drivers/char/tpm/tpm-chip.c - third_party/kernel - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright (C) 2004 IBM Corporation
  * Copyright (C) 2014 Intel Corporation
  *
  * Authors:
  * Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
  * Leendert van Doorn <leendert@watson.ibm.com>
  * Dave Safford <safford@watson.ibm.com>
  * Reiner Sailer <sailer@watson.ibm.com>
  * Kylene Hall <kjhall@us.ibm.com>
  *
  * Maintained by: <tpmdd-devel@lists.sourceforge.net>
  *
  * TPM chip management routines.
  */

 #include <linux/poll.h>
 #include <linux/slab.h>
 #include <linux/mutex.h>
 #include <linux/spinlock.h>
 #include <linux/freezer.h>
 #include <linux/major.h>
 #include <linux/tpm_eventlog.h>
 #include <linux/hw_random.h>
 #include "tpm.h"

 DEFINE_IDR(dev_nums_idr);
 static DEFINE_MUTEX(idr_lock);

 struct class *tpm_class;
 struct class *tpmrm_class;
 dev_t tpm_devt;

 static int tpm_request_locality(struct tpm_chip *chip)
 {
 	int rc;

 	if (!chip->ops->request_locality)
 		return 0;

 	rc = chip->ops->request_locality(chip, 0);
 	if (rc < 0)
 		return rc;

 	chip->locality = rc;
 	return 0;
 }

 static void tpm_relinquish_locality(struct tpm_chip *chip)
 {
 	int rc;

 	if (!chip->ops->relinquish_locality)
 		return;

 	rc = chip->ops->relinquish_locality(chip, chip->locality);
 	if (rc)
 		dev_err(&chip->dev, "%s: : error %d\n", __func__, rc);

 	chip->locality = -1;
 }

 static int tpm_cmd_ready(struct tpm_chip *chip)
 {
 	if (!chip->ops->cmd_ready)
 		return 0;

 	return chip->ops->cmd_ready(chip);
 }

 static int tpm_go_idle(struct tpm_chip *chip)
 {
 	if (!chip->ops->go_idle)
 		return 0;

 	return chip->ops->go_idle(chip);
 }

 static void tpm_clk_enable(struct tpm_chip *chip)
 {
 	if (chip->ops->clk_enable)
 		chip->ops->clk_enable(chip, true);
 }

 static void tpm_clk_disable(struct tpm_chip *chip)
 {
 	if (chip->ops->clk_enable)
 		chip->ops->clk_enable(chip, false);
 }

 /**
  * tpm_chip_start() - power on the TPM
  * @chip:	a TPM chip to use
  *
  * Return:
  * * The response length	- OK
  * * -errno			- A system error
  */
 int tpm_chip_start(struct tpm_chip *chip)
 {
 	int ret;

 	tpm_clk_enable(chip);

 	if (chip->locality == -1) {
 		ret = tpm_request_locality(chip);
 		if (ret) {
 			tpm_clk_disable(chip);
 			return ret;
 		}
 	}

 	ret = tpm_cmd_ready(chip);
 	if (ret) {
 		tpm_relinquish_locality(chip);
 		tpm_clk_disable(chip);
 		return ret;
 	}

 	return 0;
 }
 EXPORT_SYMBOL_GPL(tpm_chip_start);

 /**
  * tpm_chip_stop() - power off the TPM
  * @chip:	a TPM chip to use
  *
  * Return:
  * * The response length	- OK
  * * -errno			- A system error
  */
 void tpm_chip_stop(struct tpm_chip *chip)
 {
 	tpm_go_idle(chip);
 	tpm_relinquish_locality(chip);
 	tpm_clk_disable(chip);
 }
 EXPORT_SYMBOL_GPL(tpm_chip_stop);

 /**
  * tpm_try_get_ops() - Get a ref to the tpm_chip
  * @chip: Chip to ref
  *
  * The caller must already have some kind of locking to ensure that chip is
  * valid. This function will lock the chip so that the ops member can be
  * accessed safely. The locking prevents tpm_chip_unregister from
  * completing, so it should not be held for long periods.
  *
  * Returns -ERRNO if the chip could not be got.
  */
 int tpm_try_get_ops(struct tpm_chip *chip)
 {
 	int rc = -EIO;

 	get_device(&chip->dev);

 	down_read(&chip->ops_sem);
 	if (!chip->ops)
 		goto out_ops;

 	mutex_lock(&chip->tpm_mutex);
 	rc = tpm_chip_start(chip);
 	if (rc)
 		goto out_lock;

 	return 0;
 out_lock:
 	mutex_unlock(&chip->tpm_mutex);
 out_ops:
 	up_read(&chip->ops_sem);
 	put_device(&chip->dev);
 	return rc;
 }
 EXPORT_SYMBOL_GPL(tpm_try_get_ops);

