kblight: Add keyboard backlight control module

This patch promotes board/nami/keyboard_backlight.c to common
directory.
Board customization is done via board_kblight_init callback.
It currently supports two drivers: direct PWM control and lm3509.

Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>

BUG=b:78360907,b:78141647
BRANCH=none
TEST=On Nami (for lm3509) and Sona (pwm), verify the followings:
1. Alt + brightness up/down works
2. After suspend-resume, brightness is restored
3. Lid close/open
4. After screen is off, keyboard backlight is turned off

Change-Id: I584c06e8702fe7b289999698f277311cfd3400bd
Reviewed-on: https://chromium-review.googlesource.com/1051027
Commit-Ready: Daisuke Nojiri <dnojiri@chromium.org>
Tested-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-by: Daisuke Nojiri <dnojiri@chromium.org>

12 files changed, 296 insertions, 289 deletions

diff --git a/board/nami/board.c b/board/nami/board.c
index af3a4d36f3..9cc93f913b 100644
--- a/board/nami/board.c
+++ b/board/nami/board.c
@@ -32,6 +32,7 @@
 #include "hooks.h"
 #include "host_command.h"
 #include "i2c.h"
+#include "keyboard_backlight.h"
 #include "keyboard_scan.h"
 #include "lid_switch.h"
 #include "math_util.h"
@@ -741,3 +742,20 @@ int board_is_lid_angle_tablet_mode(void)
 	/* Boards with no GMR sensor use lid angles to detect tablet mode. */
 	return oem == PROJECT_NAMI || oem == PROJECT_VAYNE;
 }
+
+void board_kblight_init(void)
+{
+	switch (oem) {
+	default:
+	case PROJECT_NAMI:
+	case PROJECT_VAYNE:
+	case PROJECT_PANTHEON:
+		kblight_register(&kblight_lm3509);
+		break;
+	case PROJECT_SONA:
+		if (sku == 0x3AE2)
+			break;
+		kblight_register(&kblight_pwm);
+		break;
+	}
+}
diff --git a/board/nami/board.h b/board/nami/board.h
index a292e32372..2f329e5e42 100644
--- a/board/nami/board.h
+++ b/board/nami/board.h
@@ -53,6 +53,7 @@
 #define WIRELESS_GPIO_WLAN_POWER GPIO_PP3300_DX_WLAN
 #undef CONFIG_SUPPORT_CHIP_HIBERNATION
 #define CONFIG_FANS 1
+#define CONFIG_PWM_KBLIGHT
 
