diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index a9e60464df74c0e0f6dac34b9a8b1d269299f7bb..b032808d9c1447f3d3102025976f073fe238aefa 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -3,7 +3,7 @@
 # Direct Rendering Infrastructure (DRI) in XFree86 4.1.0 and higher.
 
 ccflags-y := -Iinclude/drm
-i915-y := i915_drv.o i915_dma.o i915_irq.o i915_mem.o
+i915-y := i915_drv.o i915_dma.o i915_irq.o i915_mem.o i915_opregion.o
 
 i915-$(CONFIG_COMPAT)   += i915_ioc32.o
 
diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index f1b5aa92fa83ad427fc4249844ed88a191635690..29115450ee460abcc0bcae27612c3d4744e7c0b4 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -810,6 +810,8 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 	if (!IS_I945G(dev) && !IS_I945GM(dev))
 		pci_enable_msi(dev->pdev);
 
+	intel_opregion_init(dev);
+
 	spin_lock_init(&dev_priv->user_irq_lock);
 
 	return ret;
@@ -827,6 +829,8 @@ int i915_driver_unload(struct drm_device *dev)
 	if (dev_priv->mmio_map)
 		drm_rmmap(dev, dev_priv->mmio_map);
 
+	intel_opregion_free(dev);
+
 	drm_free(dev->dev_private, sizeof(drm_i915_private_t),
 		 DRM_MEM_DRIVER);
 
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 6c99aab12da39f03a276155c10e59af0bcefd977..d95eca2bc454fb0e67622e7975e2faff421c0735 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -371,6 +371,8 @@ static int i915_suspend(struct drm_device *dev, pm_message_t state)
 
 	i915_save_vga(dev);
 
+	intel_opregion_free(dev);
+
 	if (state.event == PM_EVENT_SUSPEND) {
 		/* Shut down the device */
 		pci_disable_device(dev->pdev);
@@ -532,6 +534,8 @@ static int i915_resume(struct drm_device *dev)
 
 	i915_restore_vga(dev);
 
+	intel_opregion_init(dev);
+
 	return 0;
 }
 
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 8daf0d84cd5a874861267cb3fd8b6f2605bbc750..e4bd01c511a94b7632627d6a5d2e00d034afc462 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -82,6 +82,14 @@ typedef struct _drm_i915_vbl_swap {
 	unsigned int sequence;
 } drm_i915_vbl_swap_t;
 
+struct intel_opregion {
+	struct opregion_header *header;
+	struct opregion_acpi *acpi;
+	struct opregion_swsci *swsci;
+	struct opregion_asle *asle;
+	int enabled;
+};
+
 typedef struct drm_i915_private {
 	drm_local_map_t *sarea;
 	drm_local_map_t *mmio_map;
@@ -122,6 +130,8 @@ typedef struct drm_i915_private {
 	drm_i915_vbl_swap_t vbl_swaps;
 	unsigned int swaps_pending;
 
+	struct intel_opregion opregion;
+
 	/* Register state */
 	u8 saveLBB;
 	u32 saveDSPACNTR;
@@ -244,6 +254,7 @@ extern int i915_vblank_pipe_get(struct drm_device *dev, void *data,
 				struct drm_file *file_priv);
 extern int i915_vblank_swap(struct drm_device *dev, void *data,
 			    struct drm_file *file_priv);
+extern void i915_enable_irq(drm_i915_private_t *dev_priv, u32 mask);
 
 /* i915_mem.c */
 extern int i915_mem_alloc(struct drm_device *dev, void *data,
@@ -258,6 +269,12 @@ extern void i915_mem_takedown(struct mem_block **heap);
 extern void i915_mem_release(struct drm_device * dev,
 			     struct drm_file *file_priv, struct mem_block *heap);
 
+/* i915_opregion.c */
+extern int intel_opregion_init(struct drm_device *dev);
+extern void intel_opregion_free(struct drm_device *dev);
+extern void opregion_asle_intr(struct drm_device *dev);
+extern void opregion_enable_asle(struct drm_device *dev);
+
 #define I915_READ(reg)          DRM_READ32(dev_priv->mmio_map, (reg))
 #define I915_WRITE(reg,val)     DRM_WRITE32(dev_priv->mmio_map, (reg), (val))
 #define I915_READ16(reg)	DRM_READ16(dev_priv->mmio_map, (reg))
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 24d11ed5bbc7a76d7cd914830c111872dabb0147..ae7d3a82a6d1279e726d603a3e739ce4e1e504b5 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -36,9 +36,11 @@
 /** These are the interrupts used by the driver */
 #define I915_INTERRUPT_ENABLE_MASK (I915_USER_INTERRUPT |		\
 				    I915_DISPLAY_PIPE_A_VBLANK_INTERRUPT | \
-				    I915_DISPLAY_PIPE_B_VBLANK_INTERRUPT)
+				    I915_DISPLAY_PIPE_B_VBLANK_INTERRUPT | \
+				    I915_ASLE_INTERRUPT |		\
+				    I915_DISPLAY_PIPE_B_EVENT_INTERRUPT)
 