 /**
  * tpm_put_ops() - Release a ref to the tpm_chip
  * @chip: Chip to put
  *
  * This is the opposite pair to tpm_try_get_ops(). After this returns chip may
  * be kfree'd.
  */
 void tpm_put_ops(struct tpm_chip *chip)
 {
 	tpm_chip_stop(chip);
 	mutex_unlock(&chip->tpm_mutex);
 	up_read(&chip->ops_sem);
 	put_device(&chip->dev);
 }
 EXPORT_SYMBOL_GPL(tpm_put_ops);

 /**
  * tpm_default_chip() - find a TPM chip and get a reference to it
  */
 struct tpm_chip *tpm_default_chip(void)
 {
 	struct tpm_chip *chip, *res = NULL;
 	int chip_num = 0;
 	int chip_prev;

 	mutex_lock(&idr_lock);

 	do {
 		chip_prev = chip_num;
 		chip = idr_get_next(&dev_nums_idr, &chip_num);
 		if (chip) {
 			get_device(&chip->dev);
 			res = chip;
 			break;
 		}
 	} while (chip_prev != chip_num);

 	mutex_unlock(&idr_lock);

 	return res;
 }
 EXPORT_SYMBOL_GPL(tpm_default_chip);

 /**
  * tpm_find_get_ops() - find and reserve a TPM chip
  * @chip:	a &struct tpm_chip instance, %NULL for the default chip
  *
  * Finds a TPM chip and reserves its class device and operations. The chip must
  * be released with tpm_put_ops() after use.
  * This function is for internal use only. It supports existing TPM callers
  * by accepting NULL, but those callers should be converted to pass in a chip
  * directly.
  *
  * Return:
  * A reserved &struct tpm_chip instance.
  * %NULL if a chip is not found.
  * %NULL if the chip is not available.
  */
 struct tpm_chip *tpm_find_get_ops(struct tpm_chip *chip)
 {
 	int rc;

 	if (chip) {
 		if (!tpm_try_get_ops(chip))
 			return chip;
 		return NULL;
 	}

 	chip = tpm_default_chip();
 	if (!chip)
 		return NULL;
 	rc = tpm_try_get_ops(chip);
 	/* release additional reference we got from tpm_default_chip() */
 	put_device(&chip->dev);
 	if (rc)
 		return NULL;
 	return chip;
 }

 /**
  * tpm_dev_release() - free chip memory and the device number
  * @dev: the character device for the TPM chip
  *
  * This is used as the release function for the character device.
  */
 static void tpm_dev_release(struct device *dev)
 {
 	struct tpm_chip *chip = container_of(dev, struct tpm_chip, dev);

 	mutex_lock(&idr_lock);
 	idr_remove(&dev_nums_idr, chip->dev_num);
 	mutex_unlock(&idr_lock);

 	kfree(chip->log.bios_event_log);
 	kfree(chip->work_space.context_buf);
 	kfree(chip->work_space.session_buf);
 	kfree(chip->allocated_banks);
 	kfree(chip);
 }

 /**
  * tpm_class_shutdown() - prepare the TPM device for loss of power.
  * @dev: device to which the chip is associated.
  *
  * Issues a TPM2_Shutdown command prior to loss of power, as required by the
  * TPM 2.0 spec. Then, calls bus- and device- specific shutdown code.
  *
  * Return: always 0 (i.e. success)
  */
 static int tpm_class_shutdown(struct device *dev)
 {
 	struct tpm_chip *chip = container_of(dev, struct tpm_chip, dev);

 	down_write(&chip->ops_sem);
 	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
 		if (!tpm_chip_start(chip)) {
 			tpm2_shutdown(chip, TPM2_SU_CLEAR);
 			tpm_chip_stop(chip);
 		}
 	}
 	chip->ops = NULL;
 	up_write(&chip->ops_sem);

 	return 0;
 }

 /**
  * tpm_chip_alloc() - allocate a new struct tpm_chip instance
  * @pdev: device to which the chip is associated
  *        At this point pdev mst be initialized, but does not have to
  *        be registered
  * @ops: struct tpm_class_ops instance
  *
  * Allocates a new struct tpm_chip instance and assigns a free
  * device number for it. Must be paired with put_device(&chip->dev).
  */
 struct tpm_chip *tpm_chip_alloc(struct device *pdev,
 				const struct tpm_class_ops *ops)
 {
 	struct tpm_chip *chip;
 	int rc;

 	chip = kzalloc(sizeof(*chip), GFP_KERNEL);
 	if (chip == NULL)
 		return ERR_PTR(-ENOMEM);

 	mutex_init(&chip->tpm_mutex);
 	init_rwsem(&chip->ops_sem);

 	chip->ops = ops;

