drivers/char/tpm/tpm_ppi.c - arm/linux-arm-legacy - Git at Google

 #include <linux/acpi.h>
 #include "tpm.h"

 #define TPM_PPI_REVISION_ID	1
 #define TPM_PPI_FN_VERSION	1
 #define TPM_PPI_FN_SUBREQ	2
 #define TPM_PPI_FN_GETREQ	3
 #define TPM_PPI_FN_GETACT	4
 #define TPM_PPI_FN_GETRSP	5
 #define TPM_PPI_FN_SUBREQ2	7
 #define TPM_PPI_FN_GETOPR	8
 #define PPI_TPM_REQ_MAX		22
 #define PPI_VS_REQ_START	128
 #define PPI_VS_REQ_END		255
 #define PPI_VERSION_LEN		3

 static const u8 tpm_ppi_uuid[] = {
 	0xA6, 0xFA, 0xDD, 0x3D,
 	0x1B, 0x36,
 	0xB4, 0x4E,
 	0xA4, 0x24,
 	0x8D, 0x10, 0x08, 0x9D, 0x16, 0x53
 };

 static char tpm_ppi_version[PPI_VERSION_LEN + 1];
 static acpi_handle tpm_ppi_handle;

 static acpi_status ppi_callback(acpi_handle handle, u32 level, void *context,
 				void **return_value)
 {
 	union acpi_object *obj;

 	if (!acpi_check_dsm(handle, tpm_ppi_uuid, TPM_PPI_REVISION_ID,
 			    1 << TPM_PPI_FN_VERSION))
 		return AE_OK;

 	/* Cache version string */
 	obj = acpi_evaluate_dsm_typed(handle, tpm_ppi_uuid,
 				      TPM_PPI_REVISION_ID, TPM_PPI_FN_VERSION,
 				      NULL, ACPI_TYPE_STRING);
 	if (obj) {
 		strlcpy(tpm_ppi_version, obj->string.pointer,
 			PPI_VERSION_LEN + 1);
 		ACPI_FREE(obj);
 	}

 	*return_value = handle;

 	return AE_CTRL_TERMINATE;
 }

 static inline union acpi_object *
 tpm_eval_dsm(int func, acpi_object_type type, union acpi_object *argv4)
 {
 	BUG_ON(!tpm_ppi_handle);
 	return acpi_evaluate_dsm_typed(tpm_ppi_handle, tpm_ppi_uuid,
 				       TPM_PPI_REVISION_ID, func, argv4, type);
 }

 static ssize_t tpm_show_ppi_version(struct device *dev,
 				    struct device_attribute *attr, char *buf)
 {
 	return scnprintf(buf, PAGE_SIZE, "%s\n", tpm_ppi_version);
 }

 static ssize_t tpm_show_ppi_request(struct device *dev,
 				    struct device_attribute *attr, char *buf)
 {
 	ssize_t size = -EINVAL;
 	union acpi_object *obj;

 	obj = tpm_eval_dsm(TPM_PPI_FN_GETREQ, ACPI_TYPE_PACKAGE, NULL);
 	if (!obj)
 		return -ENXIO;

 	/*
 	 * output.pointer should be of package type, including two integers.
 	 * The first is function return code, 0 means success and 1 means
 	 * error. The second is pending TPM operation requested by the OS, 0
 	 * means none and >0 means operation value.
 	 */
 	if (obj->package.count == 2 &&
 	    obj->package.elements[0].type == ACPI_TYPE_INTEGER &&
 	    obj->package.elements[1].type == ACPI_TYPE_INTEGER) {
 		if (obj->package.elements[0].integer.value)
 			size = -EFAULT;
 		else
 			size = scnprintf(buf, PAGE_SIZE, "%llu\n",
 				 obj->package.elements[1].integer.value);
 	}

 	ACPI_FREE(obj);

 	return size;
 }

 static ssize_t tpm_store_ppi_request(struct device *dev,
 				     struct device_attribute *attr,
 				     const char *buf, size_t count)
 {
 	u32 req;
 	u64 ret;
 	int func = TPM_PPI_FN_SUBREQ;
 	union acpi_object *obj, tmp;
 	union acpi_object argv4 = ACPI_INIT_DSM_ARGV4(1, &tmp);