-static inline void
+void
 i915_enable_irq(drm_i915_private_t *dev_priv, u32 mask)
 {
 	if ((dev_priv->irq_mask_reg & mask) != 0) {
@@ -274,6 +276,9 @@ irqreturn_t i915_driver_irq_handler(DRM_IRQ_ARGS)
 		return IRQ_NONE;
 	}
 
+	I915_WRITE(PIPEASTAT, pipea_stats);
+	I915_WRITE(PIPEBSTAT, pipeb_stats);
+
 	I915_WRITE(IIR, iir);
 	if (dev->pdev->msi_enabled)
 		I915_WRITE(IMR, dev_priv->irq_mask_reg);
@@ -306,14 +311,14 @@ irqreturn_t i915_driver_irq_handler(DRM_IRQ_ARGS)
 
 		if (dev_priv->swaps_pending > 0)
 			drm_locked_tasklet(dev, i915_vblank_tasklet);
-		I915_WRITE(PIPEASTAT,
-			pipea_stats|I915_VBLANK_INTERRUPT_ENABLE|
-			PIPE_VBLANK_INTERRUPT_STATUS);
-		I915_WRITE(PIPEBSTAT,
-			pipeb_stats|I915_VBLANK_INTERRUPT_ENABLE|
-			PIPE_VBLANK_INTERRUPT_STATUS);
 	}
 
+	if (iir & I915_ASLE_INTERRUPT)
+		opregion_asle_intr(dev);
+
+	if (iir & I915_DISPLAY_PIPE_B_EVENT_INTERRUPT)
+		opregion_asle_intr(dev);
+
 	return IRQ_HANDLED;
 }
 
@@ -661,10 +666,14 @@ void i915_driver_irq_postinstall(struct drm_device * dev)
 	if (dev_priv->vblank_pipe & DRM_I915_VBLANK_PIPE_B)
 		dev_priv->irq_mask_reg &= ~I915_DISPLAY_PIPE_B_VBLANK_INTERRUPT;
 
+	dev_priv->irq_mask_reg &= I915_INTERRUPT_ENABLE_MASK;
+
 	I915_WRITE(IMR, dev_priv->irq_mask_reg);
 	I915_WRITE(IER, I915_INTERRUPT_ENABLE_MASK);
 	(void) I915_READ(IER);
 
