backlight: Add Nvidia-based Apple Macbook Pro backlight driver

Nvidia-based Apple Macbook Pros don't appear to handle backlight control
through the graphics card registers or ACPI, but instead trigger changes
via SMI calls. This driver registers a generic backlight device that
lets existing userspace deal with it. Code derived from Julien Blache's
Pommed application.
Signed-off-by: Julien Blache <jb@jblache.org>
Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Richard Purdie <rpurdie@rpsys.net>

drivers/video/backlight/Kconfig

@@ -119,3 +119,12 @@ config BACKLIGHT_PWM
 	help
 	  If you have a LCD backlight adjustable by PWM, say Y to enable
 	  this driver.
+
+config BACKLIGHT_MBP_NVIDIA
+       tristate "MacBook Pro Nvidia Backlight Driver"
+       depends on BACKLIGHT_CLASS_DEVICE && X86
+       default n
+       help
+         If you have an Apple Macbook Pro with Nvidia graphics hardware say Y
+	 to enable a driver for its backlight
+

drivers/video/backlight/Makefile

@@ -11,3 +11,5 @@ obj-$(CONFIG_BACKLIGHT_OMAP1)	+= omap1_bl.o
 obj-$(CONFIG_BACKLIGHT_PROGEAR) += progear_bl.o
 obj-$(CONFIG_BACKLIGHT_CARILLO_RANCH) += cr_bllcd.o
 obj-$(CONFIG_BACKLIGHT_PWM)	+= pwm_bl.o
+obj-$(CONFIG_BACKLIGHT_MBP_NVIDIA) += mbp_nvidia_bl.o
+

drivers/video/backlight/mbp_nvidia_bl.c

+/*
+ *  Backlight Driver for Nvidia 8600 in Macbook Pro
+ *
+ *  Copyright (c) Red Hat <mjg@redhat.com>
+ *  Based on code from Pommed:
+ *  Copyright (C) 2006 Nicolas Boichat <nicolas @boichat.ch>
+ *  Copyright (C) 2006 Felipe Alfaro Solana <felipe_alfaro @linuxmail.org>
+ *  Copyright (C) 2007 Julien BLACHE <jb@jblache.org>
+ *
+ *  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.
+ *
+ *  This driver triggers SMIs which cause the firmware to change the
+ *  backlight brightness. This is icky in many ways, but it's impractical to
+ *  get at the firmware code in order to figure out what it's actually doing.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/platform_device.h>
+#include <linux/backlight.h>
+#include <linux/err.h>
+#include <linux/dmi.h>
+#include <linux/io.h>
+
+static struct backlight_device *mbp_backlight_device;
+
+static struct dmi_system_id __initdata mbp_device_table[] = {
+	{
+		.ident = "3,1",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
+			DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro3,1"),
+		},
+	},
+	{
+		.ident = "3,2",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
+			DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro3,2"),
+		},
+	},
+	{
+		.ident = "4,1",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
+			DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro4,1"),
+		},
+	},
+	{ }
+};
+
+static int mbp_send_intensity(struct backlight_device *bd)
+{
+	int intensity = bd->props.brightness;
+
+	outb(0x04 | (intensity << 4), 0xb3);
+	outb(0xbf, 0xb2);
+
+	return 0;
+}
+
+static int mbp_get_intensity(struct backlight_device *bd)
+{
+	outb(0x03, 0xb3);
+	outb(0xbf, 0xb2);
+	return inb(0xb3) >> 4;
+}
+
+static struct backlight_ops mbp_ops = {
+	.get_brightness = mbp_get_intensity,
+	.update_status  = mbp_send_intensity,
+};
+
+static int __init mbp_init(void)
+{
+	if (!dmi_check_system(mbp_device_table))
+		return -ENODEV;
+
+	if (!request_region(0xb2, 2, "Macbook Pro backlight"))
+		return -ENXIO;
+
+	mbp_backlight_device = backlight_device_register("mbp_backlight",
+							 NULL, NULL,
+							 &mbp_ops);
+	if (IS_ERR(mbp_backlight_device)) {
+		release_region(0xb2, 2);
+		return PTR_ERR(mbp_backlight_device);
+	}
+
+	mbp_backlight_device->props.max_brightness = 15;
+	mbp_backlight_device->props.brightness =
+		mbp_get_intensity(mbp_backlight_device);
+	backlight_update_status(mbp_backlight_device);
+
+	return 0;
+}
+
+static void __exit mbp_exit(void)
+{
+	backlight_device_unregister(mbp_backlight_device);
+
+	release_region(0xb2, 2);
+}
+
+module_init(mbp_init);
+module_exit(mbp_exit);
+
+MODULE_AUTHOR("Matthew Garrett <mjg@redhat.com>");
+MODULE_DESCRIPTION("Nvidia-based Macbook Pro Backlight Driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("svnAppleInc.:pnMacBookPro3,1");
+MODULE_ALIAS("svnAppleInc.:pnMacBookPro3,2");
+MODULE_ALIAS("svnAppleInc.:pnMacBookPro4,1");