 	/*
 	 * the function to submit TPM operation request to pre-os environment
 	 * is updated with function index from SUBREQ to SUBREQ2 since PPI
 	 * version 1.1
 	 */
 	if (acpi_check_dsm(tpm_ppi_handle, tpm_ppi_uuid, TPM_PPI_REVISION_ID,
 			   1 << TPM_PPI_FN_SUBREQ2))
 		func = TPM_PPI_FN_SUBREQ2;

 	/*
 	 * PPI spec defines params[3].type as ACPI_TYPE_PACKAGE. Some BIOS
 	 * accept buffer/string/integer type, but some BIOS accept buffer/
 	 * string/package type. For PPI version 1.0 and 1.1, use buffer type
 	 * for compatibility, and use package type since 1.2 according to spec.
 	 */
 	if (strcmp(tpm_ppi_version, "1.2") < 0) {
 		if (sscanf(buf, "%d", &req) != 1)
 			return -EINVAL;
 		argv4.type = ACPI_TYPE_BUFFER;
 		argv4.buffer.length = sizeof(req);
 		argv4.buffer.pointer = (u8 *)&req;
 	} else {
 		tmp.type = ACPI_TYPE_INTEGER;
 		if (sscanf(buf, "%llu", &tmp.integer.value) != 1)
 			return -EINVAL;
 	}

 	obj = tpm_eval_dsm(func, ACPI_TYPE_INTEGER, &argv4);
 	if (!obj) {
 		return -ENXIO;
 	} else {
 		ret = obj->integer.value;
 		ACPI_FREE(obj);
 	}

 	if (ret == 0)
 		return (acpi_status)count;

 	return (ret == 1) ? -EPERM : -EFAULT;
 }

 static ssize_t tpm_show_ppi_transition_action(struct device *dev,
 					      struct device_attribute *attr,
 					      char *buf)
 {
 	u32 ret;
 	acpi_status status;
 	union acpi_object *obj = NULL;
 	union acpi_object tmp = {
 		.buffer.type = ACPI_TYPE_BUFFER,
 		.buffer.length = 0,
 		.buffer.pointer = NULL
 	};

 	static char *info[] = {
 		"None",
 		"Shutdown",
 		"Reboot",
 		"OS Vendor-specific",
 		"Error",
 	};

 	/*
 	 * PPI spec defines params[3].type as empty package, but some platforms
 	 * (e.g. Capella with PPI 1.0) need integer/string/buffer type, so for
 	 * compatibility, define params[3].type as buffer, if PPI version < 1.2
 	 */
 	if (strcmp(tpm_ppi_version, "1.2") < 0)
 		obj = &tmp;
 	obj = tpm_eval_dsm(TPM_PPI_FN_GETACT, ACPI_TYPE_INTEGER, obj);
 	if (!obj) {
 		return -ENXIO;
 	} else {
 		ret = obj->integer.value;
 		ACPI_FREE(obj);
 	}

 	if (ret < ARRAY_SIZE(info) - 1)
 		status = scnprintf(buf, PAGE_SIZE, "%d: %s\n", ret, info[ret]);
 	else
 		status = scnprintf(buf, PAGE_SIZE, "%d: %s\n", ret,
 				   info[ARRAY_SIZE(info)-1]);
 	return status;
 }

 static ssize_t tpm_show_ppi_response(struct device *dev,
 				     struct device_attribute *attr,
 				     char *buf)
 {
 	acpi_status status = -EINVAL;
 	union acpi_object *obj, *ret_obj;
 	u64 req, res;

 	obj = tpm_eval_dsm(TPM_PPI_FN_GETRSP, ACPI_TYPE_PACKAGE, NULL);
 	if (!obj)
 		return -ENXIO;

 	/*
 	 * parameter output.pointer should be of package type, including
 	 * 3 integers. The first means function return code, the second means
 	 * most recent TPM operation request, and the last means response to
 	 * the most recent TPM operation request. Only if the first is 0, and
 	 * the second integer is not 0, the response makes sense.
 	 */
 	ret_obj = obj->package.elements;
 	if (obj->package.count < 3 ||
 	    ret_obj[0].type != ACPI_TYPE_INTEGER ||
 	    ret_obj[1].type != ACPI_TYPE_INTEGER ||
 	    ret_obj[2].type != ACPI_TYPE_INTEGER)
 		goto cleanup;

