Tss2_Tcti_Device_Init(3)

NAME
Tss2_Tcti_Device_init - Initialization function for the device TCTI library.

SYNOPSIS
#include <tcti/tcti_device.h>

TSS2_RC Tss2_Tcti_Device_Init (TSS2_TCTI_CONTEXT *tctiContext, size_t *size, const char *conf);

The Tss2_Tcti_Device_Init() function initializes a TCTI context used to communicate with the TPM device driver.

DESCRIPTION
Tss2_Tcti_Device_Init() attempts to initialize a caller allocated tctiContext of size size . Since the tctiContext must be a caller allocated buffer, the caller needs to know the size required by the TCTI library. The minimum size of this context can be discovered by providing NULL for the tctiContext and a non- NULL size parameter. The initialization function will then populate the size parameter with the minimum size of the tctiContext buffer. The caller must then allocate a buffer of this size (or larger) and call Tss2_Tcti_Device_Init () again providing the newly allocated tctiContext and the size of this context in the size parameter. This pattern is common to all TCTI initialization functions. We provide an example of this pattern using the Tss2_Tcti_Device_Init() function in the section titled EXAMPLE.

The conf parameter is a C string. If this string is NULL then the library will use a default configuration string for the caller. Alternatively, the caller may provide a configuration string that must contain the path to the device node exposed by the TPM device driver.

Once initialized, the TCTI context returned exposes the Trusted Computing Group (TCG) defined API for the lowest level communication with the TPM. Using this API the caller can exchange (send / receive) TPM2 command and response buffers with the TPM device driver. In nearly all cases however, the caller will initialize a context using this function before passing the context to a higher level API like the System API (SAPI), and then never touch it again.

TCG TSS 2.0 TPM Command Transmission Interface (TCTI) API Specification For a more thorough discussion of the TCTI API see the “TCG TSS 2.0 TPM Command Transmission Interface (TCTI) API Specification” as published by the TCG: https://trustedcomputinggroup.org/wp-content/uploads/TSS_TCTI_Version-1.0_Revision-05_Review_END030918.pdf

RETURN VALUE
A successful call to Tss2_Tcti_Device_Init() will return TSS2_RC_SUCCESS. An unsuccessful call will produce a response code described in section ERRORS.

ERRORS
TSS2_TCTI_RC_BAD_VALUE is returned if any parameters contain unexpected values. TSS2_TCTI_RC_BAD_REFERENCE is returned if any parameters are NULL when they should not be. TSS2_TCTI_RC_BAD_CONTEXT is returned if the size of the provided tctiContext is insufficient.

EXAMPLE
TCTI initialization fragment:

#include <inttypes.h>
#include <stdlib.h>
#include <stdio.h>
#include <tcti/tcti_device.h>
TSS2_RC rc;
TSS2_TCTI_CONTEXT *tcti_context;
size_t size;
char *conf = "/dev/tpm0",
rc = Tss2_Tcti_Device_Init (NULL, &size, NULL);
if (rc != TSS2_RC_SUCCESS) {
    fprintf (stderr, "Failed to get allocation size for device TCTI "
             " context: 0x%" PRIx32 ", rc);
    exit (EXIT_FAILURE);
}
tcti_context = calloc (1, size);
if (tcti_context == NULL) {
    fprintf (stderr, "Allocation for TCTI context failed: %s,
             strerror (errno));
    exit (EXIT_FAILURE);
}
rc = Tss2_Tcti_Device_Init (&tcti_context, &size, &conf);
if (rc != TSS2_RC_SUCCESS) {
    fprintf (stderr, "Failed to initialize device TCTI context: "
             "0x%" PRIx32 ", rc);
    free (tcti_context);
    exit (EXIT_FAILURE);
}
exit (EXIT_SUCCESS);