[RFC Patch v1 09/13] ACPI, TPM: detecting PPI features by checking availability of _DSM functions

From: Jiang Liu
Date: Wed Dec 18 2013 - 01:58:23 EST


Detecting physical presence interface features by checking availbility
of corresponding ACPI _DSM functions, it should be more accurate than
checking TPM version number.

Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxxxxxxx>
---
drivers/char/tpm/tpm_ppi.c | 45 +++++++++++++++++++-------------------------
1 file changed, 19 insertions(+), 26 deletions(-)

diff --git a/drivers/char/tpm/tpm_ppi.c b/drivers/char/tpm/tpm_ppi.c
index ad5143f..272c22d 100644
--- a/drivers/char/tpm/tpm_ppi.c
+++ b/drivers/char/tpm/tpm_ppi.c
@@ -23,39 +23,31 @@ static const u8 tpm_ppi_uuid[] = {
0x8D, 0x10, 0x08, 0x9D, 0x16, 0x53
};

-static char *tpm_device_name = "TPM";
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)
{
- acpi_status status = AE_OK;
- struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+ union acpi_object *obj;

- status = acpi_get_name(handle, ACPI_SINGLE_NAME, &buffer);
- if (ACPI_FAILURE(status))
+ if (!acpi_check_dsm(handle, tpm_ppi_uuid, TPM_PPI_REVISION_ID,
+ 1 << TPM_PPI_FN_VERSION))
return AE_OK;

- if (strstr(buffer.pointer, context) != NULL) {
- union acpi_object *obj;
-
- /* 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;
- status = AE_CTRL_TERMINATE;
+ /* 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);
}
- kfree(buffer.pointer);

- return status;
+ *return_value = handle;
+
+ return AE_CTRL_TERMINATE;
}

static inline union acpi_object *
@@ -118,7 +110,8 @@ static ssize_t tpm_store_ppi_request(struct device *dev,
* is updated with function index from SUBREQ to SUBREQ2 since PPI
* version 1.1
*/
- if (strcmp(tpm_ppi_version, "1.1") >= 0)
+ if (acpi_check_dsm(tpm_ppi_handle, tpm_ppi_uuid, TPM_PPI_REVISION_ID,
+ 1 << TPM_PPI_FN_SUBREQ2))
func = TPM_PPI_FN_SUBREQ2;

/*
@@ -272,7 +265,8 @@ static ssize_t show_ppi_operations(char *buf, u32 start, u32 end)
"User not required",
};

- if (strcmp(tpm_ppi_version, "1.2") < 0)
+ if (!acpi_check_dsm(tpm_ppi_handle, tpm_ppi_uuid, TPM_PPI_REVISION_ID,
+ 1 << TPM_PPI_FN_GETOPR))
return -EPERM;

tmp.type = ACPI_TYPE_INTEGER;
@@ -334,8 +328,7 @@ 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,
- tpm_device_name, &tpm_ppi_handle);
+ ppi_callback, NULL, NULL, &tpm_ppi_handle);
if (tpm_ppi_handle == NULL)
return -ENODEV;

--
1.7.10.4

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