 	if (ret_obj[0].integer.value) {
 		status = -EFAULT;
 		goto cleanup;
 	}

 	req = ret_obj[1].integer.value;
 	res = ret_obj[2].integer.value;
 	if (req) {
 		if (res == 0)
 			status = scnprintf(buf, PAGE_SIZE, "%llu %s\n", req,
 					   "0: Success");
 		else if (res == 0xFFFFFFF0)
 			status = scnprintf(buf, PAGE_SIZE, "%llu %s\n", req,
 					   "0xFFFFFFF0: User Abort");
 		else if (res == 0xFFFFFFF1)
 			status = scnprintf(buf, PAGE_SIZE, "%llu %s\n", req,
 					   "0xFFFFFFF1: BIOS Failure");
 		else if (res >= 1 && res <= 0x00000FFF)
 			status = scnprintf(buf, PAGE_SIZE, "%llu %llu: %s\n",
 					   req, res, "Corresponding TPM error");
 		else
 			status = scnprintf(buf, PAGE_SIZE, "%llu %llu: %s\n",
 					   req, res, "Error");
 	} else {
 		status = scnprintf(buf, PAGE_SIZE, "%llu: %s\n",
 				   req, "No Recent Request");
 	}

 cleanup:
 	ACPI_FREE(obj);
 	return status;
 }

 static ssize_t show_ppi_operations(char *buf, u32 start, u32 end)
 {
 	int i;
 	u32 ret;
 	char *str = buf;
 	union acpi_object *obj, tmp;
 	union acpi_object argv = ACPI_INIT_DSM_ARGV4(1, &tmp);

 	static char *info[] = {
 		"Not implemented",
 		"BIOS only",
 		"Blocked for OS by BIOS",
 		"User required",
 		"User not required",
 	};

 	if (!acpi_check_dsm(tpm_ppi_handle, tpm_ppi_uuid, TPM_PPI_REVISION_ID,
 			    1 << TPM_PPI_FN_GETOPR))
 		return -EPERM;

 	tmp.integer.type = ACPI_TYPE_INTEGER;
 	for (i = start; i <= end; i++) {
 		tmp.integer.value = i;
 		obj = tpm_eval_dsm(TPM_PPI_FN_GETOPR, ACPI_TYPE_INTEGER, &argv);
 		if (!obj) {
 			return -ENOMEM;
 		} else {
 			ret = obj->integer.value;
 			ACPI_FREE(obj);
 		}

 		if (ret > 0 && ret < ARRAY_SIZE(info))
 			str += scnprintf(str, PAGE_SIZE, "%d %d: %s\n",
 					 i, ret, info[ret]);
 	}

 	return str - buf;
 }

 static ssize_t tpm_show_ppi_tcg_operations(struct device *dev,
 					   struct device_attribute *attr,
 					   char *buf)
 {
 	return show_ppi_operations(buf, 0, PPI_TPM_REQ_MAX);
 }

 static ssize_t tpm_show_ppi_vs_operations(struct device *dev,
 					  struct device_attribute *attr,
 					  char *buf)
 {
 	return show_ppi_operations(buf, PPI_VS_REQ_START, PPI_VS_REQ_END);
 }

 static DEVICE_ATTR(version, S_IRUGO, tpm_show_ppi_version, NULL);
 static DEVICE_ATTR(request, S_IRUGO | S_IWUSR | S_IWGRP,
 		   tpm_show_ppi_request, tpm_store_ppi_request);
 static DEVICE_ATTR(transition_action, S_IRUGO,
 		   tpm_show_ppi_transition_action, NULL);
 static DEVICE_ATTR(response, S_IRUGO, tpm_show_ppi_response, NULL);
 static DEVICE_ATTR(tcg_operations, S_IRUGO, tpm_show_ppi_tcg_operations, NULL);
 static DEVICE_ATTR(vs_operations, S_IRUGO, tpm_show_ppi_vs_operations, NULL);

 static struct attribute *ppi_attrs[] = {
 	&dev_attr_version.attr,
 	&dev_attr_request.attr,
 	&dev_attr_transition_action.attr,
 	&dev_attr_response.attr,
 	&dev_attr_tcg_operations.attr,
 	&dev_attr_vs_operations.attr, NULL,
 };
 static struct attribute_group ppi_attr_grp = {
 	.name = "ppi",
 	.attrs = ppi_attrs
 };

 int tpm_add_ppi(struct kobject *parent)
 {
 	/* Cache TPM ACPI handle and version string */
 	acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT, ACPI_UINT32_MAX,
 			    ppi_callback, NULL, NULL, &tpm_ppi_handle);
 	if (tpm_ppi_handle == NULL)
 		return -ENODEV;

 	return sysfs_create_group(parent, &ppi_attr_grp);
 }

 void tpm_remove_ppi(struct kobject *parent)
 {
 	sysfs_remove_group(parent, &ppi_attr_grp);
 }
	#include <linux/acpi.h>
	#include "tpm.h"

