drivers/input/misc/soc_button_array.c - linux/kernel/git/bpf/bpf - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Supports for the button array on SoC tablets originally running
  * Windows 8.
  *
  * (C) Copyright 2014 Intel Corporation
  */

 #include <linux/module.h>
 #include <linux/input.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/acpi.h>
 #include <linux/gpio/consumer.h>
 #include <linux/gpio_keys.h>
 #include <linux/gpio.h>
 #include <linux/platform_device.h>

 struct soc_button_info {
 	const char *name;
 	int acpi_index;
 	unsigned int event_type;
 	unsigned int event_code;
 	bool autorepeat;
 	bool wakeup;
 };

 struct soc_device_data {
 	const struct soc_button_info *button_info;
 	int (*check)(struct device *dev);
 };

 /*
  * Some of the buttons like volume up/down are auto repeat, while others
  * are not. To support both, we register two platform devices, and put
  * buttons into them based on whether the key should be auto repeat.
  */
 #define BUTTON_TYPES	2

 struct soc_button_data {
 	struct platform_device *children[BUTTON_TYPES];
 };

 /*
  * Get the Nth GPIO number from the ACPI object.
  */
 static int soc_button_lookup_gpio(struct device *dev, int acpi_index)
 {
 	struct gpio_desc *desc;
 	int gpio;

 	desc = gpiod_get_index(dev, NULL, acpi_index, GPIOD_ASIS);
 	if (IS_ERR(desc))
 		return PTR_ERR(desc);

 	gpio = desc_to_gpio(desc);

 	gpiod_put(desc);

 	return gpio;
 }

 static struct platform_device *
 soc_button_device_create(struct platform_device *pdev,
 			 const struct soc_button_info *button_info,
 			 bool autorepeat)
 {
 	const struct soc_button_info *info;
 	struct platform_device *pd;
 	struct gpio_keys_button *gpio_keys;
 	struct gpio_keys_platform_data *gpio_keys_pdata;
 	int n_buttons = 0;
 	int gpio;
 	int error;

 	for (info = button_info; info->name; info++)
 		if (info->autorepeat == autorepeat)
 			n_buttons++;

 	gpio_keys_pdata = devm_kzalloc(&pdev->dev,
 				       sizeof(*gpio_keys_pdata) +
 					sizeof(*gpio_keys) * n_buttons,
 				       GFP_KERNEL);
 	if (!gpio_keys_pdata)
 		return ERR_PTR(-ENOMEM);

 	gpio_keys = (void *)(gpio_keys_pdata + 1);
 	n_buttons = 0;

 	for (info = button_info; info->name; info++) {
 		if (info->autorepeat != autorepeat)
 			continue;

 		gpio = soc_button_lookup_gpio(&pdev->dev, info->acpi_index);
 		if (!gpio_is_valid(gpio)) {
 			/*
 			 * Skip GPIO if not present. Note we deliberately
 			 * ignore -EPROBE_DEFER errors here. On some devices
 			 * Intel is using so called virtual GPIOs which are not
 			 * GPIOs at all but some way for AML code to check some
 			 * random status bits without need a custom opregion.
 			 * In some cases the resources table we parse points to
 			 * such a virtual GPIO, since these are not real GPIOs
 			 * we do not have a driver for these so they will never
 			 * show up, therefore we ignore -EPROBE_DEFER.
 			 */
 			continue;
 		}

 		gpio_keys[n_buttons].type = info->event_type;
 		gpio_keys[n_buttons].code = info->event_code;
 		gpio_keys[n_buttons].gpio = gpio;
 		gpio_keys[n_buttons].active_low = 1;
 		gpio_keys[n_buttons].desc = info->name;
 		gpio_keys[n_buttons].wakeup = info->wakeup;
 		/* These devices often use cheap buttons, use 50 ms debounce */
 		gpio_keys[n_buttons].debounce_interval = 50;
 		n_buttons++;
 	}

 	if (n_buttons == 0) {
 		error = -ENODEV;
 		goto err_free_mem;
 	}

 	gpio_keys_pdata->buttons = gpio_keys;
 	gpio_keys_pdata->nbuttons = n_buttons;
 	gpio_keys_pdata->rep = autorepeat;

