platform/chrome: Add Chrome OS keyboard backlight LEDs support

This is a driver for ACPI-based keyboard backlight LEDs found on
Chromebooks. The driver locates \\_SB.KBLT ACPI device and exports
backlight as "chromeos::kbd_backlight" LED class device in sysfs.

Signed-off-by: Simon Que <sque@chromium.org>
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Tested-by: Evan McClain <aeroevan@gmail.com>
Signed-off-by: Dmitry Torokhov <dtor@chromium.org>
Signed-off-by: Olof Johansson <olof@lixom.net>

3 files changed, 140 insertions, 7 deletions

diff --git a/drivers/platform/chrome/Kconfig b/drivers/platform/chrome/Kconfig
index d03df4a60d05..76bdae1a93bb 100644
--- a/drivers/platform/chrome/Kconfig
+++ b/drivers/platform/chrome/Kconfig
@@ -64,4 +64,14 @@ config CROS_EC_PROTO
         help
           ChromeOS EC communication protocol helpers.
 
+config CROS_KBD_LED_BACKLIGHT
+        tristate "Backlight LED support for Chrome OS keyboards"
+        depends on LEDS_CLASS && ACPI
+        help
+          This option enables support for the keyboard backlight LEDs on
+          select Chrome OS systems.
+
+          To compile this driver as a module, choose M here: the
+          module will be called cros_kbd_led_backlight.
+
 endif # CHROMEOS_PLATFORMS
diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
index bc498bda8211..4f3462783a3c 100644
--- a/drivers/platform/chrome/Makefile
+++ b/drivers/platform/chrome/Makefile
@@ -1,8 +1,9 @@
 
-obj-$(CONFIG_CHROMEOS_LAPTOP)   += chromeos_laptop.o
-obj-$(CONFIG_CHROMEOS_PSTORE)   += chromeos_pstore.o
-cros_ec_devs-objs               := cros_ec_dev.o cros_ec_sysfs.o \
-                                   cros_ec_lightbar.o cros_ec_vbc.o
-obj-$(CONFIG_CROS_EC_CHARDEV)   += cros_ec_devs.o
-obj-$(CONFIG_CROS_EC_LPC)       += cros_ec_lpc.o
-obj-$(CONFIG_CROS_EC_PROTO)     += cros_ec_proto.o
+obj-$(CONFIG_CHROMEOS_LAPTOP)           += chromeos_laptop.o
+obj-$(CONFIG_CHROMEOS_PSTORE)           += chromeos_pstore.o
+cros_ec_devs-objs                       := cros_ec_dev.o cros_ec_sysfs.o \
+                                           cros_ec_lightbar.o cros_ec_vbc.o
+obj-$(CONFIG_CROS_EC_CHARDEV)           += cros_ec_devs.o
+obj-$(CONFIG_CROS_EC_LPC)               += cros_ec_lpc.o
+obj-$(CONFIG_CROS_EC_PROTO)             += cros_ec_proto.o
+obj-$(CONFIG_CROS_KBD_LED_BACKLIGHT)    += cros_kbd_led_backlight.o
diff --git a/drivers/platform/chrome/cros_kbd_led_backlight.c b/drivers/platform/chrome/cros_kbd_led_backlight.c
new file mode 100644
index 000000000000..ca3e4da852b4
--- /dev/null
+++ b/drivers/platform/chrome/cros_kbd_led_backlight.c
@@ -0,0 +1,122 @@
+/*
+ *  Keyboard backlight LED driver for Chrome OS.
+ *
+ *  Copyright (C) 2012 Google, Inc.
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ */
+
+#include <linux/acpi.h>
+#include <linux/leds.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+/* Keyboard LED ACPI Device must be defined in firmware */
+#define ACPI_KEYBOARD_BACKLIGHT_DEVICE  "\\_SB.KBLT"
+#define ACPI_KEYBOARD_BACKLIGHT_READ    ACPI_KEYBOARD_BACKLIGHT_DEVICE ".KBQC"
+#define ACPI_KEYBOARD_BACKLIGHT_WRITE   ACPI_KEYBOARD_BACKLIGHT_DEVICE ".KBCM"
+
+#define ACPI_KEYBOARD_BACKLIGHT_MAX             100
+
+static void keyboard_led_set_brightness(struct led_classdev *cdev,
+                                        enum led_brightness brightness)
+{
+        union acpi_object param;
+        struct acpi_object_list input;
+        acpi_status status;
+
+        param.type = ACPI_TYPE_INTEGER;
+        param.integer.value = brightness;
+        input.count = 1;
+        input.pointer = &param;
+
+        status = acpi_evaluate_object(NULL, ACPI_KEYBOARD_BACKLIGHT_WRITE,
+                                      &input, NULL);
+        if (ACPI_FAILURE(status))
+                dev_err(cdev->dev, "Error setting keyboard LED value: %d\n",
+                        status);
+}
+
+static enum led_brightness
+keyboard_led_get_brightness(struct led_classdev *cdev)
+{
+        unsigned long long brightness;
+        acpi_status status;
+
+        status = acpi_evaluate_integer(NULL, ACPI_KEYBOARD_BACKLIGHT_READ,
+                                       NULL, &brightness);
+        if (ACPI_FAILURE(status)) {
+                dev_err(cdev->dev, "Error getting keyboard LED value: %d\n",
+                        status);
+                return -EIO;
+        }
+
+        return brightness;
+}
+
+static int keyboard_led_probe(struct platform_device *pdev)
+{
+        struct led_classdev *cdev;
+        acpi_handle handle;
+        acpi_status status;
+        int error;
+
+        /* Look for the keyboard LED ACPI Device */
+        status = acpi_get_handle(ACPI_ROOT_OBJECT,
+                                 ACPI_KEYBOARD_BACKLIGHT_DEVICE,
+                                 &handle);
+        if (ACPI_FAILURE(status)) {
+                dev_err(&pdev->dev, "Unable to find ACPI device %s: %d\n",
+                        ACPI_KEYBOARD_BACKLIGHT_DEVICE, status);
+                return -ENXIO;
+        }
+
+        cdev = devm_kzalloc(&pdev->dev, sizeof(*cdev), GFP_KERNEL);
+        if (!cdev)
+                return -ENOMEM;
+
+        cdev->name = "chromeos::kbd_backlight";
+        cdev->max_brightness = ACPI_KEYBOARD_BACKLIGHT_MAX;
+        cdev->flags |= LED_CORE_SUSPENDRESUME;
+        cdev->brightness_set = keyboard_led_set_brightness;
+        cdev->brightness_get = keyboard_led_get_brightness;
+
+        error = devm_led_classdev_register(&pdev->dev, cdev);
+        if (error)
+                return error;
+
+        return 0;
+}
+
+static const struct acpi_device_id keyboard_led_id[] = {
+        { "GOOG0002", 0 },
+        { }
+};
+MODULE_DEVICE_TABLE(acpi, keyboard_led_id);
+
+static struct platform_driver keyboard_led_driver = {
+        .driver         = {
+                .name   = "chromeos-keyboard-leds",
+                .acpi_match_table = ACPI_PTR(keyboard_led_id),
+        },
+        .probe          = keyboard_led_probe,
+};
+module_platform_driver(keyboard_led_driver);
+
+MODULE_AUTHOR("Simon Que <sque@chromium.org>");
+MODULE_DESCRIPTION("ChromeOS Keyboard backlight LED Driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:chromeos-keyboard-leds");