+	opregion_enable_asle(dev);
+
 	DRM_INIT_WAITQUEUE(&dev_priv->irq_queue);
 }
 
diff --git a/drivers/gpu/drm/i915/i915_opregion.c b/drivers/gpu/drm/i915/i915_opregion.c
new file mode 100644
index 0000000000000000000000000000000000000000..1787a0c7e3abf09acc363b87495190ce362db6ce
--- /dev/null
+++ b/drivers/gpu/drm/i915/i915_opregion.c
@@ -0,0 +1,371 @@
+/*
+ * Copyright 2008 Intel Corporation <hong.liu@intel.com>
+ * Copyright 2008 Red Hat <mjg@redhat.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sub license, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NON-INFRINGEMENT.  IN NO EVENT SHALL INTEL AND/OR ITS SUPPLIERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+
+#include <linux/acpi.h>
+
+#include "drmP.h"
+#include "i915_drm.h"
+#include "i915_drv.h"
+
+#define PCI_ASLE 0xe4
+#define PCI_LBPC 0xf4
+#define PCI_ASLS 0xfc
+
+#define OPREGION_SZ            (8*1024)
+#define OPREGION_HEADER_OFFSET 0
+#define OPREGION_ACPI_OFFSET   0x100
+#define OPREGION_SWSCI_OFFSET  0x200
+#define OPREGION_ASLE_OFFSET   0x300
+#define OPREGION_VBT_OFFSET    0x1000
+
+#define OPREGION_SIGNATURE "IntelGraphicsMem"
+#define MBOX_ACPI      (1<<0)
+#define MBOX_SWSCI     (1<<1)
+#define MBOX_ASLE      (1<<2)
+
+struct opregion_header {
+       u8 signature[16];
+       u32 size;
+       u32 opregion_ver;
+       u8 bios_ver[32];
+       u8 vbios_ver[16];
+       u8 driver_ver[16];
+       u32 mboxes;
+       u8 reserved[164];
+} __attribute__((packed));
+
+/* OpRegion mailbox #1: public ACPI methods */
+struct opregion_acpi {
+       u32 drdy;       /* driver readiness */
+       u32 csts;       /* notification status */
+       u32 cevt;       /* current event */
+       u8 rsvd1[20];
+       u32 didl[8];    /* supported display devices ID list */
+       u32 cpdl[8];    /* currently presented display list */
+       u32 cadl[8];    /* currently active display list */
+       u32 nadl[8];    /* next active devices list */
+       u32 aslp;       /* ASL sleep time-out */
+       u32 tidx;       /* toggle table index */
+       u32 chpd;       /* current hotplug enable indicator */
+       u32 clid;       /* current lid state*/
+       u32 cdck;       /* current docking state */
+       u32 sxsw;       /* Sx state resume */
+       u32 evts;       /* ASL supported events */
+       u32 cnot;       /* current OS notification */
+       u32 nrdy;       /* driver status */
+       u8 rsvd2[60];
+} __attribute__((packed));
+
+/* OpRegion mailbox #2: SWSCI */
+struct opregion_swsci {
+       u32 scic;       /* SWSCI command|status|data */
+       u32 parm;       /* command parameters */
+       u32 dslp;       /* driver sleep time-out */
+       u8 rsvd[244];
+} __attribute__((packed));
+
+/* OpRegion mailbox #3: ASLE */
+struct opregion_asle {
+       u32 ardy;       /* driver readiness */
+       u32 aslc;       /* ASLE interrupt command */
+       u32 tche;       /* technology enabled indicator */
+       u32 alsi;       /* current ALS illuminance reading */
+       u32 bclp;       /* backlight brightness to set */
+       u32 pfit;       /* panel fitting state */
+       u32 cblv;       /* current brightness level */
+       u16 bclm[20];   /* backlight level duty cycle mapping table */
+       u32 cpfm;       /* current panel fitting mode */
+       u32 epfm;       /* enabled panel fitting modes */
+       u8 plut[74];    /* panel LUT and identifier */
+       u32 pfmb;       /* PWM freq and min brightness */
+       u8 rsvd[102];
+} __attribute__((packed));
+
+/* ASLE irq request bits */
+#define ASLE_SET_ALS_ILLUM     (1 << 0)
+#define ASLE_SET_BACKLIGHT     (1 << 1)
+#define ASLE_SET_PFIT          (1 << 2)
+#define ASLE_SET_PWM_FREQ      (1 << 3)