 	pd = platform_device_register_resndata(&pdev->dev, "gpio-keys",
 					       PLATFORM_DEVID_AUTO, NULL, 0,
 					       gpio_keys_pdata,
 					       sizeof(*gpio_keys_pdata));
 	error = PTR_ERR_OR_ZERO(pd);
 	if (error) {
 		dev_err(&pdev->dev,
 			"failed registering gpio-keys: %d\n", error);
 		goto err_free_mem;
 	}

 	return pd;

 err_free_mem:
 	devm_kfree(&pdev->dev, gpio_keys_pdata);
 	return ERR_PTR(error);
 }

 static int soc_button_get_acpi_object_int(const union acpi_object *obj)
 {
 	if (obj->type != ACPI_TYPE_INTEGER)
 		return -1;

 	return obj->integer.value;
 }

 /* Parse a single ACPI0011 _DSD button descriptor */
 static int soc_button_parse_btn_desc(struct device *dev,
 				     const union acpi_object *desc,
 				     int collection_uid,
 				     struct soc_button_info *info)
 {
 	int upage, usage;

 	if (desc->type != ACPI_TYPE_PACKAGE ||
 	    desc->package.count != 5 ||
 	    /* First byte should be 1 (control) */
 	    soc_button_get_acpi_object_int(&desc->package.elements[0]) != 1 ||
 	    /* Third byte should be collection uid */
 	    soc_button_get_acpi_object_int(&desc->package.elements[2]) !=
 							    collection_uid) {
 		dev_err(dev, "Invalid ACPI Button Descriptor\n");
 		return -ENODEV;
 	}

 	info->event_type = EV_KEY;
 	info->acpi_index =
 		soc_button_get_acpi_object_int(&desc->package.elements[1]);
 	upage = soc_button_get_acpi_object_int(&desc->package.elements[3]);
 	usage = soc_button_get_acpi_object_int(&desc->package.elements[4]);

 	/*
 	 * The UUID: fa6bd625-9ce8-470d-a2c7-b3ca36c4282e descriptors use HID
 	 * usage page and usage codes, but otherwise the device is not HID
 	 * compliant: it uses one irq per button instead of generating HID
 	 * input reports and some buttons should generate wakeups where as
 	 * others should not, so we cannot use the HID subsystem.
 	 *
 	 * Luckily all devices only use a few usage page + usage combinations,
 	 * so we can simply check for the known combinations here.
 	 */
 	if (upage == 0x01 && usage == 0x81) {
 		info->name = "power";
 		info->event_code = KEY_POWER;
 		info->wakeup = true;
 	} else if (upage == 0x01 && usage == 0xca) {
 		info->name = "rotation lock switch";
 		info->event_type = EV_SW;
 		info->event_code = SW_ROTATE_LOCK;
 	} else if (upage == 0x07 && usage == 0xe3) {
 		info->name = "home";
 		info->event_code = KEY_LEFTMETA;
 		info->wakeup = true;
 	} else if (upage == 0x0c && usage == 0xe9) {
 		info->name = "volume_up";
 		info->event_code = KEY_VOLUMEUP;
 		info->autorepeat = true;
 	} else if (upage == 0x0c && usage == 0xea) {
 		info->name = "volume_down";
 		info->event_code = KEY_VOLUMEDOWN;
 		info->autorepeat = true;
 	} else {
 		dev_warn(dev, "Unknown button index %d upage %02x usage %02x, ignoring\n",
 			 info->acpi_index, upage, usage);
 		info->name = "unknown";
 		info->event_code = KEY_RESERVED;
 	}

 	return 0;
 }

 /* ACPI0011 _DSD btns descriptors UUID: fa6bd625-9ce8-470d-a2c7-b3ca36c4282e */
 static const u8 btns_desc_uuid[16] = {
 	0x25, 0xd6, 0x6b, 0xfa, 0xe8, 0x9c, 0x0d, 0x47,
 	0xa2, 0xc7, 0xb3, 0xca, 0x36, 0xc4, 0x28, 0x2e
 };

