commit 9964e2a108292685fbbf0980493c5e9776eac762
Author: Seth Forshee <seth.forshee@canonical.com>
Date:   Fri Mar 16 14:41:21 2012 -0500

    apple_bl: Add register/unregister functions
    
    Add functions to allow other modules to enable or disable apple_bl. This
    will be used by the gmux driver to disable apple_bl when the gmux is
    present, as it is a better and more reliable option for brightness
    control.
    
    Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
    Signed-off-by: Matthew Garrett <mjg@redhat.com>

diff --git a/drivers/video/backlight/apple_bl.c b/drivers/video/backlight/apple_bl.c
index be98d15..a523b25 100644
--- a/drivers/video/backlight/apple_bl.c
+++ b/drivers/video/backlight/apple_bl.c
@@ -24,6 +24,7 @@
 #include <linux/io.h>
 #include <linux/pci.h>
 #include <linux/acpi.h>
+#include <linux/atomic.h>
 
 static struct backlight_device *apple_backlight_device;
 
@@ -221,14 +222,32 @@ static struct acpi_driver apple_bl_driver = {
 	},
 };
 
+static atomic_t apple_bl_registered = ATOMIC_INIT(0);
+
+int apple_bl_register(void)
+{
+	if (atomic_xchg(&apple_bl_registered, 1) == 0)
+		return acpi_bus_register_driver(&apple_bl_driver);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(apple_bl_register);
+
+void apple_bl_unregister(void)
+{
+	if (atomic_xchg(&apple_bl_registered, 0) == 1)
+		acpi_bus_unregister_driver(&apple_bl_driver);
+}
+EXPORT_SYMBOL_GPL(apple_bl_unregister);
+
 static int __init apple_bl_init(void)
 {
-	return acpi_bus_register_driver(&apple_bl_driver);
+	return apple_bl_register();
 }
 
 static void __exit apple_bl_exit(void)
 {
-	acpi_bus_unregister_driver(&apple_bl_driver);
+	apple_bl_unregister();
 }
 
 module_init(apple_bl_init);
diff --git a/include/linux/apple_bl.h b/include/linux/apple_bl.h
new file mode 100644
index 0000000..47bedc0
--- /dev/null
+++ b/include/linux/apple_bl.h
@@ -0,0 +1,26 @@
+/*
+ * apple_bl exported symbols
+ */
+
+#ifndef _LINUX_APPLE_BL_H
+#define _LINUX_APPLE_BL_H
+
+#ifdef CONFIG_BACKLIGHT_APPLE
+
+extern int apple_bl_register(void);
+extern void apple_bl_unregister(void);
+
+#else /* !CONFIG_BACKLIGHT_APPLE */
+
+static inline int apple_bl_register(void)
+{
+	return 0;
+}
+
+static inline void apple_bl_unregister(void)
+{
+}
+
+#endif /* !CONFIG_BACKLIGHT_APPLE */
+
+#endif /* _LINUX_APPLE_BL_H */
commit 89c093937dc8b07db4652251c83ec3710e5f15a2
Author: Seth Forshee <seth.forshee@canonical.com>
Date:   Fri Mar 16 14:41:22 2012 -0500

    platform/x86: Add driver for Apple gmux device
    
    Apple laptops with hybrid graphics have a device named gmux that
    controls the muxing of the LVDS panel between the GPUs as well as screen
    brightness. This driver adds support for the gmux device. Only backlight
    control is supported initially.
    
    Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
    Signed-off-by: Matthew Garrett <mjg@redhat.com>
    Tested-by: Grant Likely <grant.likely@secretlab.ca>

diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
index ce10f03..c5b4bfe 100644
--- a/drivers/platform/x86/Kconfig
+++ b/drivers/platform/x86/Kconfig
@@ -752,4 +752,14 @@ config SAMSUNG_Q10
 	  This driver provides support for backlight control on Samsung Q10
 	  and related laptops, including Dell Latitude X200.
 
+config APPLE_GMUX
+	tristate "Apple Gmux Driver"
+	depends on PNP
+	select BACKLIGHT_CLASS_DEVICE
+	---help---
+	  This driver provides support for the gmux device found on many
+	  Apple laptops, which controls the display mux for the hybrid
+	  graphics as well as the backlight. Currently only backlight
+	  control is supported by the driver.
+
 endif # X86_PLATFORM_DEVICES
diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
index dcfee6b..bf7e4f9 100644
--- a/drivers/platform/x86/Makefile
+++ b/drivers/platform/x86/Makefile
@@ -49,3 +49,4 @@ obj-$(CONFIG_MXM_WMI)		+= mxm-wmi.o
 obj-$(CONFIG_INTEL_MID_POWER_BUTTON)	+= intel_mid_powerbtn.o
 obj-$(CONFIG_INTEL_OAKTRAIL)	+= intel_oaktrail.o
 obj-$(CONFIG_SAMSUNG_Q10)	+= samsung-q10.o
+obj-$(CONFIG_APPLE_GMUX)	+= apple-gmux.o
diff --git a/drivers/platform/x86/apple-gmux.c b/drivers/platform/x86/apple-gmux.c
new file mode 100644
index 0000000..c81e31f
--- /dev/null
+++ b/drivers/platform/x86/apple-gmux.c
@@ -0,0 +1,242 @@
+/*
+ *  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 <acpi/video.h>
+
+struct apple_gmux_data {
+	unsigned long iostart;
+	unsigned long iolen;
+
+	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_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 inline u8 gmux_read8(struct apple_gmux_data *gmux_data, int port)
+{
+	return inb(gmux_data->iostart + port);
+}
+
+static inline void gmux_write8(struct apple_gmux_data *gmux_data, int port,
+			       u8 val)
+{
+	outb(val, gmux_data->iostart + port);
+}
+
+static inline u32 gmux_read32(struct apple_gmux_data *gmux_data, int port)
+{
+	return inl(gmux_data->iostart + port);
+}
+
+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;
+
+	/*
+	 * Older gmux versions require writing out lower bytes first then
+	 * setting the upper byte to 0 to flush the values. Newer versions
+	 * accept a single u32 write, but the old method also works, so we
+	 * just use the old method for all gmux versions.
+	 */
+	gmux_write8(gmux_data, GMUX_PORT_BRIGHTNESS, brightness);
+	gmux_write8(gmux_data, GMUX_PORT_BRIGHTNESS + 1, brightness >> 8);
+	gmux_write8(gmux_data, GMUX_PORT_BRIGHTNESS + 2, brightness >> 16);
+	gmux_write8(gmux_data, GMUX_PORT_BRIGHTNESS + 3, 0);
+
+	return 0;
+}
+
+static const struct backlight_ops gmux_bl_ops = {
+	.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;
+	}
+
+	/*
+	 * On some machines the gmux is in ACPI even thought the machine
+	 * doesn't really have a gmux. Check for invalid version information
+	 * to detect this.
+	 */
+	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) {
+		pr_info("gmux device not present\n");
+		ret = -ENODEV;
+		goto err_release;
+	}
+
+	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_unregister();
+	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_register();
+	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);