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 <drm/drm_privacy_screen_driver.h>
 16
 17/*
 18 * The DSM (Device Specific Method) constants below are the agreed API with
 19 * the firmware team, on how to control privacy screen using ACPI methods.
 20 */
 21#define PRIV_SCRN_DSM_REVID		1	/* DSM version */
 22#define PRIV_SCRN_DSM_FN_GET_STATUS	1	/* Get privacy screen status */
 23#define PRIV_SCRN_DSM_FN_ENABLE		2	/* Enable privacy screen */
 24#define PRIV_SCRN_DSM_FN_DISABLE	3	/* Disable privacy screen */
 25
 26static const guid_t chromeos_privacy_screen_dsm_guid =
 27		    GUID_INIT(0xc7033113, 0x8720, 0x4ceb,
 28			      0x90, 0x90, 0x9d, 0x52, 0xb3, 0xe5, 0x2d, 0x73);
 29
 30static void
 31chromeos_privacy_screen_get_hw_state(struct drm_privacy_screen
 32				     *drm_privacy_screen)
 33{
 34	union acpi_object *obj;
 35	acpi_handle handle;
 36	struct device *privacy_screen =
 37		drm_privacy_screen_get_drvdata(drm_privacy_screen);
 38
 39	handle = acpi_device_handle(to_acpi_device(privacy_screen));
 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	acpi_handle handle;
 69	struct device *privacy_screen =
 70		drm_privacy_screen_get_drvdata(drm_privacy_screen);
 71
 72	handle = acpi_device_handle(to_acpi_device(privacy_screen));
 73
 74	if (state == PRIVACY_SCREEN_DISABLED) {
 75		obj = acpi_evaluate_dsm(handle,
 76					&chromeos_privacy_screen_dsm_guid,
 77					PRIV_SCRN_DSM_REVID,
 78					PRIV_SCRN_DSM_FN_DISABLE, NULL);
 79	} else if (state == PRIVACY_SCREEN_ENABLED) {
 80		obj = acpi_evaluate_dsm(handle,
 81					&chromeos_privacy_screen_dsm_guid,
 82					PRIV_SCRN_DSM_REVID,
 83					PRIV_SCRN_DSM_FN_ENABLE, NULL);
 84	} else {
 85		dev_err(privacy_screen,
 86			"Bad attempt to set privacy-screen status to %u\n",
 87			state);
 88		return -EINVAL;
 89	}
 90
 91	if (!obj) {
 92		dev_err(privacy_screen,
 93			"_DSM failed to set privacy-screen state\n");
 94		return -EIO;
 95	}
 96
 97	drm_privacy_screen->hw_state = drm_privacy_screen->sw_state = state;
 98	ACPI_FREE(obj);
 99	return 0;
100}
101
102static const struct drm_privacy_screen_ops chromeos_privacy_screen_ops = {
103	.get_hw_state = chromeos_privacy_screen_get_hw_state,
104	.set_sw_state = chromeos_privacy_screen_set_sw_state,
105};
106
107static int chromeos_privacy_screen_add(struct acpi_device *adev)
108{
109	struct drm_privacy_screen *drm_privacy_screen =
110		drm_privacy_screen_register(&adev->dev,
111					    &chromeos_privacy_screen_ops,
112					    &adev->dev);
113
114	if (IS_ERR(drm_privacy_screen)) {
115		dev_err(&adev->dev, "Error registering privacy-screen\n");
116		return PTR_ERR(drm_privacy_screen);
117	}
118
119	adev->driver_data = drm_privacy_screen;
120	dev_info(&adev->dev, "registered privacy-screen '%s'\n",
121		 dev_name(&drm_privacy_screen->dev));
122
123	return 0;
124}
125
126static void chromeos_privacy_screen_remove(struct acpi_device *adev)
127{
128	struct drm_privacy_screen *drm_privacy_screen =	acpi_driver_data(adev);
129
130	drm_privacy_screen_unregister(drm_privacy_screen);
131}
132
133static const struct acpi_device_id chromeos_privacy_screen_device_ids[] = {
134	{"GOOG0010", 0}, /* Google's electronic privacy screen for eDP-1 */
135	{}
136};
137MODULE_DEVICE_TABLE(acpi, chromeos_privacy_screen_device_ids);
138
139static struct acpi_driver chromeos_privacy_screen_driver = {
140	.name = "chromeos_privacy_screen_driver",
141	.class = "ChromeOS",
142	.ids = chromeos_privacy_screen_device_ids,
143	.ops = {
144		.add = chromeos_privacy_screen_add,
145		.remove = chromeos_privacy_screen_remove,
146	},
147};
148
149module_acpi_driver(chromeos_privacy_screen_driver);
150MODULE_LICENSE("GPL v2");
151MODULE_DESCRIPTION("ChromeOS ACPI Privacy Screen driver");
152MODULE_AUTHOR("Rajat Jain <rajatja@google.com>");