 /* Parse ACPI0011 _DSD button descriptors */
 static struct soc_button_info *soc_button_get_button_info(struct device *dev)
 {
 	struct acpi_buffer buf = { ACPI_ALLOCATE_BUFFER };
 	const union acpi_object *desc, *el0, *uuid, *btns_desc = NULL;
 	struct soc_button_info *button_info;
 	acpi_status status;
 	int i, btn, collection_uid = -1;

 	status = acpi_evaluate_object_typed(ACPI_HANDLE(dev), "_DSD", NULL,
 					    &buf, ACPI_TYPE_PACKAGE);
 	if (ACPI_FAILURE(status)) {
 		dev_err(dev, "ACPI _DSD object not found\n");
 		return ERR_PTR(-ENODEV);
 	}

 	/* Look for the Button Descriptors UUID */
 	desc = buf.pointer;
 	for (i = 0; (i + 1) < desc->package.count; i += 2) {
 		uuid = &desc->package.elements[i];

 		if (uuid->type != ACPI_TYPE_BUFFER ||
 		    uuid->buffer.length != 16 ||
 		    desc->package.elements[i + 1].type != ACPI_TYPE_PACKAGE) {
 			break;
 		}

 		if (memcmp(uuid->buffer.pointer, btns_desc_uuid, 16) == 0) {
 			btns_desc = &desc->package.elements[i + 1];
 			break;
 		}
 	}

 	if (!btns_desc) {
 		dev_err(dev, "ACPI Button Descriptors not found\n");
 		button_info = ERR_PTR(-ENODEV);
 		goto out;
 	}

 	/* The first package describes the collection */
 	el0 = &btns_desc->package.elements[0];
 	if (el0->type == ACPI_TYPE_PACKAGE &&
 	    el0->package.count == 5 &&
 	    /* First byte should be 0 (collection) */
 	    soc_button_get_acpi_object_int(&el0->package.elements[0]) == 0 &&
 	    /* Third byte should be 0 (top level collection) */
 	    soc_button_get_acpi_object_int(&el0->package.elements[2]) == 0) {
 		collection_uid = soc_button_get_acpi_object_int(
 						&el0->package.elements[1]);
 	}
 	if (collection_uid == -1) {
 		dev_err(dev, "Invalid Button Collection Descriptor\n");
 		button_info = ERR_PTR(-ENODEV);
 		goto out;
 	}

 	/* There are package.count - 1 buttons + 1 terminating empty entry */
 	button_info = devm_kcalloc(dev, btns_desc->package.count,
 				   sizeof(*button_info), GFP_KERNEL);
 	if (!button_info) {
 		button_info = ERR_PTR(-ENOMEM);
 		goto out;
 	}

 	/* Parse the button descriptors */
 	for (i = 1, btn = 0; i < btns_desc->package.count; i++, btn++) {
 		if (soc_button_parse_btn_desc(dev,
 					      &btns_desc->package.elements[i],
 					      collection_uid,
 					      &button_info[btn])) {
 			button_info = ERR_PTR(-ENODEV);
 			goto out;
 		}
 	}

 out:
 	kfree(buf.pointer);
 	return button_info;
 }

 static int soc_button_remove(struct platform_device *pdev)
 {
 	struct soc_button_data *priv = platform_get_drvdata(pdev);

 	int i;

 	for (i = 0; i < BUTTON_TYPES; i++)
 		if (priv->children[i])
 			platform_device_unregister(priv->children[i]);

 	return 0;
 }

 static int soc_button_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	const struct soc_device_data *device_data;
 	const struct soc_button_info *button_info;
 	struct soc_button_data *priv;
 	struct platform_device *pd;
 	int i;
 	int error;

 	device_data = acpi_device_get_match_data(dev);
 	if (device_data && device_data->check) {
 		error = device_data->check(dev);
 		if (error)
 			return error;
 	}

 	if (device_data && device_data->button_info) {
 		button_info = device_data->button_info;
 	} else {
 		button_info = soc_button_get_button_info(dev);
 		if (IS_ERR(button_info))
 			return PTR_ERR(button_info);
 	}

 	error = gpiod_count(dev, NULL);
 	if (error < 0) {
 		dev_dbg(dev, "no GPIO attached, ignoring...\n");
 		return -ENODEV;
 	}