 	mutex_lock(&idr_lock);
 	rc = idr_alloc(&dev_nums_idr, NULL, 0, TPM_NUM_DEVICES, GFP_KERNEL);
 	mutex_unlock(&idr_lock);
 	if (rc < 0) {
 		dev_err(pdev, "No available tpm device numbers\n");
 		kfree(chip);
 		return ERR_PTR(rc);
 	}
 	chip->dev_num = rc;

 	device_initialize(&chip->dev);

 	chip->dev.class = tpm_class;
 	chip->dev.class->shutdown_pre = tpm_class_shutdown;
 	chip->dev.release = tpm_dev_release;
 	chip->dev.parent = pdev;
 	chip->dev.groups = chip->groups;

 	if (chip->dev_num == 0)
 		chip->dev.devt = MKDEV(MISC_MAJOR, TPM_MINOR);
 	else
 		chip->dev.devt = MKDEV(MAJOR(tpm_devt), chip->dev_num);

 	rc = dev_set_name(&chip->dev, "tpm%d", chip->dev_num);
 	if (rc)
 		goto out;

 	if (!pdev)
 		chip->flags |= TPM_CHIP_FLAG_VIRTUAL;

 	cdev_init(&chip->cdev, &tpm_fops);
 	chip->cdev.owner = THIS_MODULE;

 	rc = tpm2_init_space(&chip->work_space, TPM2_SPACE_BUFFER_SIZE);
 	if (rc) {
 		rc = -ENOMEM;
 		goto out;
 	}

 	chip->locality = -1;
 	return chip;

 out:
 	put_device(&chip->dev);
 	return ERR_PTR(rc);
 }
 EXPORT_SYMBOL_GPL(tpm_chip_alloc);

 /**
  * tpmm_chip_alloc() - allocate a new struct tpm_chip instance
  * @pdev: parent device to which the chip is associated
  * @ops: struct tpm_class_ops instance
  *
  * Same as tpm_chip_alloc except devm is used to do the put_device
  */
 struct tpm_chip *tpmm_chip_alloc(struct device *pdev,
 				 const struct tpm_class_ops *ops)
 {
 	struct tpm_chip *chip;
 	int rc;

 	chip = tpm_chip_alloc(pdev, ops);
 	if (IS_ERR(chip))
 		return chip;

 	rc = devm_add_action_or_reset(pdev,
 				      (void (*)(void *)) put_device,
 				      &chip->dev);
 	if (rc)
 		return ERR_PTR(rc);

 	dev_set_drvdata(pdev, chip);

 	return chip;
 }
 EXPORT_SYMBOL_GPL(tpmm_chip_alloc);

 static int tpm_add_char_device(struct tpm_chip *chip)
 {
 	int rc;

 	rc = cdev_device_add(&chip->cdev, &chip->dev);
 	if (rc) {
 		dev_err(&chip->dev,
 			"unable to cdev_device_add() %s, major %d, minor %d, err=%d\n",
 			dev_name(&chip->dev), MAJOR(chip->dev.devt),
 			MINOR(chip->dev.devt), rc);
 		return rc;
 	}

 	if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip)) {
 		rc = tpm_devs_add(chip);
 		if (rc)
 			goto err_del_cdev;
 	}

 	/* Make the chip available. */
 	mutex_lock(&idr_lock);
 	idr_replace(&dev_nums_idr, chip, chip->dev_num);
 	mutex_unlock(&idr_lock);

 	return 0;

 err_del_cdev:
 	cdev_device_del(&chip->cdev, &chip->dev);
 	return rc;
 }

 static void tpm_del_char_device(struct tpm_chip *chip)
 {
 	cdev_device_del(&chip->cdev, &chip->dev);

 	/* Make the chip unavailable. */
 	mutex_lock(&idr_lock);
 	idr_replace(&dev_nums_idr, NULL, chip->dev_num);
 	mutex_unlock(&idr_lock);

 	/* Make the driver uncallable. */
 	down_write(&chip->ops_sem);

 	/*
 	 * Check if chip->ops is still valid: In case that the controller
 	 * drivers shutdown handler unregisters the controller in its
 	 * shutdown handler we are called twice and chip->ops to NULL.
 	 */
 	if (chip->ops) {
 		if (chip->flags & TPM_CHIP_FLAG_TPM2) {
 			if (!tpm_chip_start(chip)) {
 				tpm2_shutdown(chip, TPM2_SU_CLEAR);
 				tpm_chip_stop(chip);
 			}
 		}
 		chip->ops = NULL;
 	}
 	up_write(&chip->ops_sem);
 }

 static void tpm_del_legacy_sysfs(struct tpm_chip *chip)
 {
 	struct attribute **i;

 	if (chip->flags & (TPM_CHIP_FLAG_TPM2 | TPM_CHIP_FLAG_VIRTUAL) ||
 	    tpm_is_firmware_upgrade(chip))
 		return;

 	sysfs_remove_link(&chip->dev.parent->kobj, "ppi");

 	for (i = chip->groups[0]->attrs; *i != NULL; ++i)
 		sysfs_remove_link(&chip->dev.parent->kobj, (*i)->name);
 }