+#define ASLE_REQ_MSK           0xf
+
+/* response bits of ASLE irq request */
+#define ASLE_ALS_ILLUM_FAIL    (2<<10)
+#define ASLE_BACKLIGHT_FAIL    (2<<12)
+#define ASLE_PFIT_FAIL         (2<<14)
+#define ASLE_PWM_FREQ_FAIL     (2<<16)
+
+/* ASLE backlight brightness to set */
+#define ASLE_BCLP_VALID                (1<<31)
+#define ASLE_BCLP_MSK          (~(1<<31))
+
+/* ASLE panel fitting request */
+#define ASLE_PFIT_VALID         (1<<31)
+#define ASLE_PFIT_CENTER (1<<0)
+#define ASLE_PFIT_STRETCH_TEXT (1<<1)
+#define ASLE_PFIT_STRETCH_GFX (1<<2)
+
+/* PWM frequency and minimum brightness */
+#define ASLE_PFMB_BRIGHTNESS_MASK (0xff)
+#define ASLE_PFMB_BRIGHTNESS_VALID (1<<8)
+#define ASLE_PFMB_PWM_MASK (0x7ffffe00)
+#define ASLE_PFMB_PWM_VALID (1<<31)
+
+#define ASLE_CBLV_VALID         (1<<31)
+
+static u32 asle_set_backlight(struct drm_device *dev, u32 bclp)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct opregion_asle *asle = dev_priv->opregion.asle;
+	u32 blc_pwm_ctl, blc_pwm_ctl2;
+
+	if (!(bclp & ASLE_BCLP_VALID))
+		return ASLE_BACKLIGHT_FAIL;
+
+	bclp &= ASLE_BCLP_MSK;
+	if (bclp < 0 || bclp > 255)
+		return ASLE_BACKLIGHT_FAIL;
+
+	blc_pwm_ctl = I915_READ(BLC_PWM_CTL);
+	blc_pwm_ctl &= ~BACKLIGHT_DUTY_CYCLE_MASK;
+	blc_pwm_ctl2 = I915_READ(BLC_PWM_CTL2);
+
+	if (blc_pwm_ctl2 & BLM_COMBINATION_MODE)
+		pci_write_config_dword(dev->pdev, PCI_LBPC, bclp);
+	else
+		I915_WRITE(BLC_PWM_CTL, blc_pwm_ctl | ((bclp * 0x101)-1));
+
+	asle->cblv = (bclp*0x64)/0xff | ASLE_CBLV_VALID;
+
+	return 0;
+}
+
+static u32 asle_set_als_illum(struct drm_device *dev, u32 alsi)
+{
+	/* alsi is the current ALS reading in lux. 0 indicates below sensor
+	   range, 0xffff indicates above sensor range. 1-0xfffe are valid */
+	return 0;
+}
+
+static u32 asle_set_pwm_freq(struct drm_device *dev, u32 pfmb)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	if (pfmb & ASLE_PFMB_PWM_VALID) {
+		u32 blc_pwm_ctl = I915_READ(BLC_PWM_CTL);
+		u32 pwm = pfmb & ASLE_PFMB_PWM_MASK;
+		blc_pwm_ctl &= BACKLIGHT_DUTY_CYCLE_MASK;
+		pwm = pwm >> 9;
+		/* FIXME - what do we do with the PWM? */
+	}
+	return 0;
+}
+
+static u32 asle_set_pfit(struct drm_device *dev, u32 pfit)
+{
+	/* Panel fitting is currently controlled by the X code, so this is a
+	   noop until modesetting support works fully */
+	if (!(pfit & ASLE_PFIT_VALID))
+		return ASLE_PFIT_FAIL;
+	return 0;
+}
+
+void opregion_asle_intr(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct opregion_asle *asle = dev_priv->opregion.asle;
+	u32 asle_stat = 0;
+	u32 asle_req;
+
+	if (!asle)
+		return;
+
+	asle_req = asle->aslc & ASLE_REQ_MSK;
+
+	if (!asle_req) {
+		DRM_DEBUG("non asle set request??\n");
+		return;
+	}
+
+	if (asle_req & ASLE_SET_ALS_ILLUM)
+		asle_stat |= asle_set_als_illum(dev, asle->alsi);
+
+	if (asle_req & ASLE_SET_BACKLIGHT)
+		asle_stat |= asle_set_backlight(dev, asle->bclp);
+
+	if (asle_req & ASLE_SET_PFIT)
+		asle_stat |= asle_set_pfit(dev, asle->pfit);
+
+	if (asle_req & ASLE_SET_PWM_FREQ)
+		asle_stat |= asle_set_pwm_freq(dev, asle->pfmb);
+
+	asle->aslc = asle_stat;
+}
+
+#define ASLE_ALS_EN    (1<<0)
+#define ASLE_BLC_EN    (1<<1)
+#define ASLE_PFIT_EN   (1<<2)
+#define ASLE_PFMB_EN   (1<<3)
+
+void opregion_enable_asle(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct opregion_asle *asle = dev_priv->opregion.asle;
+
+	if (asle) {
+		u32 pipeb_stats = I915_READ(PIPEBSTAT);
+		if (IS_MOBILE(dev)) {
+			/* Many devices trigger events with a write to the
+			   legacy backlight controller, so we need to ensure
+			   that it's able to generate interrupts */
+			I915_WRITE(PIPEBSTAT, pipeb_stats |=
+				   I915_LEGACY_BLC_EVENT_ENABLE);
+			i915_enable_irq(dev_priv, I915_ASLE_INTERRUPT |
+					I915_DISPLAY_PIPE_B_EVENT_INTERRUPT);