 	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;

 	platform_set_drvdata(pdev, priv);

 	for (i = 0; i < BUTTON_TYPES; i++) {
 		pd = soc_button_device_create(pdev, button_info, i == 0);
 		if (IS_ERR(pd)) {
 			error = PTR_ERR(pd);
 			if (error != -ENODEV) {
 				soc_button_remove(pdev);
 				return error;
 			}
 			continue;
 		}

 		priv->children[i] = pd;
 	}

 	if (!priv->children[0] && !priv->children[1])
 		return -ENODEV;

 	if (!device_data || !device_data->button_info)
 		devm_kfree(dev, button_info);

 	return 0;
 }

 /*
  * Definition of buttons on the tablet. The ACPI index of each button
  * is defined in section 2.8.7.2 of "Windows ACPI Design Guide for SoC
  * Platforms"
  */
 static const struct soc_button_info soc_button_PNP0C40[] = {
 	{ "power", 0, EV_KEY, KEY_POWER, false, true },
 	{ "home", 1, EV_KEY, KEY_LEFTMETA, false, true },
 	{ "volume_up", 2, EV_KEY, KEY_VOLUMEUP, true, false },
 	{ "volume_down", 3, EV_KEY, KEY_VOLUMEDOWN, true, false },
 	{ "rotation_lock", 4, EV_KEY, KEY_ROTATE_LOCK_TOGGLE, false, false },
 	{ }
 };

 static const struct soc_device_data soc_device_PNP0C40 = {
 	.button_info = soc_button_PNP0C40,
 };

 /*
  * Special device check for Surface Book 2 and Surface Pro (2017).
  * Both, the Surface Pro 4 (surfacepro3_button.c) and the above mentioned
  * devices use MSHW0040 for power and volume buttons, however the way they
  * have to be addressed differs. Make sure that we only load this drivers
  * for the correct devices by checking the OEM Platform Revision provided by
  * the _DSM method.
  */
 #define MSHW0040_DSM_REVISION		0x01
 #define MSHW0040_DSM_GET_OMPR		0x02	// get OEM Platform Revision
 static const guid_t MSHW0040_DSM_UUID =
 	GUID_INIT(0x6fd05c69, 0xcde3, 0x49f4, 0x95, 0xed, 0xab, 0x16, 0x65,
 		  0x49, 0x80, 0x35);

 static int soc_device_check_MSHW0040(struct device *dev)
 {
 	acpi_handle handle = ACPI_HANDLE(dev);
 	union acpi_object *result;
 	u64 oem_platform_rev = 0;	// valid revisions are nonzero

 	// get OEM platform revision
 	result = acpi_evaluate_dsm_typed(handle, &MSHW0040_DSM_UUID,
 					 MSHW0040_DSM_REVISION,
 					 MSHW0040_DSM_GET_OMPR, NULL,
 					 ACPI_TYPE_INTEGER);

 	if (result) {
 		oem_platform_rev = result->integer.value;
 		ACPI_FREE(result);
 	}

 	/*
 	 * If the revision is zero here, the _DSM evaluation has failed. This
 	 * indicates that we have a Pro 4 or Book 1 and this driver should not
 	 * be used.
 	 */
 	if (oem_platform_rev == 0)
 		return -ENODEV;

 	dev_dbg(dev, "OEM Platform Revision %llu\n", oem_platform_rev);

 	return 0;
 }

 /*
  * Button infos for Microsoft Surface Book 2 and Surface Pro (2017).
  * Obtained from DSDT/testing.
  */
 static const struct soc_button_info soc_button_MSHW0040[] = {
 	{ "power", 0, EV_KEY, KEY_POWER, false, true },
 	{ "volume_up", 2, EV_KEY, KEY_VOLUMEUP, true, false },
 	{ "volume_down", 4, EV_KEY, KEY_VOLUMEDOWN, true, false },
 	{ }
 };

 static const struct soc_device_data soc_device_MSHW0040 = {
 	.button_info = soc_button_MSHW0040,
 	.check = soc_device_check_MSHW0040,
 };

 static const struct acpi_device_id soc_button_acpi_match[] = {
 	{ "PNP0C40", (unsigned long)&soc_device_PNP0C40 },
 	{ "ACPI0011", 0 },

 	/* Microsoft Surface Devices (5th and 6th generation) */
 	{ "MSHW0040", (unsigned long)&soc_device_MSHW0040 },

 	{ }
 };

