[PATCH] platform/chrome: Add Chrome OS keyboard backlight LEDs support

From: Dmitry Torokhov
Date: Fri Mar 04 2016 - 20:23:19 EST


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@xxxxxxxxxxxx>
Signed-off-by: Duncan Laurie <dlaurie@xxxxxxxxxxxx>
Signed-off-by: Dmitry Torokhov <dtor@xxxxxxxxxxxx>
---

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(-)

diff --git a/drivers/platform/chrome/Kconfig b/drivers/platform/chrome/Kconfig
index d03df4a..76bdae1 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 bc498bd..4f34627 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 0000000..55477d7
--- /dev/null
+++ b/drivers/platform/chrome/cros_kbd_led_backlight.c
@@ -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";
+ 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;
+
+ platform_set_drvdata(pdev, cdev);
+ 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@xxxxxxxxxxxx>");
+MODULE_DESCRIPTION("ChromeOS Keyboard backlight LED Driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:chromeos-keyboard-leds");
--
2.7.0.rc3.207.g0ac5344


--
Dmitry