drivers/platform/x86/apple-gmux.c - kernel/msm-4.9 - Gitiles

 /*
  *  Gmux driver for Apple laptops
  *
  *  Copyright (C) Canonical Ltd. <seth.forshee@canonical.com>
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License version 2 as
  *  published by the Free Software Foundation.
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/backlight.h>
 #include <linux/acpi.h>
 #include <linux/pnp.h>
 #include <linux/apple_bl.h>
 #include <linux/slab.h>
 #include <linux/delay.h>
 #include <acpi/video.h>
 #include <asm/io.h>

 struct apple_gmux_data {
 	unsigned long iostart;
 	unsigned long iolen;
 	bool indexed;
 	struct mutex index_lock;

 	struct backlight_device *bdev;
 };

 /*
  * gmux port offsets. Many of these are not yet used, but may be in the
  * future, and it's useful to have them documented here anyhow.
  */
 #define GMUX_PORT_VERSION_MAJOR		0x04
 #define GMUX_PORT_VERSION_MINOR		0x05
 #define GMUX_PORT_VERSION_RELEASE	0x06
 #define GMUX_PORT_SWITCH_DISPLAY	0x10
 #define GMUX_PORT_SWITCH_GET_DISPLAY	0x11
 #define GMUX_PORT_INTERRUPT_ENABLE	0x14
 #define GMUX_PORT_INTERRUPT_STATUS	0x16
 #define GMUX_PORT_SWITCH_DDC		0x28
 #define GMUX_PORT_SWITCH_EXTERNAL	0x40
 #define GMUX_PORT_SWITCH_GET_EXTERNAL	0x41
 #define GMUX_PORT_DISCRETE_POWER	0x50
 #define GMUX_PORT_MAX_BRIGHTNESS	0x70
 #define GMUX_PORT_BRIGHTNESS		0x74
 #define GMUX_PORT_VALUE			0xc2
 #define GMUX_PORT_READ			0xd0
 #define GMUX_PORT_WRITE			0xd4

 #define GMUX_MIN_IO_LEN			(GMUX_PORT_BRIGHTNESS + 4)

 #define GMUX_INTERRUPT_ENABLE		0xff
 #define GMUX_INTERRUPT_DISABLE		0x00

 #define GMUX_INTERRUPT_STATUS_ACTIVE	0
 #define GMUX_INTERRUPT_STATUS_DISPLAY	(1 << 0)
 #define GMUX_INTERRUPT_STATUS_POWER	(1 << 2)
 #define GMUX_INTERRUPT_STATUS_HOTPLUG	(1 << 3)

 #define GMUX_BRIGHTNESS_MASK		0x00ffffff
 #define GMUX_MAX_BRIGHTNESS		GMUX_BRIGHTNESS_MASK

 static u8 gmux_pio_read8(struct apple_gmux_data *gmux_data, int port)
 {
 	return inb(gmux_data->iostart + port);
 }

 static void gmux_pio_write8(struct apple_gmux_data *gmux_data, int port,
 			       u8 val)
 {
 	outb(val, gmux_data->iostart + port);
 }

 static u32 gmux_pio_read32(struct apple_gmux_data *gmux_data, int port)
 {
 	return inl(gmux_data->iostart + port);
 }

 static void gmux_pio_write32(struct apple_gmux_data *gmux_data, int port,
 			     u32 val)
 {
 	int i;
 	u8 tmpval;

 	for (i = 0; i < 4; i++) {
 		tmpval = (val >> (i * 8)) & 0xff;
 		outb(tmpval, port + i);
 	}
 }

 static int gmux_index_wait_ready(struct apple_gmux_data *gmux_data)
 {
 	int i = 200;
 	u8 gwr = inb(gmux_data->iostart + GMUX_PORT_WRITE);

 	while (i && (gwr & 0x01)) {
 		inb(gmux_data->iostart + GMUX_PORT_READ);
 		gwr = inb(gmux_data->iostart + GMUX_PORT_WRITE);
 		udelay(100);
 		i--;
 	}

 	return !!i;
 }

 static int gmux_index_wait_complete(struct apple_gmux_data *gmux_data)
 {
 	int i = 200;
 	u8 gwr = inb(gmux_data->iostart + GMUX_PORT_WRITE);