 MODULE_DEVICE_TABLE(acpi, soc_button_acpi_match);

 static struct platform_driver soc_button_driver = {
 	.probe          = soc_button_probe,
 	.remove		= soc_button_remove,
 	.driver		= {
 		.name = KBUILD_MODNAME,
 		.acpi_match_table = ACPI_PTR(soc_button_acpi_match),
 	},
 };
 module_platform_driver(soc_button_driver);

 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Supports for the button array on SoC tablets originally running
	* Windows 8.
	*
	* (C) Copyright 2014 Intel Corporation
	*/

	#include <linux/module.h>
	#include <linux/input.h>
	#include <linux/init.h>
	#include <linux/kernel.h>
	#include <linux/acpi.h>
	#include <linux/gpio/consumer.h>
	#include <linux/gpio_keys.h>
	#include <linux/gpio.h>
	#include <linux/platform_device.h>

	struct soc_button_info {
	const char *name;
	int acpi_index;
	unsigned int event_type;
	unsigned int event_code;
	bool autorepeat;
	bool wakeup;
	};

	struct soc_device_data {
	const struct soc_button_info *button_info;
	int (check)(struct device dev);
	};

	/*
	* Some of the buttons like volume up/down are auto repeat, while others
	* are not. To support both, we register two platform devices, and put
	* buttons into them based on whether the key should be auto repeat.
	*/
	#define BUTTON_TYPES 2

	struct soc_button_data {
	struct platform_device *children[BUTTON_TYPES];
	};

	/*
	* Get the Nth GPIO number from the ACPI object.
	*/
	static int soc_button_lookup_gpio(struct device *dev, int acpi_index)
	{
	struct gpio_desc *desc;
	int gpio;

	desc = gpiod_get_index(dev, NULL, acpi_index, GPIOD_ASIS);
	if (IS_ERR(desc))
	return PTR_ERR(desc);

	gpio = desc_to_gpio(desc);

	gpiod_put(desc);

	return gpio;
	}

	static struct platform_device *
	soc_button_device_create(struct platform_device *pdev,
	const struct soc_button_info *button_info,
	bool autorepeat)
	{
	const struct soc_button_info *info;
	struct platform_device *pd;
	struct gpio_keys_button *gpio_keys;
	struct gpio_keys_platform_data *gpio_keys_pdata;
	int n_buttons = 0;
	int gpio;
	int error;

	for (info = button_info; info->name; info++)
	if (info->autorepeat == autorepeat)
	n_buttons++;

	gpio_keys_pdata = devm_kzalloc(&pdev->dev,
	sizeof(*gpio_keys_pdata) +
	sizeof(gpio_keys) n_buttons,
	GFP_KERNEL);
	if (!gpio_keys_pdata)
	return ERR_PTR(-ENOMEM);

	gpio_keys = (void *)(gpio_keys_pdata + 1);
	n_buttons = 0;

	for (info = button_info; info->name; info++) {
	if (info->autorepeat != autorepeat)
	continue;

	gpio = soc_button_lookup_gpio(&pdev->dev, info->acpi_index);
	if (!gpio_is_valid(gpio)) {
	/*
	* Skip GPIO if not present. Note we deliberately
	* ignore -EPROBE_DEFER errors here. On some devices
	* Intel is using so called virtual GPIOs which are not
	* GPIOs at all but some way for AML code to check some
	* random status bits without need a custom opregion.
	* In some cases the resources table we parse points to
	* such a virtual GPIO, since these are not real GPIOs
	* we do not have a driver for these so they will never
	* show up, therefore we ignore -EPROBE_DEFER.
	*/
	continue;
	}

	gpio_keys[n_buttons].type = info->event_type;
	gpio_keys[n_buttons].code = info->event_code;
	gpio_keys[n_buttons].gpio = gpio;
	gpio_keys[n_buttons].active_low = 1;
	gpio_keys[n_buttons].desc = info->name;
	gpio_keys[n_buttons].wakeup = info->wakeup;
	/* These devices often use cheap buttons, use 50 ms debounce */
	gpio_keys[n_buttons].debounce_interval = 50;
	n_buttons++;
	}

	if (n_buttons == 0) {
	error = -ENODEV;
	goto err_free_mem;
	}

	gpio_keys_pdata->buttons = gpio_keys;
	gpio_keys_pdata->nbuttons = n_buttons;
	gpio_keys_pdata->rep = autorepeat;

