Quelle  chromeos_privacy_screen.c   Sprache: C

// SPDX-License-Identifier: GPL-2.0

/*
 *  ChromeOS Privacy Screen support
 *
 * Copyright (C) 2022 Google LLC
 *
 * This is the Chromeos privacy screen provider, present on certain chromebooks,
 * represented by a GOOG0010 device in the ACPI. This ACPI device, if present,
 * will cause the i915 drm driver to probe defer until this driver registers
 * the privacy-screen.
 */

#include <linux/acpi.h>
#include <drm/drm_privacy_screen_driver.h>

/*
 * The DSM (Device Specific Method) constants below are the agreed API with
 * the firmware team, on how to control privacy screen using ACPI methods.
 */
#define PRIV_SCRN_DSM_REVID  1 /* DSM version */
#define PRIV_SCRN_DSM_FN_GET_STATUS 1 /* Get privacy screen status */
#define PRIV_SCRN_DSM_FN_ENABLE  2 /* Enable privacy screen */
#define PRIV_SCRN_DSM_FN_DISABLE 3 /* Disable privacy screen */

static const guid_t chromeos_privacy_screen_dsm_guid =
      GUID_INIT(0xc7033113, 0x8720, 0x4ceb,
         0x90, 0x90, 0x9d, 0x52, 0xb3, 0xe5, 0x2d, 0x73);

static void
chromeos_privacy_screen_get_hw_state(struct drm_privacy_screen
         *drm_privacy_screen)
{
 union acpi_object *obj;
 acpi_handle handle;
 struct device *privacy_screen =
  drm_privacy_screen_get_drvdata(drm_privacy_screen);

 handle = acpi_device_handle(to_acpi_device(privacy_screen));
 obj = acpi_evaluate_dsm(handle, &chromeos_privacy_screen_dsm_guid,
    PRIV_SCRN_DSM_REVID,
    PRIV_SCRN_DSM_FN_GET_STATUS, NULL);
 if (!obj) {
  dev_err(privacy_screen,
   "_DSM failed to get privacy-screen state\n");
  return;
 }

 if (obj->type != ACPI_TYPE_INTEGER)
  dev_err(privacy_screen,
   "Bad _DSM to get privacy-screen state\n");
 else if (obj->integer.value == 1)
  drm_privacy_screen->hw_state = drm_privacy_screen->sw_state =
   PRIVACY_SCREEN_ENABLED;
 else
  drm_privacy_screen->hw_state = drm_privacy_screen->sw_state =
   PRIVACY_SCREEN_DISABLED;

 ACPI_FREE(obj);
}

static int
chromeos_privacy_screen_set_sw_state(struct drm_privacy_screen
         *drm_privacy_screen,
         enum drm_privacy_screen_status state)
{
 union acpi_object *obj = NULL;
 acpi_handle handle;
 struct device *privacy_screen =
  drm_privacy_screen_get_drvdata(drm_privacy_screen);

 handle = acpi_device_handle(to_acpi_device(privacy_screen));

 if (state == PRIVACY_SCREEN_DISABLED) {
  obj = acpi_evaluate_dsm(handle,
     &chromeos_privacy_screen_dsm_guid,
     PRIV_SCRN_DSM_REVID,
     PRIV_SCRN_DSM_FN_DISABLE, NULL);
 } else if (state == PRIVACY_SCREEN_ENABLED) {
  obj = acpi_evaluate_dsm(handle,
     &chromeos_privacy_screen_dsm_guid,
     PRIV_SCRN_DSM_REVID,
     PRIV_SCRN_DSM_FN_ENABLE, NULL);
 } else {
  dev_err(privacy_screen,
   "Bad attempt to set privacy-screen status to %u\n",
   state);
  return -EINVAL;
 }

 if (!obj) {
  dev_err(privacy_screen,
   "_DSM failed to set privacy-screen state\n");
  return -EIO;
 }

 drm_privacy_screen->hw_state = drm_privacy_screen->sw_state = state;
 ACPI_FREE(obj);
 return 0;
}

static const struct drm_privacy_screen_ops chromeos_privacy_screen_ops = {
 .get_hw_state = chromeos_privacy_screen_get_hw_state,
 .set_sw_state = chromeos_privacy_screen_set_sw_state,
};

static int chromeos_privacy_screen_add(struct acpi_device *adev)
{
 struct drm_privacy_screen *drm_privacy_screen =
  drm_privacy_screen_register(&adev->dev,
         &chromeos_privacy_screen_ops,
         &adev->dev);

 if (IS_ERR(drm_privacy_screen)) {
  dev_err(&adev->dev, "Error registering privacy-screen\n");
  return PTR_ERR(drm_privacy_screen);
 }

 adev->driver_data = drm_privacy_screen;
 dev_info(&adev->dev, "registered privacy-screen '%s'\n",
   dev_name(&drm_privacy_screen->dev));

 return 0;
}

static void chromeos_privacy_screen_remove(struct acpi_device *adev)
{
 struct drm_privacy_screen *drm_privacy_screen = acpi_driver_data(adev);

 drm_privacy_screen_unregister(drm_privacy_screen);
}

static const struct acpi_device_id chromeos_privacy_screen_device_ids[] = {
 {"GOOG0010", 0}, /* Google's electronic privacy screen for eDP-1 */
 {}
};
MODULE_DEVICE_TABLE(acpi, chromeos_privacy_screen_device_ids);

static struct acpi_driver chromeos_privacy_screen_driver = {
 .name = "chromeos_privacy_screen_driver",
 .class = "ChromeOS",
 .ids = chromeos_privacy_screen_device_ids,
 .ops = {
  .add = chromeos_privacy_screen_add,
  .remove = chromeos_privacy_screen_remove,
 },
};

module_acpi_driver(chromeos_privacy_screen_driver);
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("ChromeOS ACPI Privacy Screen driver");
MODULE_AUTHOR("Rajat Jain ");