 /* EC console commands */
 #define CONFIG_CMD_ACCELS
diff --git a/board/nami/build.mk b/board/nami/build.mk
index 3d83e52bfe..f4bf21113d 100644
--- a/board/nami/build.mk
+++ b/board/nami/build.mk
@@ -13,4 +13,3 @@ board-y=board.o
 board-$(CONFIG_BATTERY_SMART)+=battery.o
 board-$(CONFIG_LED_COMMON)+=led.o
 board-$(CONFIG_USB_POWER_DELIVERY)+=usb_pd_policy.o
-board-y+=keyboard_backlight.o
diff --git a/board/nami/keyboard_backlight.c b/board/nami/keyboard_backlight.c
deleted file mode 100644
index a225f96569..0000000000
--- a/board/nami/keyboard_backlight.c
+++ /dev/null
@@ -1,157 +0,0 @@
-/* Copyright 2018 The Chromium OS Authors. All rights reserved.
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- *
- * Keyboard backlight control
- */
-
-#include "console.h"
-#include "cros_board_info.h"
-#include "hooks.h"
-#include "host_command.h"
-#include "lid_switch.h"
-#include "lm3509.h"
-#include "pwm.h"
-#include "util.h"
-
-static void (*kblight_set)(int percent);
-static int (*kblight_get)(void);
-static void (*kblight_power)(int enable);
-
-/*
- * PWM routines
- */
-static void kblight_pwm_set(int percent)
-{
-	pwm_set_duty(PWM_CH_KBLIGHT, percent);
-}
-
-static int kblight_pwm_get(void)
-{
-	return pwm_get_duty(PWM_CH_KBLIGHT);
-}
-
-static void kblight_pwm_power(int enable)
-{
-	pwm_enable(PWM_CH_KBLIGHT, enable);
-}
-
-/*
- * I2C routines
- */
-static void kblight_i2c_set(int percent)
-{
-	lm3509_set_brightness(percent);
-}
-
-static int kblight_i2c_get(void)
-{
-	int percent;
-	if (lm3509_get_brightness(&percent))
-		percent = 0;
-	return percent;
-}
-
-static void kblight_i2c_power(int enable)
-{
-	lm3509_power(enable);
-}
-
-static void kblight_init(void)
-{
-	uint32_t oem = PROJECT_NAMI;
-	uint32_t sku = 0;
-
-	cbi_get_oem_id(&oem);
-	cbi_get_sku_id(&sku);
-
-	switch (oem) {
-	default:
-	case PROJECT_NAMI:
-	case PROJECT_VAYNE:
-	case PROJECT_PANTHEON:
-		kblight_set = kblight_i2c_set;
-		kblight_get = kblight_i2c_get;
-		kblight_power = kblight_i2c_power;
-		break;
-	case PROJECT_SONA:
-		if (sku == 0x3AE2)
-			break;
-		kblight_set = kblight_pwm_set;
-		kblight_get = kblight_pwm_get;
-		kblight_power = kblight_pwm_power;
-		break;
-	}
-}
-DECLARE_HOOK(HOOK_INIT, kblight_init, HOOK_PRIO_DEFAULT);
-
-static void kblight_suspend(void)
-{
-	if (kblight_power)
-		kblight_power(0);
-}
-DECLARE_HOOK(HOOK_CHIPSET_SUSPEND, kblight_suspend, HOOK_PRIO_DEFAULT);
-
-static void kblight_resume(void)
-{
-	if (kblight_power)
-		kblight_power(lid_is_open());
-}
-DECLARE_HOOK(HOOK_CHIPSET_RESUME, kblight_resume, HOOK_PRIO_DEFAULT);
-
-static void kblight_lid_change(void)
-{
-	if (kblight_power)
-		kblight_power(lid_is_open());
-}
-DECLARE_HOOK(HOOK_LID_CHANGE, kblight_lid_change, HOOK_PRIO_DEFAULT);
-
-static int hc_set_kblight(struct host_cmd_handler_args *args)
-{
-	const struct ec_params_pwm_set_keyboard_backlight *p = args->params;
-	/* Assume already enabled */
-	if (!kblight_set)
-		return EC_RES_UNAVAILABLE;
-	kblight_set(p->percent);
-	return EC_RES_SUCCESS;
-}
-DECLARE_HOST_COMMAND(EC_CMD_PWM_SET_KEYBOARD_BACKLIGHT,