	#define TPM_PPI_REVISION_ID 1
	#define TPM_PPI_FN_VERSION 1
	#define TPM_PPI_FN_SUBREQ 2
	#define TPM_PPI_FN_GETREQ 3
	#define TPM_PPI_FN_GETACT 4
	#define TPM_PPI_FN_GETRSP 5
	#define TPM_PPI_FN_SUBREQ2 7
	#define TPM_PPI_FN_GETOPR 8
	#define PPI_TPM_REQ_MAX 22
	#define PPI_VS_REQ_START 128
	#define PPI_VS_REQ_END 255
	#define PPI_VERSION_LEN 3

	static const u8 tpm_ppi_uuid[] = {
	0xA6, 0xFA, 0xDD, 0x3D,
	0x1B, 0x36,
	0xB4, 0x4E,
	0xA4, 0x24,
	0x8D, 0x10, 0x08, 0x9D, 0x16, 0x53
	};

	static char tpm_ppi_version[PPI_VERSION_LEN + 1];
	static acpi_handle tpm_ppi_handle;

	static acpi_status ppi_callback(acpi_handle handle, u32 level, void *context,
	void **return_value)
	{
	union acpi_object *obj;

	if (!acpi_check_dsm(handle, tpm_ppi_uuid, TPM_PPI_REVISION_ID,
	1 << TPM_PPI_FN_VERSION))
	return AE_OK;

	/* Cache version string */
	obj = acpi_evaluate_dsm_typed(handle, tpm_ppi_uuid,
	TPM_PPI_REVISION_ID, TPM_PPI_FN_VERSION,
	NULL, ACPI_TYPE_STRING);
	if (obj) {
	strlcpy(tpm_ppi_version, obj->string.pointer,
	PPI_VERSION_LEN + 1);
	ACPI_FREE(obj);
	}

	*return_value = handle;

	return AE_CTRL_TERMINATE;
	}

	static inline union acpi_object *
	tpm_eval_dsm(int func, acpi_object_type type, union acpi_object *argv4)
	{
	BUG_ON(!tpm_ppi_handle);
	return acpi_evaluate_dsm_typed(tpm_ppi_handle, tpm_ppi_uuid,
	TPM_PPI_REVISION_ID, func, argv4, type);
	}

	static ssize_t tpm_show_ppi_version(struct device *dev,
	struct device_attribute attr, char buf)
	{
	return scnprintf(buf, PAGE_SIZE, "%s\n", tpm_ppi_version);
	}

	static ssize_t tpm_show_ppi_request(struct device *dev,
	struct device_attribute attr, char buf)
	{
	ssize_t size = -EINVAL;
	union acpi_object *obj;

	obj = tpm_eval_dsm(TPM_PPI_FN_GETREQ, ACPI_TYPE_PACKAGE, NULL);
	if (!obj)
	return -ENXIO;

	/*
	* output.pointer should be of package type, including two integers.
	* The first is function return code, 0 means success and 1 means
	* error. The second is pending TPM operation requested by the OS, 0
	* means none and >0 means operation value.
	*/
	if (obj->package.count == 2 &&
	obj->package.elements[0].type == ACPI_TYPE_INTEGER &&
	obj->package.elements[1].type == ACPI_TYPE_INTEGER) {
	if (obj->package.elements[0].integer.value)
	size = -EFAULT;
	else
	size = scnprintf(buf, PAGE_SIZE, "%llu\n",
	obj->package.elements[1].integer.value);
	}

	ACPI_FREE(obj);

	return size;
	}

	static ssize_t tpm_store_ppi_request(struct device *dev,
	struct device_attribute *attr,
	const char *buf, size_t count)
	{
	u32 req;
	u64 ret;
	int func = TPM_PPI_FN_SUBREQ;
	union acpi_object *obj, tmp;
	union acpi_object argv4 = ACPI_INIT_DSM_ARGV4(1, &tmp);

