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 <[email protected]>

Signed-off-by Duncan Laurie <[email protected]>

Signed-off-by Dmitry Torokhov <[email protected]>

---

Changes form previous submission:

- moved from drivers/leds to drivers/platform/chrome
- added method to retrieve brightness from ACPI
- renamed to cros_kbd_led_backlight
- config option renamed to CROS_KBD_LED_BACKLIGHT
- no longer setting initial brightness to max brightness (although on Pixel 1 - Link - ACPI initially reports 100 as brightness anyway)

I ran this on Pixel 1; Evan, could you give it a spin on your Pixel 2?

Thanks!

 drivers/platform/chrome/Kconfig                  |  10 ++
 drivers/platform/chrome/Makefile                 |  15 +--
 drivers/platform/chrome/cros_kbd_led_backlight.c | 123 +++++++++++++++++++++++
 3 files changed, 141 insertions(+), 7 deletions(-)

drivers/platform/chrome/Kconfig +10 -0

index d03df4a..76bdae1 100644
@@ -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

drivers/platform/chrome/Makefile +8 -7

index bc498bd..4f34627 100644
@@ -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

drivers/platform/chrome/cros_kbd_led_backlight.c new file +91 -0

new file mode 100644
index 0000000..55477d7
@@ -0,0 +1,123 @@
+/*
+ *  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";

drivers/platform/chrome/cros_kbd_led_backlight.c new file +22 -1

+       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 <[email protected]>");
+MODULE_DESCRIPTION("ChromeOS Keyboard backlight LED Driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:chromeos-keyboard-leds");
--

2.7.0.rc3.207.g0ac5344

--
Dmitry

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 <[email protected]>

Signed-off-by Duncan Laurie <[email protected]>

Signed-off-by Dmitry Torokhov <[email protected]>

---

Changes form previous submission:

- moved from drivers/leds to drivers/platform/chrome
- added method to retrieve brightness from ACPI
- renamed to cros_kbd_led_backlight
- config option renamed to CROS_KBD_LED_BACKLIGHT
- no longer setting initial brightness to max brightness (although on Pixel 1 - Link - ACPI initially reports 100 as brightness anyway)

I ran this on Pixel 1; Evan, could you give it a spin on your Pixel 2?