-		     hc_set_kblight, EC_VER_MASK(0));
-
-static int hc_get_kblight(struct host_cmd_handler_args *args)
-{
-	struct ec_response_pwm_get_keyboard_backlight *r = args->response;
-	if (!kblight_get)
-		return EC_RES_UNAVAILABLE;
-	r->percent = kblight_get();
-	/* Assume always enabled */
-	r->enabled = 1;
-	args->response_size = sizeof(*r);
-	return EC_RES_SUCCESS;
-}
-DECLARE_HOST_COMMAND(EC_CMD_PWM_GET_KEYBOARD_BACKLIGHT,
-		     hc_get_kblight, EC_VER_MASK(0));
-
-static int cc_kblight(int argc, char **argv)
-{
-	int i;
-	char *e;
-
-	if (argc < 2) {
-		if (!kblight_get)
-			return EC_ERROR_UNIMPLEMENTED;
-		ccprintf("%d\n", kblight_get());
-		return EC_SUCCESS;
-	}
-
-	if (!kblight_set)
-		return EC_ERROR_UNIMPLEMENTED;
-	i = strtoi(argv[1], &e, 0);
-	if (*e)
-		return EC_ERROR_PARAM1;
-	kblight_set(i);
-	return EC_SUCCESS;
-}
-DECLARE_CONSOLE_COMMAND(kblight, cc_kblight,
-			"kblight [percent]",
-			"Get/set keyboard backlight brightness");
diff --git a/common/acpi.c b/common/acpi.c
index e21eb93b97..7ef3d81412 100644
--- a/common/acpi.c
+++ b/common/acpi.c
@@ -10,6 +10,7 @@
 #include "dptf.h"
 #include "hooks.h"
 #include "host_command.h"
+#include "keyboard_backlight.h"
 #include "lpc.h"
 #include "ec_commands.h"
 #include "tablet_mode.h"
@@ -147,7 +148,7 @@ int acpi_ap_to_ec(int is_cmd, uint8_t value, uint8_t *resultptr)
 			break;
 #ifdef CONFIG_PWM_KBLIGHT
 		case EC_ACPI_MEM_KEYBOARD_BACKLIGHT:
-			result = pwm_get_duty(PWM_CH_KBLIGHT);
+			result = kblight_get();
 			break;
 #endif
 #ifdef CONFIG_FANS
@@ -231,7 +232,7 @@ int acpi_ap_to_ec(int is_cmd, uint8_t value, uint8_t *resultptr)
 			 * debug console.
 			 */
 			CPRINTF("\r[%T ACPI kblight %d]", data);
-			pwm_set_duty(PWM_CH_KBLIGHT, data);
+			kblight_set(data);
 			break;
 #endif
 #ifdef CONFIG_FANS
diff --git a/common/build.mk b/common/build.mk
index 1dd7801455..1a0f27e5bf 100644
--- a/common/build.mk
+++ b/common/build.mk
@@ -87,6 +87,7 @@ common-$(CONFIG_POWER_BUTTON_X86)+=power_button_x86.o
 common-$(CONFIG_PSTORE)+=pstore_commands.o
 common-$(CONFIG_PWM)+=pwm.o
 common-$(CONFIG_PWM_KBLIGHT)+=pwm_kblight.o
+common-$(CONFIG_PWM_KBLIGHT)+=keyboard_backlight.o
 common-$(CONFIG_RMA_AUTH)+=rma_auth.o
 common-$(CONFIG_RSA)+=rsa.o
 common-$(CONFIG_ROLLBACK)+=rollback.o
diff --git a/common/keyboard_backlight.c b/common/keyboard_backlight.c
new file mode 100644
index 0000000000..d17c2bd319
--- /dev/null
+++ b/common/keyboard_backlight.c
@@ -0,0 +1,149 @@
+/* Copyright 2018 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "console.h"
+#include "ec_commands.h"
+#include "hooks.h"
+#include "host_command.h"
+#include "keyboard_backlight.h"
+#include "lid_switch.h"
+#include "timer.h"
+#include "util.h"
+
+#define CPRINTF(format, args...) cprintf(CC_KEYBOARD, format, ## args)
+#define CPRINTS(format, args...) cprints(CC_KEYBOARD, format, ## args)
+
+static struct kblight_conf kblight;
+static int current_percent;
+
+void __attribute__((weak)) board_kblight_init(void)
+{ }
+
+static int kblight_init(void)
+{
+	if (!kblight.drv || !kblight.drv->init)