 	while (i && !(gwr & 0x01)) {
 		gwr = inb(gmux_data->iostart + GMUX_PORT_WRITE);
 		udelay(100);
 		i--;
 	}

 	if (gwr & 0x01)
 		inb(gmux_data->iostart + GMUX_PORT_READ);

 	return !!i;
 }

 static u8 gmux_index_read8(struct apple_gmux_data *gmux_data, int port)
 {
 	u8 val;

 	mutex_lock(&gmux_data->index_lock);
 	outb((port & 0xff), gmux_data->iostart + GMUX_PORT_READ);
 	gmux_index_wait_ready(gmux_data);
 	val = inb(gmux_data->iostart + GMUX_PORT_VALUE);
 	mutex_unlock(&gmux_data->index_lock);

 	return val;
 }

 static void gmux_index_write8(struct apple_gmux_data *gmux_data, int port,
 			      u8 val)
 {
 	mutex_lock(&gmux_data->index_lock);
 	outb(val, gmux_data->iostart + GMUX_PORT_VALUE);
 	gmux_index_wait_ready(gmux_data);
 	outb(port & 0xff, gmux_data->iostart + GMUX_PORT_WRITE);
 	gmux_index_wait_complete(gmux_data);
 	mutex_unlock(&gmux_data->index_lock);
 }

 static u32 gmux_index_read32(struct apple_gmux_data *gmux_data, int port)
 {
 	u32 val;

 	mutex_lock(&gmux_data->index_lock);
 	outb((port & 0xff), gmux_data->iostart + GMUX_PORT_READ);
 	gmux_index_wait_ready(gmux_data);
 	val = inl(gmux_data->iostart + GMUX_PORT_VALUE);
 	mutex_unlock(&gmux_data->index_lock);

 	return val;
 }

 static void gmux_index_write32(struct apple_gmux_data *gmux_data, int port,
 			       u32 val)
 {
 	int i;
 	u8 tmpval;

 	mutex_lock(&gmux_data->index_lock);

 	for (i = 0; i < 4; i++) {
 		tmpval = (val >> (i * 8)) & 0xff;
 		outb(tmpval, gmux_data->iostart + GMUX_PORT_VALUE + i);
 	}

 	gmux_index_wait_ready(gmux_data);
 	outb(port & 0xff, gmux_data->iostart + GMUX_PORT_WRITE);
 	gmux_index_wait_complete(gmux_data);
 	mutex_unlock(&gmux_data->index_lock);
 }

 static u8 gmux_read8(struct apple_gmux_data *gmux_data, int port)
 {
 	if (gmux_data->indexed)
 		return gmux_index_read8(gmux_data, port);
 	else
 		return gmux_pio_read8(gmux_data, port);
 }

 static void gmux_write8(struct apple_gmux_data *gmux_data, int port, u8 val)
 {
 	if (gmux_data->indexed)
 		gmux_index_write8(gmux_data, port, val);
 	else
 		gmux_pio_write8(gmux_data, port, val);
 }

 static u32 gmux_read32(struct apple_gmux_data *gmux_data, int port)
 {
 	if (gmux_data->indexed)
 		return gmux_index_read32(gmux_data, port);
 	else
 		return gmux_pio_read32(gmux_data, port);
 }

 static void gmux_write32(struct apple_gmux_data *gmux_data, int port,
 			     u32 val)
 {
 	if (gmux_data->indexed)
 		gmux_index_write32(gmux_data, port, val);
 	else
 		gmux_pio_write32(gmux_data, port, val);
 }

 static bool gmux_is_indexed(struct apple_gmux_data *gmux_data)
 {
 	u16 val;

 	outb(0xaa, gmux_data->iostart + 0xcc);
 	outb(0x55, gmux_data->iostart + 0xcd);
 	outb(0x00, gmux_data->iostart + 0xce);

 	val = inb(gmux_data->iostart + 0xcc) |
 		(inb(gmux_data->iostart + 0xcd) << 8);

 	if (val == 0x55aa)
 		return true;

