drivers/platform/chrome/chromeos_privacy_screen.c

Source file repositories/reference/linux-study-clean/drivers/platform/chrome/chromeos_privacy_screen.c

File Facts

System
Linux kernel
Corpus path
drivers/platform/chrome/chromeos_privacy_screen.c
Extension
.c
Size
4510 bytes
Lines
151
Domain
Driver Families
Bucket
drivers/platform
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

// 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 <linux/platform_device.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;
	struct device *privacy_screen =
		drm_privacy_screen_get_drvdata(drm_privacy_screen);
	acpi_handle handle = ACPI_HANDLE(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;
	struct device *privacy_screen =
		drm_privacy_screen_get_drvdata(drm_privacy_screen);
	acpi_handle handle = ACPI_HANDLE(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,

Annotation

Implementation Notes