3 files changed, 255 insertions, 0 deletions

diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
index ce10f0313961..c5b4bfed7bb4 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 dcfee6b2606d..bf7e4f935b17 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 000000000000..8a582bdfdc76
--- /dev/null
+++ b/drivers/platform/x86/apple-gmux.c
@@ -0,0 +1,244 @@
+/*
+ *  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 <acpi/video.h>
+#include <asm/io.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);