	pd = platform_device_register_resndata(&pdev->dev, "gpio-keys",
	PLATFORM_DEVID_AUTO, NULL, 0,
	gpio_keys_pdata,
	sizeof(*gpio_keys_pdata));
	error = PTR_ERR_OR_ZERO(pd);
	if (error) {
	dev_err(&pdev->dev,
	"failed registering gpio-keys: %d\n", error);
	goto err_free_mem;
	}

	return pd;

	err_free_mem:
	devm_kfree(&pdev->dev, gpio_keys_pdata);
	return ERR_PTR(error);
	}

	static int soc_button_get_acpi_object_int(const union acpi_object *obj)
	{
	if (obj->type != ACPI_TYPE_INTEGER)
	return -1;

	return obj->integer.value;
	}

	/* Parse a single ACPI0011 _DSD button descriptor */
	static int soc_button_parse_btn_desc(struct device *dev,
	const union acpi_object *desc,
	int collection_uid,
	struct soc_button_info *info)
	{
	int upage, usage;

	if (desc->type != ACPI_TYPE_PACKAGE \|\|
	desc->package.count != 5 \|\|
	/* First byte should be 1 (control) */
	soc_button_get_acpi_object_int(&desc->package.elements[0]) != 1 \|\|
	/* Third byte should be collection uid */
	soc_button_get_acpi_object_int(&desc->package.elements[2]) !=
	collection_uid) {
	dev_err(dev, "Invalid ACPI Button Descriptor\n");
	return -ENODEV;
	}

	info->event_type = EV_KEY;
	info->acpi_index =
	soc_button_get_acpi_object_int(&desc->package.elements[1]);
	upage = soc_button_get_acpi_object_int(&desc->package.elements[3]);
	usage = soc_button_get_acpi_object_int(&desc->package.elements[4]);

	/*
	* The UUID: fa6bd625-9ce8-470d-a2c7-b3ca36c4282e descriptors use HID
	* usage page and usage codes, but otherwise the device is not HID
	* compliant: it uses one irq per button instead of generating HID
	* input reports and some buttons should generate wakeups where as
	* others should not, so we cannot use the HID subsystem.
	*
	* Luckily all devices only use a few usage page + usage combinations,
	* so we can simply check for the known combinations here.
	*/
	if (upage == 0x01 && usage == 0x81) {
	info->name = "power";
	info->event_code = KEY_POWER;
	info->wakeup = true;
	} else if (upage == 0x01 && usage == 0xca) {
	info->name = "rotation lock switch";
	info->event_type = EV_SW;
	info->event_code = SW_ROTATE_LOCK;
	} else if (upage == 0x07 && usage == 0xe3) {
	info->name = "home";
	info->event_code = KEY_LEFTMETA;
	info->wakeup = true;
	} else if (upage == 0x0c && usage == 0xe9) {
	info->name = "volume_up";
	info->event_code = KEY_VOLUMEUP;
	info->autorepeat = true;
	} else if (upage == 0x0c && usage == 0xea) {
	info->name = "volume_down";
	info->event_code = KEY_VOLUMEDOWN;
	info->autorepeat = true;
	} else {
	dev_warn(dev, "Unknown button index %d upage %02x usage %02x, ignoring\n",
	info->acpi_index, upage, usage);
	info->name = "unknown";
	info->event_code = KEY_RESERVED;
	}

	return 0;
	}

	/* ACPI0011 _DSD btns descriptors UUID: fa6bd625-9ce8-470d-a2c7-b3ca36c4282e */
	static const u8 btns_desc_uuid[16] = {
	0x25, 0xd6, 0x6b, 0xfa, 0xe8, 0x9c, 0x0d, 0x47,
	0xa2, 0xc7, 0xb3, 0xca, 0x36, 0xc4, 0x28, 0x2e
	};

