAS_BLUETOOTH		0x00010006
+
+#define BLUETOOTH_TYPE_TIWLAN	0x00000001
+struct feature_tag_bluetooth {
+	u32 vendor;
+	u32 product;
+	u32 type;
+	u32 revision;
+	u32 flags;
+};
+
+/* accelerometer */
+#define FTAG_HAS_ACCELEROMETER		0x00010007
+struct feature_tag_accelerometer {
+	u32 vendor;
+	u32 product;
+	u32 type;
+	u32 revision;
+	u32 flags;
+};
+
+/* gyroscope */
+#define FTAG_HAS_GYROSCOPE		0x00010008
+
+/* compass */
+#define FTAG_HAS_COMPASS		0x00010009
+
+/* gps */
+#define FTAG_HAS_GPS			0x0001000a
+#define GPS_FLAG_DISABLED		0x00000001
+struct feature_tag_gps {
+	u32 vendor;
+	u32 product;
+	u32 revision;
+	u32 flags;
+};
+
+/* camera */
+#define FTAG_HAS_CAMERA			0x0001000b
+
+/* harddisk controller */
+#define FTAG_HAS_HARDDISK_CONTROLLER	0x0001000c
+#define HDCONTROLLER_TYPE_SATA	0x00000001
+struct feature_tag_harddisk_controller {
+	u32 vendor;
+	u32 product;
+	u32 type;
+	u32 revision;
+	u32 flags;
+};
+
+/* harddisk */
+#define FTAG_HAS_HARDDISK		0x0001000d
+
+#define HARDDISK_TYPE_SATA	0x00000001
+#define HARDDISK_TYPE_PATA	0x00000002
+struct feature_tag_harddisk {
+	u32 vendor;
+	u32 product;
+	u32 type;
+	u32 revision;
+	u32 flags;
+};
+
+/* touchscreen */
+#define FTAG_HAS_TOUCHSCREEN		0x0001000e
+
+#define TOUCHSCREEN_TYPE_CAPACITIVE 0x00000001
+#define TOUCHSCREEN_TYPE_RESISTIVE  0x00000002
+
+#define TOUCHSCREEN_FLAG_MULTITOUCH 0x00000001
+struct feature_tag_touchscreen {
+	u32 vendor;
+	u32 product;
+	u32 type;
+	u32 revision;
+	u32 flags;
+};
+
+/* microphone */
+#define FTAG_HAS_MICROPHONE		0x0001000f
+
+/* external SDMMC slot */
+#define FTAG_HAS_EXT_MMCSD_SLOT		0x00010010
+#define MMCSD_FLAG_CARDDETECT    0x00000001
+#define MMCSD_FLAG_CARDPREDETECT 0x00000002
+
+struct feature_tag_mmcsd {
+	u32 width;
+	u32 voltagemask;
+	u32 revision;
+	u32 flags;
+};
+
+/* ambient light sensor */
+#define FTAG_HAS_AMBIENT_LIGHT_SENSOR	0x00010011
+
+/* proximity sensor */
+#define FTAG_HAS_PROXIMITY_SENSOR	0x00010012
+
+/* gps */
+#define FTAG_HAS_GSM			0x00010013
+
+/* dect */
+#define FTAG_HAS_DECT			0x00010014
+
+/* hsdpa data modem */
+#define FTAG_HAS_HSDPA			0x00010015
+
+/* near field communication */
+#define FTAG_HAS_NFC			0x00010016
+
+#define FTAG_GPIO_KEYS			0x00010017
+struct feature_tag_gpio_keys {
+#define GPIO_KEYS_LONG_PRESS		0x00010000
+	u32 vol_up;
+	u32 vol_down;
+	u32 ok;
+	u32 reserved[5];
+};
+
+#define FTAG_SCREEN			0x00010018
+struct feature_tag_screen {
+	char vendor[16];
+	u32 type;
+	u32 revision;
+	u32 vcom;
+	u32 backlight;
+	u32 reserved[5];
+};
+
+#define FTAG_WIFI_PA			0x00010019
+struct feature_tag_wifi_pa {
+	char vendor[16];
+	u32 type;
+};
+
+/* loudspeaker */
+#define FTAG_HAS_SPEAKER		0x0001001a
+
+#define SPEAKER_FLAG_STEREO	 0x00000001
+#define SPEAKER_FLAG_OWN_VOLCTRL 0x00000002
+struct feature_tag_speaker {
+	u32 flags;
+};
+
+#define FTAG_BATTERY			0x0001001b
+struct feature_tag_battery {
+	u32 type;
+};
+#define BATTERY_TYPE_HIGHRS	 0x00000000
+#define BATTERY_TYPE_LOWRS	 0x00000001
+
+
+#define feature_tag_next(t) \
+	((struct feature_tag *)((u32 *)(t) + (t)->hdr.size))
+#define feature_tag_size(type) \
+	((sizeof(struct feature_tag_header) + sizeof(struct type)) >> 2)
+#define for_each_feature_tag(t, base) \
+	for (t = base; t->hdr.size; t = feature_tag_next(t))
+
+
+struct feature_tag {
+	struct feature_tag_header hdr;
+	union {
+		struct feature_tag_core			core;
+		struct feature_tag_generic		generic;
+		struct feature_tag_product_name		product_name;
+		struct feature_tag_product_serial	product_serial;
+		struct feature_tag_product_oem		product_oem;
+		struct feature_tag_product_zone		product_zone;
+		struct feature_tag_product_mac_address	mac_address;
+		struct feature_tag_board_revision	board_revision;
+		struct feature_tag_clock		clock;
+		struct feature_tag_sdram		sdram;
+		struct feature_tag_pmic			pmic;
+		struct feature_tag_turbo		turbo;
+		struct feature_tag_serial_port		serial_port;
+		struct feature_tag_gpio_volume_keys	gpio_volume_keys;
+		struct feature_tag_dcin			dcin;
+		struct feature_tag_ext_screen		ext_screen;
+		struct feature_tag_wifi			wifi;
+		struct feature_tag_bluetooth		bluetooth;
+		struct feature_tag_accelerometer	accelerometer;
+		struct feature_tag_harddisk_controller	harddisk_controller;
+		struct feature_tag_harddisk		harddisk;
+		struct feature_tag_touchscreen		touchscreen;
+		struct feature_tag_gps			gps;
+		struct feature_tag_speaker		speaker;
+		struct feature_tag_mmcsd		mmcsd;
+		struct feature_tag_gpio_keys		gpio_keys;
+		struct feature_tag_screen		screen;
+		struct feature_tag_wifi_pa		wifi_pa;
+		struct feature_tag_battery		battery;
+	} u;
+};
+
+#endif /* _FEATURE_LIST_H */
diff --git a/arch/arm/configs/archosg9_defconfig b/arch/arm/configs/archosg9_defconfig
index 2a20dd77ba..1f3d105aa0 100644
--- a/arch/arm/configs/archosg9_defconfig
+++ b/arch/arm/configs/archosg9_defconfig
@@ -11,6 +11,7 @@ CONFIG_TEXT_BASE=0xa0000000
 CONFIG_MALLOC_BASE=0x90000000
 CONFIG_MALLOC_SIZE=0x10000000
 CONFIG_KALLSYMS=y
+CONFIG_ARM_BOARD_APPEND_ATAG=y
 CONFIG_PROMPT="barebox> "
 CONFIG_LONGHELP=y
 CONFIG_GLOB=y
diff --git a/arch/arm/include/asm/armlinux.h b/arch/arm/include/asm/armlinux.h
index 8ec8c4df7c..07479fb15c 100644
--- a/arch/arm/include/asm/armlinux.h
+++ b/arch/arm/include/asm/armlinux.h
@@ -2,6 +2,7 @@
 #define __ARCH_ARMLINUX_H
 