+		return EC_ERROR_UNIMPLEMENTED;
+	return kblight.drv->init();
+}
+
+static void kblight_set_deferred(void)
+{
+	if (!kblight.drv || !kblight.drv->set)
+		return;
+	kblight.drv->set(current_percent);
+}
+DECLARE_DEFERRED(kblight_set_deferred);
+
+/*
+ * APIs
+ */
+int kblight_set(int percent)
+{
+	if (current_percent < 0 || 100 < current_percent)
+		return EC_ERROR_INVAL;
+	current_percent = percent;
+	/* Need to defer i2c in case it's called from an interrupt handler. */
+	hook_call_deferred(&kblight_set_deferred_data, 0);
+	return EC_SUCCESS;
+}
+
+int kblight_get(void)
+{
+	return current_percent;
+}
+
+int kblight_enable(int enable)
+{
+	if (!kblight.drv || !kblight.drv->enable)
+		return -1;
+	return kblight.drv->enable(enable);
+}
+
+int kblight_register(const struct kblight_drv *drv)
+{
+	kblight.drv = drv;
+	CPRINTS("kblight registered");
+	return EC_SUCCESS;
+}
+
+/*
+ * Hooks
+ */
+static void keyboard_backlight_init(void)
+{
+	/* Uses PWM by default. Can be customized by board_kblight_init */
+	kblight_register(&kblight_pwm);
+	board_kblight_init();
+	if (kblight_init())
+		CPRINTS("kblight init failed");
+}
+DECLARE_HOOK(HOOK_INIT, keyboard_backlight_init, HOOK_PRIO_DEFAULT);
+
+static void kblight_suspend(void)
+{
+	kblight_enable(0);
+}
+DECLARE_HOOK(HOOK_CHIPSET_SUSPEND, kblight_suspend, HOOK_PRIO_DEFAULT);
+
+static void kblight_resume(void)
+{
+	if (lid_is_open()) {
+		kblight_enable(1);
+		kblight_set(current_percent);
+	}
+}
+DECLARE_HOOK(HOOK_CHIPSET_RESUME, kblight_resume, HOOK_PRIO_DEFAULT);
+
+static void kblight_lid_change(void)
+{
+	kblight_enable(lid_is_open());
+}
+DECLARE_HOOK(HOOK_LID_CHANGE, kblight_lid_change, HOOK_PRIO_DEFAULT);
+
+/*
+ * Console and host commands
+ */
+static int cc_kblight(int argc, char **argv)
+{
+	if (argc >= 2) {
+		char *e;
+		int i = strtoi(argv[1], &e, 0);
+		if (*e)
+			return EC_ERROR_PARAM1;
+		if (kblight_set(i))
+			return EC_ERROR_PARAM1;
+	}
+	ccprintf("Keyboard backlight: %d%%\n", kblight_get());
+	return EC_SUCCESS;
+}
+DECLARE_CONSOLE_COMMAND(kblight, cc_kblight,
+			"percent",
+			"Get/set keyboard backlight");
+
+int hc_get_keyboard_backlight(struct host_cmd_handler_args *args)
+{
+	struct ec_response_pwm_get_keyboard_backlight *r = args->response;
+
+	r->percent = kblight_get();
+	r->enabled = 1;			/* Deprecated */
+	args->response_size = sizeof(*r);
+
+	return EC_RES_SUCCESS;
+}
+DECLARE_HOST_COMMAND(EC_CMD_PWM_GET_KEYBOARD_BACKLIGHT,
+		     hc_get_keyboard_backlight,
+		     EC_VER_MASK(0));
+
+int hc_set_keyboard_backlight(struct host_cmd_handler_args *args)
+{
+	const struct ec_params_pwm_set_keyboard_backlight *p = args->params;
+
+	if (kblight_set(p->percent))
+		return EC_RES_ERROR;
+	return EC_RES_SUCCESS;
+}
+DECLARE_HOST_COMMAND(EC_CMD_PWM_SET_KEYBOARD_BACKLIGHT,
+		     hc_set_keyboard_backlight,
+		     EC_VER_MASK(0));
diff --git a/common/pwm_kblight.c b/common/pwm_kblight.c
index 13415b5c51..1db5b9e5bd 100644
--- a/common/pwm_kblight.c
+++ b/common/pwm_kblight.c
@@ -3,123 +3,44 @@
  * found in the LICENSE file.
  */
 