	/* Parse ACPI0011 _DSD button descriptors */
	static struct soc_button_info soc_button_get_button_info(struct device dev)
	{
	struct acpi_buffer buf = { ACPI_ALLOCATE_BUFFER };
	const union acpi_object desc, el0, uuid, btns_desc = NULL;
	struct soc_button_info *button_info;
	acpi_status status;
	int i, btn, collection_uid = -1;

	status = acpi_evaluate_object_typed(ACPI_HANDLE(dev), "_DSD", NULL,
	&buf, ACPI_TYPE_PACKAGE);
	if (ACPI_FAILURE(status)) {
	dev_err(dev, "ACPI _DSD object not found\n");
	return ERR_PTR(-ENODEV);
	}

	/* Look for the Button Descriptors UUID */
	desc = buf.pointer;
	for (i = 0; (i + 1) < desc->package.count; i += 2) {
	uuid = &desc->package.elements[i];

	if (uuid->type != ACPI_TYPE_BUFFER \|\|
	uuid->buffer.length != 16 \|\|
	desc->package.elements[i + 1].type != ACPI_TYPE_PACKAGE) {
	break;
	}

	if (memcmp(uuid->buffer.pointer, btns_desc_uuid, 16) == 0) {
	btns_desc = &desc->package.elements[i + 1];
	break;
	}
	}

	if (!btns_desc) {
	dev_err(dev, "ACPI Button Descriptors not found\n");
	button_info = ERR_PTR(-ENODEV);
	goto out;
	}

	/* The first package describes the collection */
	el0 = &btns_desc->package.elements[0];
	if (el0->type == ACPI_TYPE_PACKAGE &&
	el0->package.count == 5 &&
	/* First byte should be 0 (collection) */
	soc_button_get_acpi_object_int(&el0->package.elements[0]) == 0 &&
	/* Third byte should be 0 (top level collection) */
	soc_button_get_acpi_object_int(&el0->package.elements[2]) == 0) {
	collection_uid = soc_button_get_acpi_object_int(
	&el0->package.elements[1]);
	}
	if (collection_uid == -1) {
	dev_err(dev, "Invalid Button Collection Descriptor\n");
	button_info = ERR_PTR(-ENODEV);
	goto out;
	}

	/* There are package.count - 1 buttons + 1 terminating empty entry */
	button_info = devm_kcalloc(dev, btns_desc->package.count,
	sizeof(*button_info), GFP_KERNEL);
	if (!button_info) {
	button_info = ERR_PTR(-ENOMEM);
	goto out;
	}

	/* Parse the button descriptors */
	for (i = 1, btn = 0; i < btns_desc->package.count; i++, btn++) {
	if (soc_button_parse_btn_desc(dev,
	&btns_desc->package.elements[i],
	collection_uid,
	&button_info[btn])) {
	button_info = ERR_PTR(-ENODEV);
	goto out;
	}
	}

	out:
	kfree(buf.pointer);
	return button_info;
	}

	static int soc_button_remove(struct platform_device *pdev)
	{
	struct soc_button_data *priv = platform_get_drvdata(pdev);

	int i;

	for (i = 0; i < BUTTON_TYPES; i++)
	if (priv->children[i])
	platform_device_unregister(priv->children[i]);

	return 0;
	}

	static int soc_button_probe(struct platform_device *pdev)
	{
	struct device *dev = &pdev->dev;
	const struct soc_device_data *device_data;
	const struct soc_button_info *button_info;
	struct soc_button_data *priv;
	struct platform_device *pd;
	int i;
	int error;

	device_data = acpi_device_get_match_data(dev);
	if (device_data && device_data->check) {
	error = device_data->check(dev);
	if (error)
	return error;
	}

	if (device_data && device_data->button_info) {
	button_info = device_data->button_info;
	} else {
	button_info = soc_button_get_button_info(dev);
	if (IS_ERR(button_info))
	return PTR_ERR(button_info);
	}

	error = gpiod_count(dev, NULL);
	if (error < 0) {
	dev_dbg(dev, "no GPIO attached, ignoring...\n");
	return -ENODEV;
	}

