drivers/platform/chrome/chromeos_tbmc.c

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

File Facts

System
Linux kernel
Corpus path
drivers/platform/chrome/chromeos_tbmc.c
Extension
.c
Size
3574 bytes
Lines
143
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
// Driver to detect Tablet Mode for ChromeOS convertible.
//
// Copyright (C) 2017 Google, Inc.
// Author: Gwendal Grignou <gwendal@chromium.org>
//
// On Chromebook using ACPI, this device listens for notification
// from GOOG0006 and issue method TBMC to retrieve the status.
//
// GOOG0006 issues the notification when it receives EC_HOST_EVENT_MODE_CHANGE
// from the EC.
// Method TBMC reads EC_ACPI_MEM_DEVICE_ORIENTATION byte from the shared
// memory region.

#include <linux/acpi.h>
#include <linux/input.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/printk.h>

#define DRV_NAME "chromeos_tbmc"
#define ACPI_DRV_NAME "GOOG0006"

static int chromeos_tbmc_query_switch(struct acpi_device *adev,
				     struct input_dev *idev)
{
	unsigned long long state;
	acpi_status status;

	status = acpi_evaluate_integer(adev->handle, "TBMC", NULL, &state);
	if (ACPI_FAILURE(status))
		return -ENODEV;

	/* input layer checks if event is redundant */
	input_report_switch(idev, SW_TABLET_MODE, state);
	input_sync(idev);

	return 0;
}

static __maybe_unused int chromeos_tbmc_resume(struct device *dev)
{
	return chromeos_tbmc_query_switch(ACPI_COMPANION(dev), dev_get_drvdata(dev));
}

static void chromeos_tbmc_notify(acpi_handle handle, u32 event, void *data)
{
	struct device *dev = data;

	acpi_pm_wakeup_event(dev);
	switch (event) {
	case 0x80:
		chromeos_tbmc_query_switch(ACPI_COMPANION(dev), dev_get_drvdata(dev));
		break;
	default:
		dev_err(dev, "Unexpected event: 0x%08X\n", event);
	}
}

static int chromeos_tbmc_open(struct input_dev *idev)
{
	struct acpi_device *adev = input_get_drvdata(idev);

	return chromeos_tbmc_query_switch(adev, idev);
}

static int chromeos_tbmc_probe(struct platform_device *pdev)
{
	struct input_dev *idev;
	struct device *dev = &pdev->dev;
	struct acpi_device *adev;
	int ret;

	adev = ACPI_COMPANION(dev);
	if (!adev)
		return -ENODEV;

	idev = devm_input_allocate_device(dev);
	if (!idev)
		return -ENOMEM;

	idev->name = "Tablet Mode Switch";
	idev->phys = acpi_device_hid(adev);

	idev->id.bustype = BUS_HOST;
	idev->id.version = 1;
	idev->id.product = 0;
	idev->open = chromeos_tbmc_open;

Annotation

Implementation Notes