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 
14 /**
15  * wmi_brightness_notify() - helper function for calling WMI-wrapped ACPI method
16  * @w:    Pointer to the struct wmi_device identified by %WMI_BRIGHTNESS_GUID
17  * @id:   The WMI method ID to call (e.g. %WMI_BRIGHTNESS_METHOD_LEVEL or
18  *        %WMI_BRIGHTNESS_METHOD_SOURCE)
19  * @mode: The operation to perform on the method (e.g. %WMI_BRIGHTNESS_MODE_SET
20  *        or %WMI_BRIGHTNESS_MODE_GET)
21  * @val:  Pointer to a value passed in by the caller when @mode is
22  *        %WMI_BRIGHTNESS_MODE_SET, or a value passed out to caller when @mode
23  *        is %WMI_BRIGHTNESS_MODE_GET or %WMI_BRIGHTNESS_MODE_GET_MAX_LEVEL.
24  *
25  * Returns 0 on success, or a negative error number on failure.
26  */
27 static int wmi_brightness_notify(struct wmi_device *w, enum wmi_brightness_method id, enum wmi_brightness_mode mode, u32 *val)
28 {
29 	struct wmi_brightness_args args = {
30 		.mode = mode,
31 		.val = 0,
32 		.ret = 0,
33 	};
34 	struct acpi_buffer buf = { (acpi_size)sizeof(args), &args };
35 	acpi_status status;
36 
37 	if (id < WMI_BRIGHTNESS_METHOD_LEVEL ||
38 	    id >= WMI_BRIGHTNESS_METHOD_MAX ||
39 	    mode < WMI_BRIGHTNESS_MODE_GET || mode >= WMI_BRIGHTNESS_MODE_MAX)
40 		return -EINVAL;
41 
42 	if (mode == WMI_BRIGHTNESS_MODE_SET)
43 		args.val = *val;
44 
45 	status = wmidev_evaluate_method(w, 0, id, &buf, &buf);
46 	if (ACPI_FAILURE(status)) {
47 		dev_err(&w->dev, "EC backlight control failed: %s\n",
48 			acpi_format_exception(status));
49 		return -EIO;
50 	}
51 
52 	if (mode != WMI_BRIGHTNESS_MODE_SET)
53 		*val = args.ret;
54 
55 	return 0;
56 }
57 
58 static int nvidia_wmi_ec_backlight_update_status(struct backlight_device *bd)
59 {
60 	struct wmi_device *wdev = bl_get_data(bd);
61 
62 	return wmi_brightness_notify(wdev, WMI_BRIGHTNESS_METHOD_LEVEL,
63 	                             WMI_BRIGHTNESS_MODE_SET,
64 			             &bd->props.brightness);
65 }
66 
67 static int nvidia_wmi_ec_backlight_get_brightness(struct backlight_device *bd)
68 {
69 	struct wmi_device *wdev = bl_get_data(bd);
70 	u32 level;
71 	int ret;
72 
73 	ret = wmi_brightness_notify(wdev, WMI_BRIGHTNESS_METHOD_LEVEL,
74 	                            WMI_BRIGHTNESS_MODE_GET, &level);
75 	if (ret < 0)
76 		return ret;
77 
78 	return level;
79 }
80 
81 static const struct backlight_ops nvidia_wmi_ec_backlight_ops = {
82 	.update_status = nvidia_wmi_ec_backlight_update_status,
83 	.get_brightness = nvidia_wmi_ec_backlight_get_brightness,
84 };
85 
86 static int nvidia_wmi_ec_backlight_probe(struct wmi_device *wdev, const void *ctx)
87 {
88 	struct backlight_properties props = {};
89 	struct backlight_device *bdev;
90 	u32 source;
91 	int ret;
92 
93 	ret = wmi_brightness_notify(wdev, WMI_BRIGHTNESS_METHOD_SOURCE,
94 	                           WMI_BRIGHTNESS_MODE_GET, &source);
95 	if (ret)
96 		return ret;
97 
98 	/*
99 	 * This driver is only to be used when brightness control is handled
100 	 * by the EC; otherwise, the GPU driver(s) should control brightness.
101 	 */
102 	if (source != WMI_BRIGHTNESS_SOURCE_EC)
103 		return -ENODEV;
104 
105 	/*
106 	 * Identify this backlight device as a firmware device so that it can
107 	 * be prioritized over any exposed GPU-driven raw device(s).
108 	 */
109 	props.type = BACKLIGHT_FIRMWARE;
110 
111 	ret = wmi_brightness_notify(wdev, WMI_BRIGHTNESS_METHOD_LEVEL,
112 	                           WMI_BRIGHTNESS_MODE_GET_MAX_LEVEL,
113 	                           &props.max_brightness);
114 	if (ret)
115 		return ret;
116 
117 	ret = wmi_brightness_notify(wdev, WMI_BRIGHTNESS_METHOD_LEVEL,
118 	                           WMI_BRIGHTNESS_MODE_GET, &props.brightness);
119 	if (ret)
120 		return ret;
121 
122 	bdev = devm_backlight_device_register(&wdev->dev,
123 	                                      "nvidia_wmi_ec_backlight",
124 					      &wdev->dev, wdev,
125 					      &nvidia_wmi_ec_backlight_ops,
126 					      &props);
127 	return PTR_ERR_OR_ZERO(bdev);
128 }
129 
130 static const struct wmi_device_id nvidia_wmi_ec_backlight_id_table[] = {
131 	{ .guid_string = WMI_BRIGHTNESS_GUID },
132 	{ }
133 };
134 MODULE_DEVICE_TABLE(wmi, nvidia_wmi_ec_backlight_id_table);
135 
136 static struct wmi_driver nvidia_wmi_ec_backlight_driver = {
137 	.driver = {
138 		.name = "nvidia-wmi-ec-backlight",
139 	},
140 	.probe = nvidia_wmi_ec_backlight_probe,
141 	.id_table = nvidia_wmi_ec_backlight_id_table,
142 };
143 module_wmi_driver(nvidia_wmi_ec_backlight_driver);
144 
145 MODULE_AUTHOR("Daniel Dadap <ddadap@nvidia.com>");
146 MODULE_DESCRIPTION("NVIDIA WMI EC Backlight driver");
147 MODULE_LICENSE("GPL");
148