 	return false;
 }

 static int gmux_get_brightness(struct backlight_device *bd)
 {
 	struct apple_gmux_data *gmux_data = bl_get_data(bd);
 	return gmux_read32(gmux_data, GMUX_PORT_BRIGHTNESS) &
 	       GMUX_BRIGHTNESS_MASK;
 }

 static int gmux_update_status(struct backlight_device *bd)
 {
 	struct apple_gmux_data *gmux_data = bl_get_data(bd);
 	u32 brightness = bd->props.brightness;

 	if (bd->props.state & BL_CORE_SUSPENDED)
 		return 0;

 	gmux_write32(gmux_data, GMUX_PORT_BRIGHTNESS, brightness);

 	return 0;
 }

 static const struct backlight_ops gmux_bl_ops = {
 	.options = BL_CORE_SUSPENDRESUME,
 	.get_brightness = gmux_get_brightness,
 	.update_status = gmux_update_status,
 };

 static int __devinit gmux_probe(struct pnp_dev *pnp,
 				const struct pnp_device_id *id)
 {
 	struct apple_gmux_data *gmux_data;
 	struct resource *res;
 	struct backlight_properties props;
 	struct backlight_device *bdev;
 	u8 ver_major, ver_minor, ver_release;
 	int ret = -ENXIO;

 	gmux_data = kzalloc(sizeof(*gmux_data), GFP_KERNEL);
 	if (!gmux_data)
 		return -ENOMEM;
 	pnp_set_drvdata(pnp, gmux_data);

 	res = pnp_get_resource(pnp, IORESOURCE_IO, 0);
 	if (!res) {
 		pr_err("Failed to find gmux I/O resource\n");
 		goto err_free;
 	}

 	gmux_data->iostart = res->start;
 	gmux_data->iolen = res->end - res->start;

 	if (gmux_data->iolen < GMUX_MIN_IO_LEN) {
 		pr_err("gmux I/O region too small (%lu < %u)\n",
 		       gmux_data->iolen, GMUX_MIN_IO_LEN);
 		goto err_free;
 	}

 	if (!request_region(gmux_data->iostart, gmux_data->iolen,
 			    "Apple gmux")) {
 		pr_err("gmux I/O already in use\n");
 		goto err_free;
 	}

 	/*
 	 * Invalid version information may indicate either that the gmux
 	 * device isn't present or that it's a new one that uses indexed
 	 * io
 	 */

 	ver_major = gmux_read8(gmux_data, GMUX_PORT_VERSION_MAJOR);
 	ver_minor = gmux_read8(gmux_data, GMUX_PORT_VERSION_MINOR);
 	ver_release = gmux_read8(gmux_data, GMUX_PORT_VERSION_RELEASE);
 	if (ver_major == 0xff && ver_minor == 0xff && ver_release == 0xff) {
 		if (gmux_is_indexed(gmux_data)) {
 			mutex_init(&gmux_data->index_lock);
 			gmux_data->indexed = true;
 		} else {
 			pr_info("gmux device not present\n");
 			ret = -ENODEV;
 			goto err_release;
 		}
 		pr_info("Found indexed gmux\n");
 	} else {
 		pr_info("Found gmux version %d.%d.%d\n", ver_major, ver_minor,
 			ver_release);
 	}

 	memset(&props, 0, sizeof(props));
 	props.type = BACKLIGHT_PLATFORM;
 	props.max_brightness = gmux_read32(gmux_data, GMUX_PORT_MAX_BRIGHTNESS);

 	/*
 	 * Currently it's assumed that the maximum brightness is less than
 	 * 2^24 for compatibility with old gmux versions. Cap the max
 	 * brightness at this value, but print a warning if the hardware
 	 * reports something higher so that it can be fixed.
 	 */
 	if (WARN_ON(props.max_brightness > GMUX_MAX_BRIGHTNESS))
 		props.max_brightness = GMUX_MAX_BRIGHTNESS;

 	bdev = backlight_device_register("gmux_backlight", &pnp->dev,
 					 gmux_data, &gmux_bl_ops, &props);
 	if (IS_ERR(bdev)) {
 		ret = PTR_ERR(bdev);
 		goto err_release;
 	}

 	gmux_data->bdev = bdev;
 	bdev->props.brightness = gmux_get_brightness(bdev);
 	backlight_update_status(bdev);

