1 // SPDX-License-Identifier: GPL-2.0+
2 // Keyboard backlight LED driver for ChromeOS
3 //
4 // Copyright (C) 2012 Google, Inc.
5 
6 #include <linux/acpi.h>
7 #include <linux/leds.h>
8 #include <linux/delay.h>
9 #include <linux/err.h>
10 #include <linux/module.h>
11 #include <linux/init.h>
12 #include <linux/kernel.h>
13 #include <linux/platform_device.h>
14 #include <linux/slab.h>
15 
16 /* Keyboard LED ACPI Device must be defined in firmware */
17 #define ACPI_KEYBOARD_BACKLIGHT_DEVICE	"\\_SB.KBLT"
18 #define ACPI_KEYBOARD_BACKLIGHT_READ	ACPI_KEYBOARD_BACKLIGHT_DEVICE ".KBQC"
19 #define ACPI_KEYBOARD_BACKLIGHT_WRITE	ACPI_KEYBOARD_BACKLIGHT_DEVICE ".KBCM"
20 
21 #define ACPI_KEYBOARD_BACKLIGHT_MAX		100
22 
23 static void keyboard_led_set_brightness(struct led_classdev *cdev,
24 					enum led_brightness brightness)
25 {
26 	union acpi_object param;
27 	struct acpi_object_list input;
28 	acpi_status status;
29 
30 	param.type = ACPI_TYPE_INTEGER;
31 	param.integer.value = brightness;
32 	input.count = 1;
33 	input.pointer = &param;
34 
35 	status = acpi_evaluate_object(NULL, ACPI_KEYBOARD_BACKLIGHT_WRITE,
36 				      &input, NULL);
37 	if (ACPI_FAILURE(status))
38 		dev_err(cdev->dev, "Error setting keyboard LED value: %d\n",
39 			status);
40 }
41 
42 static enum led_brightness
43 keyboard_led_get_brightness(struct led_classdev *cdev)
44 {
45 	unsigned long long brightness;
46 	acpi_status status;
47 
48 	status = acpi_evaluate_integer(NULL, ACPI_KEYBOARD_BACKLIGHT_READ,
49 				       NULL, &brightness);
50 	if (ACPI_FAILURE(status)) {
51 		dev_err(cdev->dev, "Error getting keyboard LED value: %d\n",
52 			status);
53 		return -EIO;
54 	}
55 
56 	return brightness;
57 }
58 
59 static int keyboard_led_probe(struct platform_device *pdev)
60 {
61 	struct led_classdev *cdev;
62 	acpi_handle handle;
63 	acpi_status status;
64 	int error;
65 
66 	/* Look for the keyboard LED ACPI Device */
67 	status = acpi_get_handle(ACPI_ROOT_OBJECT,
68 				 ACPI_KEYBOARD_BACKLIGHT_DEVICE,
69 				 &handle);
70 	if (ACPI_FAILURE(status)) {
71 		dev_err(&pdev->dev, "Unable to find ACPI device %s: %d\n",
72 			ACPI_KEYBOARD_BACKLIGHT_DEVICE, status);
73 		return -ENXIO;
74 	}
75 
76 	cdev = devm_kzalloc(&pdev->dev, sizeof(*cdev), GFP_KERNEL);
77 	if (!cdev)
78 		return -ENOMEM;
79 
80 	cdev->name = "chromeos::kbd_backlight";
81 	cdev->max_brightness = ACPI_KEYBOARD_BACKLIGHT_MAX;
82 	cdev->flags |= LED_CORE_SUSPENDRESUME;
83 	cdev->brightness_set = keyboard_led_set_brightness;
84 	cdev->brightness_get = keyboard_led_get_brightness;
85 
86 	error = devm_led_classdev_register(&pdev->dev, cdev);
87 	if (error)
88 		return error;
89 
90 	return 0;
91 }
92 
93 static const struct acpi_device_id keyboard_led_id[] = {
94 	{ "GOOG0002", 0 },
95 	{ }
96 };
97 MODULE_DEVICE_TABLE(acpi, keyboard_led_id);
98 
99 static struct platform_driver keyboard_led_driver = {
100 	.driver		= {
101 		.name	= "chromeos-keyboard-leds",
102 		.acpi_match_table = ACPI_PTR(keyboard_led_id),
103 	},
104 	.probe		= keyboard_led_probe,
105 };
106 module_platform_driver(keyboard_led_driver);
107 
108 MODULE_AUTHOR("Simon Que <sque@chromium.org>");
109 MODULE_DESCRIPTION("ChromeOS Keyboard backlight LED Driver");
110 MODULE_LICENSE("GPL");
111 MODULE_ALIAS("platform:chromeos-keyboard-leds");
112