ACPI / TPM: detect PPI features by checking availability of _DSM functions

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@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 19 insertions, 26 deletions

diff --git a/drivers/char/tpm/tpm_ppi.c b/drivers/char/tpm/tpm_ppi.c
index d542ac6d0ae0..117fab6daf39 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.integer.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;