 	/*
 	 * The backlight situation on Macs is complicated. If the gmux is
 	 * present it's the best choice, because it always works for
 	 * backlight control and supports more levels than other options.
 	 * Disable the other backlight choices.
 	 */
 	acpi_video_dmi_promote_vendor();
 #if defined (CONFIG_ACPI_VIDEO) || defined (CONFIG_ACPI_VIDEO_MODULE)
 	acpi_video_unregister();
 #endif
 	apple_bl_unregister();

 	return 0;

 err_release:
 	release_region(gmux_data->iostart, gmux_data->iolen);
 err_free:
 	kfree(gmux_data);
 	return ret;
 }

 static void __devexit gmux_remove(struct pnp_dev *pnp)
 {
 	struct apple_gmux_data *gmux_data = pnp_get_drvdata(pnp);

 	backlight_device_unregister(gmux_data->bdev);
 	release_region(gmux_data->iostart, gmux_data->iolen);
 	kfree(gmux_data);

 	acpi_video_dmi_demote_vendor();
 #if defined (CONFIG_ACPI_VIDEO) || defined (CONFIG_ACPI_VIDEO_MODULE)
 	acpi_video_register();
 #endif
 	apple_bl_register();
 }

 static const struct pnp_device_id gmux_device_ids[] = {
 	{"APP000B", 0},
 	{"", 0}
 };

 static struct pnp_driver gmux_pnp_driver = {
 	.name		= "apple-gmux",
 	.probe		= gmux_probe,
 	.remove		= __devexit_p(gmux_remove),
 	.id_table	= gmux_device_ids,
 };

 static int __init apple_gmux_init(void)
 {
 	return pnp_register_driver(&gmux_pnp_driver);
 }

 static void __exit apple_gmux_exit(void)
 {
 	pnp_unregister_driver(&gmux_pnp_driver);
 }

 module_init(apple_gmux_init);
 module_exit(apple_gmux_exit);

 MODULE_AUTHOR("Seth Forshee <seth.forshee@canonical.com>");
 MODULE_DESCRIPTION("Apple Gmux Driver");
 MODULE_LICENSE("GPL");
 MODULE_DEVICE_TABLE(pnp, gmux_device_ids);
	/*
	* Gmux driver for Apple laptops
	*
	* Copyright (C) Canonical Ltd. <seth.forshee@canonical.com>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/module.h>
	#include <linux/kernel.h>
	#include <linux/init.h>
	#include <linux/backlight.h>
	#include <linux/acpi.h>
	#include <linux/pnp.h>
	#include <linux/apple_bl.h>
	#include <linux/slab.h>
	#include <linux/delay.h>
	#include <acpi/video.h>
	#include <asm/io.h>

	struct apple_gmux_data {
	unsigned long iostart;
	unsigned long iolen;
	bool indexed;
	struct mutex index_lock;

	struct backlight_device *bdev;
	};

	/*
	* gmux port offsets. Many of these are not yet used, but may be in the
	* future, and it's useful to have them documented here anyhow.
	*/
	#define GMUX_PORT_VERSION_MAJOR 0x04
	#define GMUX_PORT_VERSION_MINOR 0x05
	#define GMUX_PORT_VERSION_RELEASE 0x06
	#define GMUX_PORT_SWITCH_DISPLAY 0x10
	#define GMUX_PORT_SWITCH_GET_DISPLAY 0x11
	#define GMUX_PORT_INTERRUPT_ENABLE 0x14
	#define GMUX_PORT_INTERRUPT_STATUS 0x16
	#define GMUX_PORT_SWITCH_DDC 0x28
	#define GMUX_PORT_SWITCH_EXTERNAL 0x40
	#define GMUX_PORT_SWITCH_GET_EXTERNAL 0x41
	#define GMUX_PORT_DISCRETE_POWER 0x50
	#define GMUX_PORT_MAX_BRIGHTNESS 0x70
	#define GMUX_PORT_BRIGHTNESS 0x74
	#define GMUX_PORT_VALUE 0xc2
	#define GMUX_PORT_READ 0xd0
	#define GMUX_PORT_WRITE 0xd4