	/*
	* the function to submit TPM operation request to pre-os environment
	* is updated with function index from SUBREQ to SUBREQ2 since PPI
	* version 1.1
	*/
	if (acpi_check_dsm(tpm_ppi_handle, tpm_ppi_uuid, TPM_PPI_REVISION_ID,
	1 << TPM_PPI_FN_SUBREQ2))
	func = TPM_PPI_FN_SUBREQ2;

	/*
	* PPI spec defines params[3].type as ACPI_TYPE_PACKAGE. Some BIOS
	* accept buffer/string/integer type, but some BIOS accept buffer/
	* string/package type. For PPI version 1.0 and 1.1, use buffer type
	* for compatibility, and use package type since 1.2 according to spec.
	*/
	if (strcmp(tpm_ppi_version, "1.2") < 0) {
	if (sscanf(buf, "%d", &req) != 1)
	return -EINVAL;
	argv4.type = ACPI_TYPE_BUFFER;
	argv4.buffer.length = sizeof(req);
	argv4.buffer.pointer = (u8 *)&req;
	} else {
	tmp.type = ACPI_TYPE_INTEGER;
	if (sscanf(buf, "%llu", &tmp.integer.value) != 1)
	return -EINVAL;
	}

	obj = tpm_eval_dsm(func, ACPI_TYPE_INTEGER, &argv4);
	if (!obj) {
	return -ENXIO;
	} else {
	ret = obj->integer.value;
	ACPI_FREE(obj);
	}

	if (ret == 0)
	return (acpi_status)count;

	return (ret == 1) ? -EPERM : -EFAULT;
	}

	static ssize_t tpm_show_ppi_transition_action(struct device *dev,
	struct device_attribute *attr,
	char *buf)
	{
	u32 ret;
	acpi_status status;
	union acpi_object *obj = NULL;
	union acpi_object tmp = {
	.buffer.type = ACPI_TYPE_BUFFER,
	.buffer.length = 0,
	.buffer.pointer = NULL
	};

	static char *info[] = {
	"None",
	"Shutdown",
	"Reboot",
	"OS Vendor-specific",
	"Error",
	};

	/*
	* PPI spec defines params[3].type as empty package, but some platforms
	* (e.g. Capella with PPI 1.0) need integer/string/buffer type, so for
	* compatibility, define params[3].type as buffer, if PPI version < 1.2
	*/
	if (strcmp(tpm_ppi_version, "1.2") < 0)
	obj = &tmp;
	obj = tpm_eval_dsm(TPM_PPI_FN_GETACT, ACPI_TYPE_INTEGER, obj);
	if (!obj) {
	return -ENXIO;
	} else {
	ret = obj->integer.value;
	ACPI_FREE(obj);
	}

	if (ret < ARRAY_SIZE(info) - 1)
	status = scnprintf(buf, PAGE_SIZE, "%d: %s\n", ret, info[ret]);
	else
	status = scnprintf(buf, PAGE_SIZE, "%d: %s\n", ret,
	info[ARRAY_SIZE(info)-1]);
	return status;
	}

	static ssize_t tpm_show_ppi_response(struct device *dev,
	struct device_attribute *attr,
	char *buf)
	{
	acpi_status status = -EINVAL;
	union acpi_object obj, ret_obj;
	u64 req, res;

	obj = tpm_eval_dsm(TPM_PPI_FN_GETRSP, ACPI_TYPE_PACKAGE, NULL);
	if (!obj)
	return -ENXIO;

	/*
	* parameter output.pointer should be of package type, including
	* 3 integers. The first means function return code, the second means
	* most recent TPM operation request, and the last means response to
	* the most recent TPM operation request. Only if the first is 0, and
	* the second integer is not 0, the response makes sense.
	*/
	ret_obj = obj->package.elements;
	if (obj->package.count < 3 \|\|
	ret_obj[0].type != ACPI_TYPE_INTEGER \|\|
	ret_obj[1].type != ACPI_TYPE_INTEGER \|\|
	ret_obj[2].type != ACPI_TYPE_INTEGER)
	goto cleanup;