 /* For compatibility with legacy sysfs paths we provide symlinks from the
  * parent dev directory to selected names within the tpm chip directory. Old
  * kernel versions created these files directly under the parent.
  */
 static int tpm_add_legacy_sysfs(struct tpm_chip *chip)
 {
 	struct attribute **i;
 	int rc;

 	if (chip->flags & (TPM_CHIP_FLAG_TPM2 | TPM_CHIP_FLAG_VIRTUAL) ||
 		tpm_is_firmware_upgrade(chip))
 		return 0;

 	rc = compat_only_sysfs_link_entry_to_kobj(
 		    &chip->dev.parent->kobj, &chip->dev.kobj, "ppi", NULL);
 	if (rc && rc != -ENOENT)
 		return rc;

 	/* All the names from tpm-sysfs */
 	for (i = chip->groups[0]->attrs; *i != NULL; ++i) {
 		rc = compat_only_sysfs_link_entry_to_kobj(
 		    &chip->dev.parent->kobj, &chip->dev.kobj, (*i)->name, NULL);
 		if (rc) {
 			tpm_del_legacy_sysfs(chip);
 			return rc;
 		}
 	}

 	return 0;
 }

 static int tpm_hwrng_read(struct hwrng *rng, void *data, size_t max, bool wait)
 {
 	struct tpm_chip *chip = container_of(rng, struct tpm_chip, hwrng);

 	return tpm_get_random(chip, data, max);
 }

 static int tpm_add_hwrng(struct tpm_chip *chip)
 {
 	if (!IS_ENABLED(CONFIG_HW_RANDOM_TPM) || tpm_is_firmware_upgrade(chip))
 		return 0;

 	snprintf(chip->hwrng_name, sizeof(chip->hwrng_name),
 		 "tpm-rng-%d", chip->dev_num);
 	chip->hwrng.name = chip->hwrng_name;
 	chip->hwrng.read = tpm_hwrng_read;
 	return hwrng_register(&chip->hwrng);
 }

 static int tpm_get_pcr_allocation(struct tpm_chip *chip)
 {
 	int rc;

 	if (tpm_is_firmware_upgrade(chip))
 		return 0;

 	rc = (chip->flags & TPM_CHIP_FLAG_TPM2) ?
 	     tpm2_get_pcr_allocation(chip) :
 	     tpm1_get_pcr_allocation(chip);

 	if (rc > 0)
 		return -ENODEV;

 	return rc;
 }

 /*
  * tpm_chip_register() - create a character device for the TPM chip
  * @chip: TPM chip to use.
  *
  * Creates a character device for the TPM chip and adds sysfs attributes for
  * the device. As the last step this function adds the chip to the list of TPM
  * chips available for in-kernel use.
  *
  * This function should be only called after the chip initialization is
  * complete.
  */
 int tpm_chip_register(struct tpm_chip *chip)
 {
 	int rc;

 	rc = tpm_chip_start(chip);
 	if (rc)
 		return rc;
 	rc = tpm_auto_startup(chip);
 	if (rc) {
 		tpm_chip_stop(chip);
 		return rc;
 	}

 	rc = tpm_get_pcr_allocation(chip);
 	tpm_chip_stop(chip);
 	if (rc)
 		return rc;

 	tpm_sysfs_add_device(chip);

 	tpm_bios_log_setup(chip);

 	tpm_add_ppi(chip);

 	rc = tpm_add_hwrng(chip);
 	if (rc)
 		goto out_ppi;

 	rc = tpm_add_char_device(chip);
 	if (rc)
 		goto out_hwrng;

 	rc = tpm_add_legacy_sysfs(chip);
 	if (rc) {
 		tpm_chip_unregister(chip);
 		return rc;
 	}

 	return 0;

 out_hwrng:
 	if (IS_ENABLED(CONFIG_HW_RANDOM_TPM) && !tpm_is_firmware_upgrade(chip))
 		hwrng_unregister(&chip->hwrng);
 out_ppi:
 	tpm_bios_log_teardown(chip);

 	return rc;
 }
 EXPORT_SYMBOL_GPL(tpm_chip_register);