	#define GMUX_MIN_IO_LEN (GMUX_PORT_BRIGHTNESS + 4)

	#define GMUX_INTERRUPT_ENABLE 0xff
	#define GMUX_INTERRUPT_DISABLE 0x00

	#define GMUX_INTERRUPT_STATUS_ACTIVE 0
	#define GMUX_INTERRUPT_STATUS_DISPLAY (1 << 0)
	#define GMUX_INTERRUPT_STATUS_POWER (1 << 2)
	#define GMUX_INTERRUPT_STATUS_HOTPLUG (1 << 3)

	#define GMUX_BRIGHTNESS_MASK 0x00ffffff
	#define GMUX_MAX_BRIGHTNESS GMUX_BRIGHTNESS_MASK

	static u8 gmux_pio_read8(struct apple_gmux_data *gmux_data, int port)
	{
	return inb(gmux_data->iostart + port);
	}

	static void gmux_pio_write8(struct apple_gmux_data *gmux_data, int port,
	u8 val)
	{
	outb(val, gmux_data->iostart + port);
	}

	static u32 gmux_pio_read32(struct apple_gmux_data *gmux_data, int port)
	{
	return inl(gmux_data->iostart + port);
	}

	static void gmux_pio_write32(struct apple_gmux_data *gmux_data, int port,
	u32 val)
	{
	int i;
	u8 tmpval;

	for (i = 0; i < 4; i++) {
	tmpval = (val >> (i * 8)) & 0xff;
	outb(tmpval, port + i);
	}
	}

	static int gmux_index_wait_ready(struct apple_gmux_data *gmux_data)
	{
	int i = 200;
	u8 gwr = inb(gmux_data->iostart + GMUX_PORT_WRITE);

	while (i && (gwr & 0x01)) {
	inb(gmux_data->iostart + GMUX_PORT_READ);
	gwr = inb(gmux_data->iostart + GMUX_PORT_WRITE);
	udelay(100);
	i--;
	}

	return !!i;
	}

	static int gmux_index_wait_complete(struct apple_gmux_data *gmux_data)
	{
	int i = 200;
	u8 gwr = inb(gmux_data->iostart + GMUX_PORT_WRITE);

	while (i && !(gwr & 0x01)) {
	gwr = inb(gmux_data->iostart + GMUX_PORT_WRITE);
	udelay(100);
	i--;
	}

	if (gwr & 0x01)
	inb(gmux_data->iostart + GMUX_PORT_READ);

	return !!i;
	}

	static u8 gmux_index_read8(struct apple_gmux_data *gmux_data, int port)
	{
	u8 val;

	mutex_lock(&gmux_data->index_lock);
	outb((port & 0xff), gmux_data->iostart + GMUX_PORT_READ);
	gmux_index_wait_ready(gmux_data);
	val = inb(gmux_data->iostart + GMUX_PORT_VALUE);
	mutex_unlock(&gmux_data->index_lock);

	return val;
	}

	static void gmux_index_write8(struct apple_gmux_data *gmux_data, int port,
	u8 val)
	{
	mutex_lock(&gmux_data->index_lock);
	outb(val, gmux_data->iostart + GMUX_PORT_VALUE);
	gmux_index_wait_ready(gmux_data);
	outb(port & 0xff, gmux_data->iostart + GMUX_PORT_WRITE);
	gmux_index_wait_complete(gmux_data);
	mutex_unlock(&gmux_data->index_lock);
	}

	static u32 gmux_index_read32(struct apple_gmux_data *gmux_data, int port)
	{
	u32 val;

	mutex_lock(&gmux_data->index_lock);
	outb((port & 0xff), gmux_data->iostart + GMUX_PORT_READ);
	gmux_index_wait_ready(gmux_data);
	val = inl(gmux_data->iostart + GMUX_PORT_VALUE);
	mutex_unlock(&gmux_data->index_lock);

	return val;
	}

	static void gmux_index_write32(struct apple_gmux_data *gmux_data, int port,
	u32 val)
	{
	int i;
	u8 tmpval;

