drivers/platform/chrome/chromeos_privacy_screen.c

   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
  26 static const guid_t chromeos_privacy_screen_dsm_guid =
  27                     GUID_INIT(0xc7033113, 0x8720, 0x4ceb,
  28                               0x90, 0x90, 0x9d, 0x52, 0xb3, 0xe5, 0x2d, 0x73);
  29
  30 static void
  31 chromeos_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
  62 static int
  63 chromeos_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
 102 static 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
 107 static 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
 126 static 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
 133 static const struct acpi_device_id chromeos_privacy_screen_device_ids[] = {
 134         {"GOOG0010", 0}, /* Google's electronic privacy screen for eDP-1 */
 135         {}
 136 };
 137 MODULE_DEVICE_TABLE(acpi, chromeos_privacy_screen_device_ids);
 138
 139 static 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
 149 module_acpi_driver(chromeos_privacy_screen_driver);
 150 MODULE_LICENSE("GPL v2");
 151 MODULE_DESCRIPTION("ChromeOS ACPI Privacy Screen driver");
 152 MODULE_AUTHOR("Rajat Jain <rajatja@google.com>");