 /*
  * tpm_chip_unregister() - release the TPM driver
  * @chip: TPM chip to use.
  *
  * Takes the chip first away from the list of available TPM chips and then
  * cleans up all the resources reserved by tpm_chip_register().
  *
  * Once this function returns the driver call backs in 'op's will not be
  * running and will no longer start.
  *
  * NOTE: This function should be only called before deinitializing chip
  * resources.
  */
 void tpm_chip_unregister(struct tpm_chip *chip)
 {
 	tpm_del_legacy_sysfs(chip);
 	if (IS_ENABLED(CONFIG_HW_RANDOM_TPM) && !tpm_is_firmware_upgrade(chip))
 		hwrng_unregister(&chip->hwrng);
 	tpm_bios_log_teardown(chip);
 	if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip))
 		tpm_devs_remove(chip);
 	tpm_del_char_device(chip);
 }
 EXPORT_SYMBOL_GPL(tpm_chip_unregister);
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Copyright (C) 2004 IBM Corporation
	* Copyright (C) 2014 Intel Corporation
	*
	* Authors:
	* Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
	* Leendert van Doorn <leendert@watson.ibm.com>
	* Dave Safford <safford@watson.ibm.com>
	* Reiner Sailer <sailer@watson.ibm.com>
	* Kylene Hall <kjhall@us.ibm.com>
	*
	* Maintained by: <tpmdd-devel@lists.sourceforge.net>
	*
	* TPM chip management routines.
	*/

	#include <linux/poll.h>
	#include <linux/slab.h>
	#include <linux/mutex.h>
	#include <linux/spinlock.h>
	#include <linux/freezer.h>
	#include <linux/major.h>
	#include <linux/tpm_eventlog.h>
	#include <linux/hw_random.h>
	#include "tpm.h"

	DEFINE_IDR(dev_nums_idr);
	static DEFINE_MUTEX(idr_lock);

	struct class *tpm_class;
	struct class *tpmrm_class;
	dev_t tpm_devt;

	static int tpm_request_locality(struct tpm_chip *chip)
	{
	int rc;

	if (!chip->ops->request_locality)
	return 0;

	rc = chip->ops->request_locality(chip, 0);
	if (rc < 0)
	return rc;

	chip->locality = rc;
	return 0;
	}

	static void tpm_relinquish_locality(struct tpm_chip *chip)
	{
	int rc;

	if (!chip->ops->relinquish_locality)
	return;

	rc = chip->ops->relinquish_locality(chip, chip->locality);
	if (rc)
	dev_err(&chip->dev, "%s: : error %d\n", __func__, rc);

	chip->locality = -1;
	}

	static int tpm_cmd_ready(struct tpm_chip *chip)
	{
	if (!chip->ops->cmd_ready)
	return 0;

	return chip->ops->cmd_ready(chip);
	}

	static int tpm_go_idle(struct tpm_chip *chip)
	{
	if (!chip->ops->go_idle)
	return 0;

	return chip->ops->go_idle(chip);
	}

	static void tpm_clk_enable(struct tpm_chip *chip)
	{
	if (chip->ops->clk_enable)
	chip->ops->clk_enable(chip, true);
	}

	static void tpm_clk_disable(struct tpm_chip *chip)
	{
	if (chip->ops->clk_enable)
	chip->ops->clk_enable(chip, false);
	}

	/**
	* tpm_chip_start() - power on the TPM
	* @chip: a TPM chip to use
	*
	* Return:
	* * The response length - OK
	* * -errno - A system error
	*/
	int tpm_chip_start(struct tpm_chip *chip)
	{
	int ret;

	tpm_clk_enable(chip);

	if (chip->locality == -1) {
	ret = tpm_request_locality(chip);
	if (ret) {
	tpm_clk_disable(chip);
	return ret;
	}
	}

	ret = tpm_cmd_ready(chip);
	if (ret) {
	tpm_relinquish_locality(chip);
	tpm_clk_disable(chip);
	return ret;
	}

	return 0;
	}
	EXPORT_SYMBOL_GPL(tpm_chip_start);

	/**
	* tpm_chip_stop() - power off the TPM
	* @chip: a TPM chip to use
	*
	* Return:
	* * The response length - OK
	* * -errno - A system error
	*/
	void tpm_chip_stop(struct tpm_chip *chip)
	{
	tpm_go_idle(chip);
	tpm_relinquish_locality(chip);
	tpm_clk_disable(chip);
	}
	EXPORT_SYMBOL_GPL(tpm_chip_stop);

	/**
	* tpm_try_get_ops() - Get a ref to the tpm_chip
	* @chip: Chip to ref
	*
	* The caller must already have some kind of locking to ensure that chip is
	* valid. This function will lock the chip so that the ops member can be
	* accessed safely. The locking prevents tpm_chip_unregister from
	* completing, so it should not be held for long periods.
	*
	* Returns -ERRNO if the chip could not be got.
	*/
	int tpm_try_get_ops(struct tpm_chip *chip)
	{
	int rc = -EIO;

	get_device(&chip->dev);

	down_read(&chip->ops_sem);
	if (!chip->ops)
	goto out_ops;

	mutex_lock(&chip->tpm_mutex);
	rc = tpm_chip_start(chip);
	if (rc)
	goto out_lock;

	return 0;
	out_lock:
	mutex_unlock(&chip->tpm_mutex);
	out_ops:
	up_read(&chip->ops_sem);
	put_device(&chip->dev);
	return rc;
	}
	EXPORT_SYMBOL_GPL(tpm_try_get_ops);