-/* PWM control module for Chromebook keyboard backlight. */
+/* PWM control module for keyboard backlight. */
 
 #include "common.h"
-#include "console.h"
-#include "gpio.h"
-#include "hooks.h"
-#include "host_command.h"
-#include "lid_switch.h"
+#include "keyboard_backlight.h"
 #include "pwm.h"
 #include "system.h"
 #include "util.h"
 
-#define PWMKBD_SYSJUMP_TAG 0x504b  /* "PK" */
-#define PWM_HOOK_VERSION 1
-/* Saved PWM state across sysjumps */
-struct pwm_kbd_state {
-	uint8_t kblight_en;
-	uint8_t kblight_percent;
-};
-
-/*****************************************************************************/
-/* Console commands */
+const enum pwm_channel kblight_pwm_ch = PWM_CH_KBLIGHT;
 
-static int command_kblight(int argc, char **argv)
+static int kblight_pwm_set(int percent)
 {
-	if (argc >= 2) {
-		char *e;
-		int i = strtoi(argv[1], &e, 0);
-		if (*e)
-			return EC_ERROR_PARAM1;
-		pwm_set_duty(PWM_CH_KBLIGHT, i);
-	}
-
-	ccprintf("Keyboard backlight: %d%%\n", pwm_get_duty(PWM_CH_KBLIGHT));
+	pwm_set_duty(kblight_pwm_ch, percent);
 	return EC_SUCCESS;
 }
-DECLARE_CONSOLE_COMMAND(kblight, command_kblight,
-			"percent",
-			"Set keyboard backlight");
-
-/*****************************************************************************/
-/* Host commands */
-
-int pwm_command_get_keyboard_backlight(struct host_cmd_handler_args *args)
-{
-	struct ec_response_pwm_get_keyboard_backlight *r = args->response;
-
-	r->percent = pwm_get_duty(PWM_CH_KBLIGHT);
-	r->enabled = pwm_get_enabled(PWM_CH_KBLIGHT);
-	args->response_size = sizeof(*r);
-
-	return EC_RES_SUCCESS;
-}
-DECLARE_HOST_COMMAND(EC_CMD_PWM_GET_KEYBOARD_BACKLIGHT,
-		     pwm_command_get_keyboard_backlight,
-		     EC_VER_MASK(0));
-
-int pwm_command_set_keyboard_backlight(struct host_cmd_handler_args *args)
-{
-	const struct ec_params_pwm_set_keyboard_backlight *p = args->params;
-
-	pwm_set_duty(PWM_CH_KBLIGHT, p->percent);
-
-	return EC_RES_SUCCESS;
-}
-DECLARE_HOST_COMMAND(EC_CMD_PWM_SET_KEYBOARD_BACKLIGHT,
-		     pwm_command_set_keyboard_backlight,
-		     EC_VER_MASK(0));
-
-/*****************************************************************************/
-/* Hooks */
 
-static void pwm_kblight_init(void)
+static int kblight_pwm_get(void)
 {
-	const struct pwm_kbd_state *prev;
-	int version, size;
-
-	prev = (const struct pwm_kbd_state *)
-		system_get_jump_tag(PWMKBD_SYSJUMP_TAG, &version, &size);
-	if (prev && version == PWM_HOOK_VERSION && size == sizeof(*prev)) {
-		/* Restore previous state. */
-		pwm_enable(PWM_CH_KBLIGHT, prev->kblight_en);
-		pwm_set_duty(PWM_CH_KBLIGHT, prev->kblight_percent);
-	} else {
-		/* Enable keyboard backlight control, turned down */
-		pwm_set_duty(PWM_CH_KBLIGHT, 0);
-		pwm_enable(PWM_CH_KBLIGHT, 1);
-	}
+	return pwm_get_duty(kblight_pwm_ch);
 }
-DECLARE_HOOK(HOOK_INIT, pwm_kblight_init, HOOK_PRIO_DEFAULT);
 