+		} else
+			i915_enable_irq(dev_priv, I915_ASLE_INTERRUPT);
+
+		asle->tche = ASLE_ALS_EN | ASLE_BLC_EN | ASLE_PFIT_EN |
+			ASLE_PFMB_EN;
+		asle->ardy = 1;
+	}
+}
+
+#define ACPI_EV_DISPLAY_SWITCH (1<<0)
+#define ACPI_EV_LID            (1<<1)
+#define ACPI_EV_DOCK           (1<<2)
+
+static struct intel_opregion *system_opregion;
+
+int intel_opregion_video_event(struct notifier_block *nb, unsigned long val,
+			       void *data)
+{
+	/* The only video events relevant to opregion are 0x80. These indicate
+	   either a docking event, lid switch or display switch request. In
+	   Linux, these are handled by the dock, button and video drivers.
+	   We might want to fix the video driver to be opregion-aware in
+	   future, but right now we just indicate to the firmware that the
+	   request has been handled */
+
+	struct opregion_acpi *acpi;
+
+	if (!system_opregion)
+		return NOTIFY_DONE;
+
+	acpi = system_opregion->acpi;
+	acpi->csts = 0;
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block intel_opregion_notifier = {
+	.notifier_call = intel_opregion_video_event,
+};
+
+int intel_opregion_init(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct intel_opregion *opregion = &dev_priv->opregion;
+	void *base;
+	u32 asls, mboxes;
+	int err = 0;
+
+	pci_read_config_dword(dev->pdev, PCI_ASLS, &asls);
+	DRM_DEBUG("graphic opregion physical addr: 0x%x\n", asls);
+	if (asls == 0) {
+		DRM_DEBUG("ACPI OpRegion not supported!\n");
+		return -ENOTSUPP;
+	}
+
+	base = ioremap(asls, OPREGION_SZ);
+	if (!base)
+		return -ENOMEM;
+
+	opregion->header = base;
+	if (memcmp(opregion->header->signature, OPREGION_SIGNATURE, 16)) {
+		DRM_DEBUG("opregion signature mismatch\n");
+		err = -EINVAL;
+		goto err_out;
+	}
+
+	mboxes = opregion->header->mboxes;
+	if (mboxes & MBOX_ACPI) {
+		DRM_DEBUG("Public ACPI methods supported\n");
+		opregion->acpi = base + OPREGION_ACPI_OFFSET;
+	} else {
+		DRM_DEBUG("Public ACPI methods not supported\n");
+		err = -ENOTSUPP;
+		goto err_out;
+	}
+	opregion->enabled = 1;
+
+	if (mboxes & MBOX_SWSCI) {
+		DRM_DEBUG("SWSCI supported\n");
+		opregion->swsci = base + OPREGION_SWSCI_OFFSET;
+	}
+	if (mboxes & MBOX_ASLE) {
+		DRM_DEBUG("ASLE supported\n");
+		opregion->asle = base + OPREGION_ASLE_OFFSET;
+	}
+
+	/* Notify BIOS we are ready to handle ACPI video ext notifs.
+	 * Right now, all the events are handled by the ACPI video module.
+	 * We don't actually need to do anything with them. */
+	opregion->acpi->csts = 0;
+	opregion->acpi->drdy = 1;
+
+	system_opregion = opregion;
+	register_acpi_notifier(&intel_opregion_notifier);
+
+	return 0;
+
+err_out:
+	iounmap(opregion->header);
+	opregion->header = NULL;
+	return err;
+}
+
+void intel_opregion_free(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct intel_opregion *opregion = &dev_priv->opregion;
+
+	if (!opregion->enabled)
+		return;
+
+	opregion->acpi->drdy = 0;
+
+	system_opregion = NULL;
+	unregister_acpi_notifier(&intel_opregion_notifier);
+
+	/* just clear all opregion memory pointers now */
+	iounmap(opregion->header);
+	opregion->header = NULL;
+	opregion->acpi = NULL;
+	opregion->swsci = NULL;
+	opregion->asle = NULL;
+
+	opregion->enabled = 0;
+}
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 477c64e6ba2da804a18a61678d833fe2941f29ab..43ad2cb8b9f5d1027d74b83f21dce828f98262a1 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -740,6 +740,7 @@
 #define BLC_PWM_CTL		0x61254
 #define   BACKLIGHT_MODULATION_FREQ_SHIFT		(17)
 #define BLC_PWM_CTL2		0x61250 /* 965+ only */
+#define   BLM_COMBINATION_MODE (1 << 30)
 /*
  * This is the most significant 15 bits of the number of backlight cycles in a
  * complete cycle of the modulated backlight control.