	/**
	* tpm_put_ops() - Release a ref to the tpm_chip
	* @chip: Chip to put
	*
	* This is the opposite pair to tpm_try_get_ops(). After this returns chip may
	* be kfree'd.
	*/
	void tpm_put_ops(struct tpm_chip *chip)
	{
	tpm_chip_stop(chip);
	mutex_unlock(&chip->tpm_mutex);
	up_read(&chip->ops_sem);
	put_device(&chip->dev);
	}
	EXPORT_SYMBOL_GPL(tpm_put_ops);

	/**
	* tpm_default_chip() - find a TPM chip and get a reference to it
	*/
	struct tpm_chip *tpm_default_chip(void)
	{
	struct tpm_chip chip, res = NULL;
	int chip_num = 0;
	int chip_prev;

	mutex_lock(&idr_lock);

	do {
	chip_prev = chip_num;
	chip = idr_get_next(&dev_nums_idr, &chip_num);
	if (chip) {
	get_device(&chip->dev);
	res = chip;
	break;
	}
	} while (chip_prev != chip_num);

	mutex_unlock(&idr_lock);

	return res;
	}
	EXPORT_SYMBOL_GPL(tpm_default_chip);

	/**
	* tpm_find_get_ops() - find and reserve a TPM chip
	* @chip: a &struct tpm_chip instance, %NULL for the default chip
	*
	* Finds a TPM chip and reserves its class device and operations. The chip must
	* be released with tpm_put_ops() after use.
	* This function is for internal use only. It supports existing TPM callers
	* by accepting NULL, but those callers should be converted to pass in a chip
	* directly.
	*
	* Return:
	* A reserved &struct tpm_chip instance.
	* %NULL if a chip is not found.
	* %NULL if the chip is not available.
	*/
	struct tpm_chip tpm_find_get_ops(struct tpm_chip chip)
	{
	int rc;

	if (chip) {
	if (!tpm_try_get_ops(chip))
	return chip;
	return NULL;
	}

	chip = tpm_default_chip();
	if (!chip)
	return NULL;
	rc = tpm_try_get_ops(chip);
	/* release additional reference we got from tpm_default_chip() */
	put_device(&chip->dev);
	if (rc)
	return NULL;
	return chip;
	}

	/**
	* tpm_dev_release() - free chip memory and the device number
	* @dev: the character device for the TPM chip
	*
	* This is used as the release function for the character device.
	*/
	static void tpm_dev_release(struct device *dev)
	{
	struct tpm_chip *chip = container_of(dev, struct tpm_chip, dev);

	mutex_lock(&idr_lock);
	idr_remove(&dev_nums_idr, chip->dev_num);
	mutex_unlock(&idr_lock);

	kfree(chip->log.bios_event_log);
	kfree(chip->work_space.context_buf);
	kfree(chip->work_space.session_buf);
	kfree(chip->allocated_banks);
	kfree(chip);
	}

	/**
	* tpm_class_shutdown() - prepare the TPM device for loss of power.
	* @dev: device to which the chip is associated.
	*
	* Issues a TPM2_Shutdown command prior to loss of power, as required by the
	* TPM 2.0 spec. Then, calls bus- and device- specific shutdown code.
	*
	* Return: always 0 (i.e. success)
	*/
	static int tpm_class_shutdown(struct device *dev)
	{
	struct tpm_chip *chip = container_of(dev, struct tpm_chip, dev);

	down_write(&chip->ops_sem);
	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
	if (!tpm_chip_start(chip)) {
	tpm2_shutdown(chip, TPM2_SU_CLEAR);
	tpm_chip_stop(chip);
	}
	}
	chip->ops = NULL;
	up_write(&chip->ops_sem);

	return 0;
	}

	/**
	* tpm_chip_alloc() - allocate a new struct tpm_chip instance
	* @pdev: device to which the chip is associated
	* At this point pdev mst be initialized, but does not have to
	* be registered
	* @ops: struct tpm_class_ops instance
	*
	* Allocates a new struct tpm_chip instance and assigns a free
	* device number for it. Must be paired with put_device(&chip->dev).
	*/
	struct tpm_chip tpm_chip_alloc(struct device pdev,
	const struct tpm_class_ops *ops)
	{
	struct tpm_chip *chip;
	int rc;

	chip = kzalloc(sizeof(*chip), GFP_KERNEL);
	if (chip == NULL)
	return ERR_PTR(-ENOMEM);

	mutex_init(&chip->tpm_mutex);
	init_rwsem(&chip->ops_sem);

	chip->ops = ops;