	if (ret_obj[0].integer.value) {
	status = -EFAULT;
	goto cleanup;
	}

	req = ret_obj[1].integer.value;
	res = ret_obj[2].integer.value;
	if (req) {
	if (res == 0)
	status = scnprintf(buf, PAGE_SIZE, "%llu %s\n", req,
	"0: Success");
	else if (res == 0xFFFFFFF0)
	status = scnprintf(buf, PAGE_SIZE, "%llu %s\n", req,
	"0xFFFFFFF0: User Abort");
	else if (res == 0xFFFFFFF1)
	status = scnprintf(buf, PAGE_SIZE, "%llu %s\n", req,
	"0xFFFFFFF1: BIOS Failure");
	else if (res >= 1 && res <= 0x00000FFF)
	status = scnprintf(buf, PAGE_SIZE, "%llu %llu: %s\n",
	req, res, "Corresponding TPM error");
	else
	status = scnprintf(buf, PAGE_SIZE, "%llu %llu: %s\n",
	req, res, "Error");
	} else {
	status = scnprintf(buf, PAGE_SIZE, "%llu: %s\n",
	req, "No Recent Request");
	}

	cleanup:
	ACPI_FREE(obj);
	return status;
	}

	static ssize_t show_ppi_operations(char *buf, u32 start, u32 end)
	{
	int i;
	u32 ret;
	char *str = buf;
	union acpi_object *obj, tmp;
	union acpi_object argv = ACPI_INIT_DSM_ARGV4(1, &tmp);

	static char *info[] = {
	"Not implemented",
	"BIOS only",
	"Blocked for OS by BIOS",
	"User required",
	"User not required",
	};

	if (!acpi_check_dsm(tpm_ppi_handle, tpm_ppi_uuid, TPM_PPI_REVISION_ID,
	1 << TPM_PPI_FN_GETOPR))
	return -EPERM;

	tmp.integer.type = ACPI_TYPE_INTEGER;
	for (i = start; i <= end; i++) {
	tmp.integer.value = i;
	obj = tpm_eval_dsm(TPM_PPI_FN_GETOPR, ACPI_TYPE_INTEGER, &argv);
	if (!obj) {
	return -ENOMEM;
	} else {
	ret = obj->integer.value;
	ACPI_FREE(obj);
	}

	if (ret > 0 && ret < ARRAY_SIZE(info))
	str += scnprintf(str, PAGE_SIZE, "%d %d: %s\n",
	i, ret, info[ret]);
	}

	return str - buf;
	}

	static ssize_t tpm_show_ppi_tcg_operations(struct device *dev,
	struct device_attribute *attr,
	char *buf)
	{
	return show_ppi_operations(buf, 0, PPI_TPM_REQ_MAX);
	}

	static ssize_t tpm_show_ppi_vs_operations(struct device *dev,
	struct device_attribute *attr,
	char *buf)
	{
	return show_ppi_operations(buf, PPI_VS_REQ_START, PPI_VS_REQ_END);
	}

	static DEVICE_ATTR(version, S_IRUGO, tpm_show_ppi_version, NULL);
	static DEVICE_ATTR(request, S_IRUGO \| S_IWUSR \| S_IWGRP,
	tpm_show_ppi_request, tpm_store_ppi_request);
	static DEVICE_ATTR(transition_action, S_IRUGO,
	tpm_show_ppi_transition_action, NULL);
	static DEVICE_ATTR(response, S_IRUGO, tpm_show_ppi_response, NULL);
	static DEVICE_ATTR(tcg_operations, S_IRUGO, tpm_show_ppi_tcg_operations, NULL);
	static DEVICE_ATTR(vs_operations, S_IRUGO, tpm_show_ppi_vs_operations, NULL);

	static struct attribute *ppi_attrs[] = {
	&dev_attr_version.attr,
	&dev_attr_request.attr,
	&dev_attr_transition_action.attr,
	&dev_attr_response.attr,
	&dev_attr_tcg_operations.attr,
	&dev_attr_vs_operations.attr, NULL,
	};
	static struct attribute_group ppi_attr_grp = {
	.name = "ppi",
	.attrs = ppi_attrs
	};

	int tpm_add_ppi(struct kobject *parent)
	{
	/* Cache TPM ACPI handle and version string */
	acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT, ACPI_UINT32_MAX,
	ppi_callback, NULL, NULL, &tpm_ppi_handle);
	if (tpm_ppi_handle == NULL)
	return -ENODEV;

	return sysfs_create_group(parent, &ppi_attr_grp);
	}

	void tpm_remove_ppi(struct kobject *parent)
	{
	sysfs_remove_group(parent, &ppi_attr_grp);
	}