	mutex_lock(&gmux_data->index_lock);

	for (i = 0; i < 4; i++) {
	tmpval = (val >> (i * 8)) & 0xff;
	outb(tmpval, gmux_data->iostart + GMUX_PORT_VALUE + i);
	}

	gmux_index_wait_ready(gmux_data);
	outb(port & 0xff, gmux_data->iostart + GMUX_PORT_WRITE);
	gmux_index_wait_complete(gmux_data);
	mutex_unlock(&gmux_data->index_lock);
	}

	static u8 gmux_read8(struct apple_gmux_data *gmux_data, int port)
	{
	if (gmux_data->indexed)
	return gmux_index_read8(gmux_data, port);
	else
	return gmux_pio_read8(gmux_data, port);
	}

	static void gmux_write8(struct apple_gmux_data *gmux_data, int port, u8 val)
	{
	if (gmux_data->indexed)
	gmux_index_write8(gmux_data, port, val);
	else
	gmux_pio_write8(gmux_data, port, val);
	}

	static u32 gmux_read32(struct apple_gmux_data *gmux_data, int port)
	{
	if (gmux_data->indexed)
	return gmux_index_read32(gmux_data, port);
	else
	return gmux_pio_read32(gmux_data, port);
	}

	static void gmux_write32(struct apple_gmux_data *gmux_data, int port,
	u32 val)
	{
	if (gmux_data->indexed)
	gmux_index_write32(gmux_data, port, val);
	else
	gmux_pio_write32(gmux_data, port, val);
	}

	static bool gmux_is_indexed(struct apple_gmux_data *gmux_data)
	{
	u16 val;

	outb(0xaa, gmux_data->iostart + 0xcc);
	outb(0x55, gmux_data->iostart + 0xcd);
	outb(0x00, gmux_data->iostart + 0xce);

	val = inb(gmux_data->iostart + 0xcc) \|
	(inb(gmux_data->iostart + 0xcd) << 8);

	if (val == 0x55aa)
	return true;

	return false;
	}

	static int gmux_get_brightness(struct backlight_device *bd)
	{
	struct apple_gmux_data *gmux_data = bl_get_data(bd);
	return gmux_read32(gmux_data, GMUX_PORT_BRIGHTNESS) &
	GMUX_BRIGHTNESS_MASK;
	}

	static int gmux_update_status(struct backlight_device *bd)
	{
	struct apple_gmux_data *gmux_data = bl_get_data(bd);
	u32 brightness = bd->props.brightness;

	if (bd->props.state & BL_CORE_SUSPENDED)
	return 0;

	gmux_write32(gmux_data, GMUX_PORT_BRIGHTNESS, brightness);

	return 0;
	}

	static const struct backlight_ops gmux_bl_ops = {
	.options = BL_CORE_SUSPENDRESUME,
	.get_brightness = gmux_get_brightness,
	.update_status = gmux_update_status,
	};

	static int __devinit gmux_probe(struct pnp_dev *pnp,
	const struct pnp_device_id *id)
	{
	struct apple_gmux_data *gmux_data;
	struct resource *res;
	struct backlight_properties props;
	struct backlight_device *bdev;
	u8 ver_major, ver_minor, ver_release;
	int ret = -ENXIO;

	gmux_data = kzalloc(sizeof(*gmux_data), GFP_KERNEL);
	if (!gmux_data)
	return -ENOMEM;
	pnp_set_drvdata(pnp, gmux_data);

	res = pnp_get_resource(pnp, IORESOURCE_IO, 0);
	if (!res) {
	pr_err("Failed to find gmux I/O resource\n");
	goto err_free;
	}

	gmux_data->iostart = res->start;
	gmux_data->iolen = res->end - res->start;

	if (gmux_data->iolen < GMUX_MIN_IO_LEN) {
	pr_err("gmux I/O region too small (%lu < %u)\n",
	gmux_data->iolen, GMUX_MIN_IO_LEN);
	goto err_free;
	}

	if (!request_region(gmux_data->iostart, gmux_data->iolen,
	"Apple gmux")) {
	pr_err("gmux I/O already in use\n");
	goto err_free;
	}