	mutex_lock(&idr_lock);
	rc = idr_alloc(&dev_nums_idr, NULL, 0, TPM_NUM_DEVICES, GFP_KERNEL);
	mutex_unlock(&idr_lock);
	if (rc < 0) {
	dev_err(pdev, "No available tpm device numbers\n");
	kfree(chip);
	return ERR_PTR(rc);
	}
	chip->dev_num = rc;

	device_initialize(&chip->dev);

	chip->dev.class = tpm_class;
	chip->dev.class->shutdown_pre = tpm_class_shutdown;
	chip->dev.release = tpm_dev_release;
	chip->dev.parent = pdev;
	chip->dev.groups = chip->groups;

	if (chip->dev_num == 0)
	chip->dev.devt = MKDEV(MISC_MAJOR, TPM_MINOR);
	else
	chip->dev.devt = MKDEV(MAJOR(tpm_devt), chip->dev_num);

	rc = dev_set_name(&chip->dev, "tpm%d", chip->dev_num);
	if (rc)
	goto out;

	if (!pdev)
	chip->flags \|= TPM_CHIP_FLAG_VIRTUAL;

	cdev_init(&chip->cdev, &tpm_fops);
	chip->cdev.owner = THIS_MODULE;

	rc = tpm2_init_space(&chip->work_space, TPM2_SPACE_BUFFER_SIZE);
	if (rc) {
	rc = -ENOMEM;
	goto out;
	}

	chip->locality = -1;
	return chip;

	out:
	put_device(&chip->dev);
	return ERR_PTR(rc);
	}
	EXPORT_SYMBOL_GPL(tpm_chip_alloc);

	/**
	* tpmm_chip_alloc() - allocate a new struct tpm_chip instance
	* @pdev: parent device to which the chip is associated
	* @ops: struct tpm_class_ops instance
	*
	* Same as tpm_chip_alloc except devm is used to do the put_device
	*/
	struct tpm_chip tpmm_chip_alloc(struct device pdev,
	const struct tpm_class_ops *ops)
	{
	struct tpm_chip *chip;
	int rc;

	chip = tpm_chip_alloc(pdev, ops);
	if (IS_ERR(chip))
	return chip;

	rc = devm_add_action_or_reset(pdev,
	(void ()(void )) put_device,
	&chip->dev);
	if (rc)
	return ERR_PTR(rc);

	dev_set_drvdata(pdev, chip);

	return chip;
	}
	EXPORT_SYMBOL_GPL(tpmm_chip_alloc);

	static int tpm_add_char_device(struct tpm_chip *chip)
	{
	int rc;

	rc = cdev_device_add(&chip->cdev, &chip->dev);
	if (rc) {
	dev_err(&chip->dev,
	"unable to cdev_device_add() %s, major %d, minor %d, err=%d\n",
	dev_name(&chip->dev), MAJOR(chip->dev.devt),
	MINOR(chip->dev.devt), rc);
	return rc;
	}

	if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip)) {
	rc = tpm_devs_add(chip);
	if (rc)
	goto err_del_cdev;
	}

	/* Make the chip available. */
	mutex_lock(&idr_lock);
	idr_replace(&dev_nums_idr, chip, chip->dev_num);
	mutex_unlock(&idr_lock);

	return 0;

	err_del_cdev:
	cdev_device_del(&chip->cdev, &chip->dev);
	return rc;
	}

	static void tpm_del_char_device(struct tpm_chip *chip)
	{
	cdev_device_del(&chip->cdev, &chip->dev);

	/* Make the chip unavailable. */
	mutex_lock(&idr_lock);
	idr_replace(&dev_nums_idr, NULL, chip->dev_num);
	mutex_unlock(&idr_lock);

	/* Make the driver uncallable. */
	down_write(&chip->ops_sem);

	/*
	* Check if chip->ops is still valid: In case that the controller
	* drivers shutdown handler unregisters the controller in its
	* shutdown handler we are called twice and chip->ops to NULL.
	*/
	if (chip->ops) {
	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
	if (!tpm_chip_start(chip)) {
	tpm2_shutdown(chip, TPM2_SU_CLEAR);
	tpm_chip_stop(chip);
	}
	}
	chip->ops = NULL;
	}
	up_write(&chip->ops_sem);
	}

	static void tpm_del_legacy_sysfs(struct tpm_chip *chip)
	{
	struct attribute **i;

	if (chip->flags & (TPM_CHIP_FLAG_TPM2 \| TPM_CHIP_FLAG_VIRTUAL) \|\|
	tpm_is_firmware_upgrade(chip))
	return;

	sysfs_remove_link(&chip->dev.parent->kobj, "ppi");

	for (i = chip->groups[0]->attrs; *i != NULL; ++i)
	sysfs_remove_link(&chip->dev.parent->kobj, (*i)->name);
	}