-static void pwm_kblight_preserve_state(void)
+static int kblight_pwm_init(void)
 {
-	struct pwm_kbd_state state;
-
-	state.kblight_en = pwm_get_enabled(PWM_CH_KBLIGHT);
-	state.kblight_percent = pwm_get_duty(PWM_CH_KBLIGHT);
-
-	system_add_jump_tag(PWMKBD_SYSJUMP_TAG, PWM_HOOK_VERSION,
-			    sizeof(state), &state);
-}
-DECLARE_HOOK(HOOK_SYSJUMP, pwm_kblight_preserve_state, HOOK_PRIO_DEFAULT);
-
-static void pwm_kblight_suspend(void)
-{
-	pwm_set_duty(PWM_CH_KBLIGHT, 0);
+	/* dnojiri: Why do we need save/restore setting over sysjump? */
+	kblight_pwm_set(0);
+	pwm_enable(kblight_pwm_ch, 1);
+	return EC_SUCCESS;
 }
-DECLARE_HOOK(HOOK_CHIPSET_SUSPEND, pwm_kblight_suspend, HOOK_PRIO_DEFAULT);
 
-static void pwm_kblight_shutdown(void)
+static int kblight_pwm_enable(int enable)
 {
-	pwm_set_duty(PWM_CH_KBLIGHT, 0);
+	pwm_enable(kblight_pwm_ch, enable);
+	return EC_SUCCESS;
 }
-DECLARE_HOOK(HOOK_CHIPSET_SHUTDOWN, pwm_kblight_shutdown, HOOK_PRIO_DEFAULT);
 
-static void pwm_kblight_lid_change(void)
-{
-	pwm_enable(PWM_CH_KBLIGHT, lid_is_open());
-}
-DECLARE_HOOK(HOOK_LID_CHANGE, pwm_kblight_lid_change, HOOK_PRIO_DEFAULT);
+const struct kblight_drv kblight_pwm = {
+	.init = kblight_pwm_init,
+	.set = kblight_pwm_set,
+	.get = kblight_pwm_get,
+	.enable = kblight_pwm_enable,
+};
diff --git a/driver/led/lm3509.c b/driver/led/lm3509.c
index 58838e2bbe..4f5a911da4 100644
--- a/driver/led/lm3509.c
+++ b/driver/led/lm3509.c
@@ -7,6 +7,7 @@
 
 #include "compile_time_macros.h"
 #include "i2c.h"
+#include "keyboard_backlight.h"
 #include "lm3509.h"
 
 inline int lm3509_write(uint8_t reg, uint8_t val)
@@ -44,7 +45,7 @@ static int brightness_to_bmain(int percent)
 	return i - 1;
 }
 
-int lm3509_power(int enable)
+static int lm3509_power(int enable)
 {
 	int ret = 0;
 	uint8_t gp = 0, bmain = 0;
@@ -71,7 +72,7 @@ int lm3509_power(int enable)
 	return ret;
 }
 
-int lm3509_set_brightness(int percent)
+static int lm3509_set_brightness(int percent)
 {
 	/* We don't need to read/mask/write BMAIN because bit6 and 7 are non
 	 * functional read only bits.
@@ -79,13 +80,24 @@ int lm3509_set_brightness(int percent)
 	return lm3509_write(LM3509_REG_BMAIN, brightness_to_bmain(percent));
 }
 
-int lm3509_get_brightness(int *percent)
+static int lm3509_get_brightness(void)
 {
 	int rv, val;
 	rv = lm3509_read(LM3509_REG_BMAIN, &val);
 	if (rv)
-		return rv;
+		return -1;
 	val &= LM3509_BMAIN_MASK;
-	*percent = lm3509_brightness[val] / 10;
+	return lm3509_brightness[val] / 10;
+}
+
+static int lm3509_init(void)
+{
 	return EC_SUCCESS;
 }
+
+const struct kblight_drv kblight_lm3509 = {
+	.init = lm3509_init,
+	.set = lm3509_set_brightness,
+	.get = lm3509_get_brightness,
+	.enable = lm3509_power,
+};
diff --git a/driver/led/lm3509.h b/driver/led/lm3509.h
index 12ca480562..f1fbd6b3d4 100644
--- a/driver/led/lm3509.h
+++ b/driver/led/lm3509.h
@@ -17,28 +17,6 @@
 
