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Linux kernel mirror (for testing)
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linux
1// SPDX-License-Identifier: GPL-2.0
2
3/*
4 * ChromeOS Privacy Screen support
5 *
6 * Copyright (C) 2022 Google LLC
7 *
8 * This is the Chromeos privacy screen provider, present on certain chromebooks,
9 * represented by a GOOG0010 device in the ACPI. This ACPI device, if present,
10 * will cause the i915 drm driver to probe defer until this driver registers
11 * the privacy-screen.
12 */
13
14#include <linux/acpi.h>
15#include <linux/platform_device.h>
16#include <drm/drm_privacy_screen_driver.h>
17
18/*
19 * The DSM (Device Specific Method) constants below are the agreed API with
20 * the firmware team, on how to control privacy screen using ACPI methods.
21 */
22#define PRIV_SCRN_DSM_REVID 1 /* DSM version */
23#define PRIV_SCRN_DSM_FN_GET_STATUS 1 /* Get privacy screen status */
24#define PRIV_SCRN_DSM_FN_ENABLE 2 /* Enable privacy screen */
25#define PRIV_SCRN_DSM_FN_DISABLE 3 /* Disable privacy screen */
26
27static const guid_t chromeos_privacy_screen_dsm_guid =
28 GUID_INIT(0xc7033113, 0x8720, 0x4ceb,
29 0x90, 0x90, 0x9d, 0x52, 0xb3, 0xe5, 0x2d, 0x73);
30
31static void
32chromeos_privacy_screen_get_hw_state(struct drm_privacy_screen
33 *drm_privacy_screen)
34{
35 union acpi_object *obj;
36 struct device *privacy_screen =
37 drm_privacy_screen_get_drvdata(drm_privacy_screen);
38 acpi_handle handle = ACPI_HANDLE(privacy_screen);
39
40 obj = acpi_evaluate_dsm(handle, &chromeos_privacy_screen_dsm_guid,
41 PRIV_SCRN_DSM_REVID,
42 PRIV_SCRN_DSM_FN_GET_STATUS, NULL);
43 if (!obj) {
44 dev_err(privacy_screen,
45 "_DSM failed to get privacy-screen state\n");
46 return;
47 }
48
49 if (obj->type != ACPI_TYPE_INTEGER)
50 dev_err(privacy_screen,
51 "Bad _DSM to get privacy-screen state\n");
52 else if (obj->integer.value == 1)
53 drm_privacy_screen->hw_state = drm_privacy_screen->sw_state =
54 PRIVACY_SCREEN_ENABLED;
55 else
56 drm_privacy_screen->hw_state = drm_privacy_screen->sw_state =
57 PRIVACY_SCREEN_DISABLED;
58
59 ACPI_FREE(obj);
60}
61
62static int
63chromeos_privacy_screen_set_sw_state(struct drm_privacy_screen
64 *drm_privacy_screen,
65 enum drm_privacy_screen_status state)
66{
67 union acpi_object *obj = NULL;
68 struct device *privacy_screen =
69 drm_privacy_screen_get_drvdata(drm_privacy_screen);
70 acpi_handle handle = ACPI_HANDLE(privacy_screen);
71
72 if (state == PRIVACY_SCREEN_DISABLED) {
73 obj = acpi_evaluate_dsm(handle,
74 &chromeos_privacy_screen_dsm_guid,
75 PRIV_SCRN_DSM_REVID,
76 PRIV_SCRN_DSM_FN_DISABLE, NULL);
77 } else if (state == PRIVACY_SCREEN_ENABLED) {
78 obj = acpi_evaluate_dsm(handle,
79 &chromeos_privacy_screen_dsm_guid,
80 PRIV_SCRN_DSM_REVID,
81 PRIV_SCRN_DSM_FN_ENABLE, NULL);
82 } else {
83 dev_err(privacy_screen,
84 "Bad attempt to set privacy-screen status to %u\n",
85 state);
86 return -EINVAL;
87 }
88
89 if (!obj) {
90 dev_err(privacy_screen,
91 "_DSM failed to set privacy-screen state\n");
92 return -EIO;
93 }
94
95 drm_privacy_screen->hw_state = drm_privacy_screen->sw_state = state;
96 ACPI_FREE(obj);
97 return 0;
98}
99
100static const struct drm_privacy_screen_ops chromeos_privacy_screen_ops = {
101 .get_hw_state = chromeos_privacy_screen_get_hw_state,
102 .set_sw_state = chromeos_privacy_screen_set_sw_state,
103};
104
105static int chromeos_privacy_screen_probe(struct platform_device *pdev)
106{
107 struct drm_privacy_screen *drm_privacy_screen =
108 drm_privacy_screen_register(&pdev->dev,
109 &chromeos_privacy_screen_ops,
110 &pdev->dev);
111
112 if (IS_ERR(drm_privacy_screen)) {
113 dev_err(&pdev->dev, "Error registering privacy-screen\n");
114 return PTR_ERR(drm_privacy_screen);
115 }
116
117 platform_set_drvdata(pdev, drm_privacy_screen);
118 dev_info(&pdev->dev, "registered privacy-screen '%s'\n",
119 dev_name(&drm_privacy_screen->dev));
120
121 return 0;
122}
123
124static void chromeos_privacy_screen_remove(struct platform_device *pdev)
125{
126 drm_privacy_screen_unregister(platform_get_drvdata(pdev));
127}
128
129static const struct acpi_device_id chromeos_privacy_screen_device_ids[] = {
130 {"GOOG0010", 0}, /* Google's electronic privacy screen for eDP-1 */
131 {}
132};
133MODULE_DEVICE_TABLE(acpi, chromeos_privacy_screen_device_ids);
134
135static struct platform_driver chromeos_privacy_screen_driver = {
136 .probe = chromeos_privacy_screen_probe,
137 .remove = chromeos_privacy_screen_remove,
138 .driver = {
139 .name = "chromeos_privacy_screen_driver",
140 .acpi_match_table = chromeos_privacy_screen_device_ids,
141 },
142};
143
144module_platform_driver(chromeos_privacy_screen_driver);
145MODULE_LICENSE("GPL v2");
146MODULE_DESCRIPTION("ChromeOS ACPI Privacy Screen driver");
147MODULE_AUTHOR("Rajat Jain <rajatja@google.com>");