1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (c) 2020, NVIDIA CORPORATION.  All rights reserved.
4  */
5 
6 #include <linux/acpi.h>
7 #include <linux/backlight.h>
8 #include <linux/mod_devicetable.h>
9 #include <linux/module.h>
10 #include <linux/platform_data/x86/nvidia-wmi-ec-backlight.h>
11 #include <linux/types.h>
12 #include <linux/wmi.h>
13 #include <acpi/video.h>
14 
15 static bool force;
16 module_param(force, bool, 0444);
17 MODULE_PARM_DESC(force, "Force loading (disable acpi_backlight=xxx checks");
18 
19 /**
20  * wmi_brightness_notify() - helper function for calling WMI-wrapped ACPI method
21  * @w:    Pointer to the struct wmi_device identified by %WMI_BRIGHTNESS_GUID
22  * @id:   The WMI method ID to call (e.g. %WMI_BRIGHTNESS_METHOD_LEVEL or
23  *        %WMI_BRIGHTNESS_METHOD_SOURCE)
24  * @mode: The operation to perform on the method (e.g. %WMI_BRIGHTNESS_MODE_SET
25  *        or %WMI_BRIGHTNESS_MODE_GET)
26  * @val:  Pointer to a value passed in by the caller when @mode is
27  *        %WMI_BRIGHTNESS_MODE_SET, or a value passed out to caller when @mode
28  *        is %WMI_BRIGHTNESS_MODE_GET or %WMI_BRIGHTNESS_MODE_GET_MAX_LEVEL.
29  *
30  * Returns 0 on success, or a negative error number on failure.
31  */
32 static int wmi_brightness_notify(struct wmi_device *w, enum wmi_brightness_method id, enum wmi_brightness_mode mode, u32 *val)
33 {
34 	struct wmi_brightness_args args = {
35 		.mode = mode,
36 		.val = 0,
37 		.ret = 0,
38 	};
39 	struct acpi_buffer buf = { (acpi_size)sizeof(args), &args };
40 	acpi_status status;
41 
42 	if (id < WMI_BRIGHTNESS_METHOD_LEVEL ||
43 	    id >= WMI_BRIGHTNESS_METHOD_MAX ||
44 	    mode < WMI_BRIGHTNESS_MODE_GET || mode >= WMI_BRIGHTNESS_MODE_MAX)
45 		return -EINVAL;
46 
47 	if (mode == WMI_BRIGHTNESS_MODE_SET)
48 		args.val = *val;
49 
50 	status = wmidev_evaluate_method(w, 0, id, &buf, &buf);
51 	if (ACPI_FAILURE(status)) {
52 		dev_err(&w->dev, "EC backlight control failed: %s\n",
53 			acpi_format_exception(status));
54 		return -EIO;
55 	}
56 
57 	if (mode != WMI_BRIGHTNESS_MODE_SET)
58 		*val = args.ret;
59 
60 	return 0;
61 }
62 
63 static int nvidia_wmi_ec_backlight_update_status(struct backlight_device *bd)
64 {
65 	struct wmi_device *wdev = bl_get_data(bd);
66 
67 	return wmi_brightness_notify(wdev, WMI_BRIGHTNESS_METHOD_LEVEL,
68 	                             WMI_BRIGHTNESS_MODE_SET,
69 			             &bd->props.brightness);
70 }
71 
72 static int nvidia_wmi_ec_backlight_get_brightness(struct backlight_device *bd)
73 {
74 	struct wmi_device *wdev = bl_get_data(bd);
75 	u32 level;
76 	int ret;
77 
78 	ret = wmi_brightness_notify(wdev, WMI_BRIGHTNESS_METHOD_LEVEL,
79 	                            WMI_BRIGHTNESS_MODE_GET, &level);
80 	if (ret < 0)
81 		return ret;
82 
83 	return level;
84 }
85 
86 static const struct backlight_ops nvidia_wmi_ec_backlight_ops = {
87 	.update_status = nvidia_wmi_ec_backlight_update_status,
88 	.get_brightness = nvidia_wmi_ec_backlight_get_brightness,
89 };
90 
91 static int nvidia_wmi_ec_backlight_probe(struct wmi_device *wdev, const void *ctx)
92 {
93 	struct backlight_properties props = {};
94 	struct backlight_device *bdev;
95 	int ret;
96 
97 	/* drivers/acpi/video_detect.c also checks that SOURCE == EC */
98 	if (!force && acpi_video_get_backlight_type() != acpi_backlight_nvidia_wmi_ec)
99 		return -ENODEV;
100 
101 	/*
102 	 * Identify this backlight device as a firmware device so that it can
103 	 * be prioritized over any exposed GPU-driven raw device(s).
104 	 */
105 	props.type = BACKLIGHT_FIRMWARE;
106 
107 	ret = wmi_brightness_notify(wdev, WMI_BRIGHTNESS_METHOD_LEVEL,
108 	                           WMI_BRIGHTNESS_MODE_GET_MAX_LEVEL,
109 	                           &props.max_brightness);
110 	if (ret)
111 		return ret;
112 
113 	ret = wmi_brightness_notify(wdev, WMI_BRIGHTNESS_METHOD_LEVEL,
114 	                           WMI_BRIGHTNESS_MODE_GET, &props.brightness);
115 	if (ret)
116 		return ret;
117 
118 	bdev = devm_backlight_device_register(&wdev->dev,
119 	                                      "nvidia_wmi_ec_backlight",
120 					      &wdev->dev, wdev,
121 					      &nvidia_wmi_ec_backlight_ops,
122 					      &props);
123 	return PTR_ERR_OR_ZERO(bdev);
124 }
125 
126 static const struct wmi_device_id nvidia_wmi_ec_backlight_id_table[] = {
127 	{ .guid_string = WMI_BRIGHTNESS_GUID },
128 	{ }
129 };
130 MODULE_DEVICE_TABLE(wmi, nvidia_wmi_ec_backlight_id_table);
131 
132 static struct wmi_driver nvidia_wmi_ec_backlight_driver = {
133 	.driver = {
134 		.name = "nvidia-wmi-ec-backlight",
135 	},
136 	.probe = nvidia_wmi_ec_backlight_probe,
137 	.id_table = nvidia_wmi_ec_backlight_id_table,
138 };
139 module_wmi_driver(nvidia_wmi_ec_backlight_driver);
140 
141 MODULE_AUTHOR("Daniel Dadap <ddadap@nvidia.com>");
142 MODULE_DESCRIPTION("NVIDIA WMI EC Backlight driver");
143 MODULE_LICENSE("GPL");
144