	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
	if (!priv)
	return -ENOMEM;

	platform_set_drvdata(pdev, priv);

	for (i = 0; i < BUTTON_TYPES; i++) {
	pd = soc_button_device_create(pdev, button_info, i == 0);
	if (IS_ERR(pd)) {
	error = PTR_ERR(pd);
	if (error != -ENODEV) {
	soc_button_remove(pdev);
	return error;
	}
	continue;
	}

	priv->children[i] = pd;
	}

	if (!priv->children[0] && !priv->children[1])
	return -ENODEV;

	if (!device_data \|\| !device_data->button_info)
	devm_kfree(dev, button_info);

	return 0;
	}

	/*
	* Definition of buttons on the tablet. The ACPI index of each button
	* is defined in section 2.8.7.2 of "Windows ACPI Design Guide for SoC
	* Platforms"
	*/
	static const struct soc_button_info soc_button_PNP0C40[] = {
	{ "power", 0, EV_KEY, KEY_POWER, false, true },
	{ "home", 1, EV_KEY, KEY_LEFTMETA, false, true },
	{ "volume_up", 2, EV_KEY, KEY_VOLUMEUP, true, false },
	{ "volume_down", 3, EV_KEY, KEY_VOLUMEDOWN, true, false },
	{ "rotation_lock", 4, EV_KEY, KEY_ROTATE_LOCK_TOGGLE, false, false },
	{ }
	};

	static const struct soc_device_data soc_device_PNP0C40 = {
	.button_info = soc_button_PNP0C40,
	};

	/*
	* Special device check for Surface Book 2 and Surface Pro (2017).
	* Both, the Surface Pro 4 (surfacepro3_button.c) and the above mentioned
	* devices use MSHW0040 for power and volume buttons, however the way they
	* have to be addressed differs. Make sure that we only load this drivers
	* for the correct devices by checking the OEM Platform Revision provided by
	* the _DSM method.
	*/
	#define MSHW0040_DSM_REVISION 0x01
	#define MSHW0040_DSM_GET_OMPR 0x02 // get OEM Platform Revision
	static const guid_t MSHW0040_DSM_UUID =
	GUID_INIT(0x6fd05c69, 0xcde3, 0x49f4, 0x95, 0xed, 0xab, 0x16, 0x65,
	0x49, 0x80, 0x35);

	static int soc_device_check_MSHW0040(struct device *dev)
	{
	acpi_handle handle = ACPI_HANDLE(dev);
	union acpi_object *result;
	u64 oem_platform_rev = 0; // valid revisions are nonzero

	// get OEM platform revision
	result = acpi_evaluate_dsm_typed(handle, &MSHW0040_DSM_UUID,
	MSHW0040_DSM_REVISION,
	MSHW0040_DSM_GET_OMPR, NULL,
	ACPI_TYPE_INTEGER);

	if (result) {
	oem_platform_rev = result->integer.value;
	ACPI_FREE(result);
	}

	/*
	* If the revision is zero here, the _DSM evaluation has failed. This
	* indicates that we have a Pro 4 or Book 1 and this driver should not
	* be used.
	*/
	if (oem_platform_rev == 0)
	return -ENODEV;

	dev_dbg(dev, "OEM Platform Revision %llu\n", oem_platform_rev);

	return 0;
	}

	/*
	* Button infos for Microsoft Surface Book 2 and Surface Pro (2017).
	* Obtained from DSDT/testing.
	*/
	static const struct soc_button_info soc_button_MSHW0040[] = {
	{ "power", 0, EV_KEY, KEY_POWER, false, true },
	{ "volume_up", 2, EV_KEY, KEY_VOLUMEUP, true, false },
	{ "volume_down", 4, EV_KEY, KEY_VOLUMEDOWN, true, false },
	{ }
	};

	static const struct soc_device_data soc_device_MSHW0040 = {
	.button_info = soc_button_MSHW0040,
	.check = soc_device_check_MSHW0040,
	};

	static const struct acpi_device_id soc_button_acpi_match[] = {
	{ "PNP0C40", (unsigned long)&soc_device_PNP0C40 },
	{ "ACPI0011", 0 },

	/* Microsoft Surface Devices (5th and 6th generation) */
	{ "MSHW0040", (unsigned long)&soc_device_MSHW0040 },

	{ }
	};

	MODULE_DEVICE_TABLE(acpi, soc_button_acpi_match);

	static struct platform_driver soc_button_driver = {
	.probe = soc_button_probe,
	.remove = soc_button_remove,
	.driver = {
	.name = KBUILD_MODNAME,
	.acpi_match_table = ACPI_PTR(soc_button_acpi_match),
	},
	};
	module_platform_driver(soc_button_driver);

	MODULE_LICENSE("GPL");