	/*
	* Invalid version information may indicate either that the gmux
	* device isn't present or that it's a new one that uses indexed
	* io
	*/

	ver_major = gmux_read8(gmux_data, GMUX_PORT_VERSION_MAJOR);
	ver_minor = gmux_read8(gmux_data, GMUX_PORT_VERSION_MINOR);
	ver_release = gmux_read8(gmux_data, GMUX_PORT_VERSION_RELEASE);
	if (ver_major == 0xff && ver_minor == 0xff && ver_release == 0xff) {
	if (gmux_is_indexed(gmux_data)) {
	mutex_init(&gmux_data->index_lock);
	gmux_data->indexed = true;
	} else {
	pr_info("gmux device not present\n");
	ret = -ENODEV;
	goto err_release;
	}
	pr_info("Found indexed gmux\n");
	} else {
	pr_info("Found gmux version %d.%d.%d\n", ver_major, ver_minor,
	ver_release);
	}

	memset(&props, 0, sizeof(props));
	props.type = BACKLIGHT_PLATFORM;
	props.max_brightness = gmux_read32(gmux_data, GMUX_PORT_MAX_BRIGHTNESS);

	/*
	* Currently it's assumed that the maximum brightness is less than
	* 2^24 for compatibility with old gmux versions. Cap the max
	* brightness at this value, but print a warning if the hardware
	* reports something higher so that it can be fixed.
	*/
	if (WARN_ON(props.max_brightness > GMUX_MAX_BRIGHTNESS))
	props.max_brightness = GMUX_MAX_BRIGHTNESS;

	bdev = backlight_device_register("gmux_backlight", &pnp->dev,
	gmux_data, &gmux_bl_ops, &props);
	if (IS_ERR(bdev)) {
	ret = PTR_ERR(bdev);
	goto err_release;
	}

	gmux_data->bdev = bdev;
	bdev->props.brightness = gmux_get_brightness(bdev);
	backlight_update_status(bdev);

	/*
	* The backlight situation on Macs is complicated. If the gmux is
	* present it's the best choice, because it always works for
	* backlight control and supports more levels than other options.
	* Disable the other backlight choices.
	*/
	acpi_video_dmi_promote_vendor();
	#if defined (CONFIG_ACPI_VIDEO) \|\| defined (CONFIG_ACPI_VIDEO_MODULE)
	acpi_video_unregister();
	#endif
	apple_bl_unregister();

	return 0;

	err_release:
	release_region(gmux_data->iostart, gmux_data->iolen);
	err_free:
	kfree(gmux_data);
	return ret;
	}

	static void __devexit gmux_remove(struct pnp_dev *pnp)
	{
	struct apple_gmux_data *gmux_data = pnp_get_drvdata(pnp);

	backlight_device_unregister(gmux_data->bdev);
	release_region(gmux_data->iostart, gmux_data->iolen);
	kfree(gmux_data);

	acpi_video_dmi_demote_vendor();
	#if defined (CONFIG_ACPI_VIDEO) \|\| defined (CONFIG_ACPI_VIDEO_MODULE)
	acpi_video_register();
	#endif
	apple_bl_register();
	}

	static const struct pnp_device_id gmux_device_ids[] = {
	{"APP000B", 0},
	{"", 0}
	};

	static struct pnp_driver gmux_pnp_driver = {
	.name = "apple-gmux",
	.probe = gmux_probe,
	.remove = __devexit_p(gmux_remove),
	.id_table = gmux_device_ids,
	};

	static int __init apple_gmux_init(void)
	{
	return pnp_register_driver(&gmux_pnp_driver);
	}

	static void __exit apple_gmux_exit(void)
	{
	pnp_unregister_driver(&gmux_pnp_driver);
	}

	module_init(apple_gmux_init);
	module_exit(apple_gmux_exit);

	MODULE_AUTHOR("Seth Forshee <seth.forshee@canonical.com>");
	MODULE_DESCRIPTION("Apple Gmux Driver");
	MODULE_LICENSE("GPL");
	MODULE_DEVICE_TABLE(pnp, gmux_device_ids);