	/* For compatibility with legacy sysfs paths we provide symlinks from the
	* parent dev directory to selected names within the tpm chip directory. Old
	* kernel versions created these files directly under the parent.
	*/
	static int tpm_add_legacy_sysfs(struct tpm_chip *chip)
	{
	struct attribute **i;
	int rc;

	if (chip->flags & (TPM_CHIP_FLAG_TPM2 \| TPM_CHIP_FLAG_VIRTUAL) \|\|
	tpm_is_firmware_upgrade(chip))
	return 0;

	rc = compat_only_sysfs_link_entry_to_kobj(
	&chip->dev.parent->kobj, &chip->dev.kobj, "ppi", NULL);
	if (rc && rc != -ENOENT)
	return rc;

	/* All the names from tpm-sysfs */
	for (i = chip->groups[0]->attrs; *i != NULL; ++i) {
	rc = compat_only_sysfs_link_entry_to_kobj(
	&chip->dev.parent->kobj, &chip->dev.kobj, (*i)->name, NULL);
	if (rc) {
	tpm_del_legacy_sysfs(chip);
	return rc;
	}
	}

	return 0;
	}

	static int tpm_hwrng_read(struct hwrng rng, void data, size_t max, bool wait)
	{
	struct tpm_chip *chip = container_of(rng, struct tpm_chip, hwrng);

	return tpm_get_random(chip, data, max);
	}

	static int tpm_add_hwrng(struct tpm_chip *chip)
	{
	if (!IS_ENABLED(CONFIG_HW_RANDOM_TPM) \|\| tpm_is_firmware_upgrade(chip))
	return 0;

	snprintf(chip->hwrng_name, sizeof(chip->hwrng_name),
	"tpm-rng-%d", chip->dev_num);
	chip->hwrng.name = chip->hwrng_name;
	chip->hwrng.read = tpm_hwrng_read;
	return hwrng_register(&chip->hwrng);
	}

	static int tpm_get_pcr_allocation(struct tpm_chip *chip)
	{
	int rc;

	if (tpm_is_firmware_upgrade(chip))
	return 0;

	rc = (chip->flags & TPM_CHIP_FLAG_TPM2) ?
	tpm2_get_pcr_allocation(chip) :
	tpm1_get_pcr_allocation(chip);

	if (rc > 0)
	return -ENODEV;

	return rc;
	}

	/*
	* tpm_chip_register() - create a character device for the TPM chip
	* @chip: TPM chip to use.
	*
	* Creates a character device for the TPM chip and adds sysfs attributes for
	* the device. As the last step this function adds the chip to the list of TPM
	* chips available for in-kernel use.
	*
	* This function should be only called after the chip initialization is
	* complete.
	*/
	int tpm_chip_register(struct tpm_chip *chip)
	{
	int rc;

	rc = tpm_chip_start(chip);
	if (rc)
	return rc;
	rc = tpm_auto_startup(chip);
	if (rc) {
	tpm_chip_stop(chip);
	return rc;
	}

	rc = tpm_get_pcr_allocation(chip);
	tpm_chip_stop(chip);
	if (rc)
	return rc;

	tpm_sysfs_add_device(chip);

	tpm_bios_log_setup(chip);

	tpm_add_ppi(chip);

	rc = tpm_add_hwrng(chip);
	if (rc)
	goto out_ppi;

	rc = tpm_add_char_device(chip);
	if (rc)
	goto out_hwrng;

	rc = tpm_add_legacy_sysfs(chip);
	if (rc) {
	tpm_chip_unregister(chip);
	return rc;
	}

	return 0;

	out_hwrng:
	if (IS_ENABLED(CONFIG_HW_RANDOM_TPM) && !tpm_is_firmware_upgrade(chip))
	hwrng_unregister(&chip->hwrng);
	out_ppi:
	tpm_bios_log_teardown(chip);

	return rc;
	}
	EXPORT_SYMBOL_GPL(tpm_chip_register);

	/*
	* tpm_chip_unregister() - release the TPM driver
	* @chip: TPM chip to use.
	*
	* Takes the chip first away from the list of available TPM chips and then
	* cleans up all the resources reserved by tpm_chip_register().
	*
	* Once this function returns the driver call backs in 'op's will not be
	* running and will no longer start.
	*
	* NOTE: This function should be only called before deinitializing chip
	* resources.
	*/
	void tpm_chip_unregister(struct tpm_chip *chip)
	{
	tpm_del_legacy_sysfs(chip);
	if (IS_ENABLED(CONFIG_HW_RANDOM_TPM) && !tpm_is_firmware_upgrade(chip))
	hwrng_unregister(&chip->hwrng);
	tpm_bios_log_teardown(chip);
	if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip))
	tpm_devs_remove(chip);
	tpm_del_char_device(chip);
	}
	EXPORT_SYMBOL_GPL(tpm_chip_unregister);