 #include <asm/memory.h>
+#include <asm/setup.h>
 
 #if defined CONFIG_ARM_LINUX
 void armlinux_set_bootparams(void *params);
@@ -26,6 +27,14 @@ static inline void armlinux_set_serial(u64 serial)
 }
 #endif
 
+#if defined CONFIG_ARM_BOARD_APPEND_ATAG
+void armlinux_set_atag_appender(struct tag *(*)(struct tag *));
+#else
+static inline void armlinux_set_atag_appender(struct tag *(*func)(struct tag *))
+{
+}
+#endif
+
 struct image_data;
 
 void start_linux(void *adr, int swap, unsigned long initrd_address,
diff --git a/arch/arm/lib/armlinux.c b/arch/arm/lib/armlinux.c
index 9c134ed4b8..40a63ea7e1 100644
--- a/arch/arm/lib/armlinux.c
+++ b/arch/arm/lib/armlinux.c
@@ -106,6 +106,14 @@ u64 armlinux_get_serial(void)
 #endif
 }
 
+#ifdef CONFIG_ARM_BOARD_APPEND_ATAG
+static struct tag *(*atag_appender)(struct tag *);
+void armlinux_set_atag_appender(struct tag *(*func)(struct tag *))
+{
+	atag_appender = func;
+}
+#endif
+
 static void setup_start_tag(void)
 {
 	params = (struct tag *)armlinux_bootparams;
@@ -233,6 +241,10 @@ static void setup_tags(unsigned long initrd_address,
 
 	setup_revision_tag();
 	setup_serial_tag();
+#ifdef CONFIG_ARM_BOARD_APPEND_ATAG
+	if (atag_appender != NULL)
+		params = atag_appender(params);
+#endif
 	setup_end_tag();
 
 	printf("commandline: %s\n"