 #define LM3509_BMAIN_MASK	0x1F
 
-/**
- * Power on/off and initialize LM3509.
- *
- * @param enable: 1 to enable or 0 to disable.
- * @return EC_SUCCESS or EC_ERROR_* on error.
- */
-int lm3509_power(int enable);
-
-/**
- * Set brightness level
- *
- * @param percent: Brightness level: 0 - 100%
- * @return EC_SUCCESS or EC_ERROR_* on error.
- */
-int lm3509_set_brightness(int percent);
-
-/**
- * Get current brightness level
- *
- * @param percent: Current brightness level.
- * @return EC_SUCCESS or EC_ERROR_* on error.
- */
-int lm3509_get_brightness(int *percent);
+extern const struct kblight_drv kblight_lm3509;
 
 #endif /* __CROS_EC_LM3509_H */
diff --git a/include/config.h b/include/config.h
index 6abf748912..2a7a3128cc 100644
--- a/include/config.h
+++ b/include/config.h
@@ -2268,7 +2268,12 @@
 /* Support PWM output to display backlight */
 #undef CONFIG_PWM_DISPLIGHT
 
-/* Support PWM output to keyboard backlight */
+/*
+ * Support PWM output to keyboard backlight
+ *
+ * Optionally, lm3509 can be used as a keyboard backlight controller.
+ * TODO: Create CONFIG_KEYBOARD_BACKLIGHT to allow lm3509 is used without PWM.
+ */
 #undef CONFIG_PWM_KBLIGHT
 
 /* Base address of RAM for the chip */
diff --git a/include/keyboard_backlight.h b/include/keyboard_backlight.h
new file mode 100644
index 0000000000..2389b3dfe0
--- /dev/null
+++ b/include/keyboard_backlight.h
@@ -0,0 +1,79 @@
+/* Copyright 2018 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef __CROS_EC_KEYBOARD_BACKLIGHT_H
+#define __CROS_EC_KEYBOARD_BACKLIGHT_H
+
+struct kblight_conf {
+	const struct kblight_drv *drv;
+};
+
+struct kblight_drv {
+	/**
+	 * Initialize the keyboard backlight controller
+	 * @return EC_SUCCESS or EC_ERROR_*
+	 */
+	int (*init)(void);
+
+	/**
+	 * Set the brightness
+	 * @param percent
+	 * @return EC_SUCCESS or EC_ERROR_*
+	 */
+	int (*set)(int percent);
+
+	/**
+	 * Get the current brightness
+	 * @return Brightness in percentage
+	 */
+	int (*get)(void);
+
+	/**
+	 * Enable or disable keyboard backlight
+	 * @param enable: 1=Enable, 0=Disable.
+	 * @return EC_SUCCESS or EC_ERROR_*
+	 */
+	int (*enable)(int enable);
+};
+
+/**
+ * Initialize keyboard backlight per board
+ */
+void board_kblight_init(void);
+
+/**
+ * Set keyboard backlight brightness
+ *
+ * @param percent Brightness in percentage
+ * @return EC_SUCCESS or EC_ERROR_*
+ */
+int kblight_set(int percent);
+
+/**
+ * Get keyboard backlight brightness
+ *
+ * @return Brightness in percentage
+ */
+int kblight_get(void);
+
+/**
+ * Enable or disable keyboard backlight
+ *
+ * @param enable: 1=Enable, 0=Disable.
+ * @return EC_SUCCESS or EC_ERROR_*
+ */
+int kblight_enable(int enable);
+
+/**
+ * Register keyboard backlight controller
+ *
+ * @param drv: Driver of keyboard backlight controller
+ * @return EC_SUCCESS or EC_ERROR_*
+ */
+int kblight_register(const struct kblight_drv *drv);
+
+extern const struct kblight_drv kblight_pwm;
+
+#endif /* __CROS_EC_KEYBOARD_BACKLIGHT_H */