---
name: "Tss2_Tcti_Device_Init"
section: "3"
platform: "linux"
package: "tpm2-tss"
version: "4.2.0-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/Tss2_Tcti_Device_Init"
---

# Tss2\_Tcti\_Device\_Init(3)

Initialization function for the device TCTI library.

## 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 "0, rc);
    exit (EXIT_FAILURE);
}
tcti_context = calloc (1, size);
if (tcti_context == NULL) {
    fprintf (stderr, "Allocation for TCTI context failed: %s0,
             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 "0, rc);
    free (tcti_context);
    exit (EXIT_FAILURE);
}
exit (EXIT_SUCCESS);
```

## AUTHOR

TPM2 Software Project \<https://github.com/tpm2-software/tpm2-tss\>

## SEE ALSO

[**Tss2\_Tcti\_Device\_Init**(3)](/Tss2_Tcti_Device_Init/3.md), **Tss2\_Tcti\_Socket\_Init**(3), [**Tss2\_TctiLdr\_Initialize**(3)](/Tss2_TctiLdr_Initialize/3.md), [**Tss2\_TctiLdr\_Finalize**(3)](/Tss2_TctiLdr_Finalize/3.md), **tcti-device**(7), **tcti-socket**(7), **tcti-tabrmd**(7), [**tpm2-abrmd**(8)](/tpm2-abrmd/8.md)

## COLOPHON

This page is part of release 4.2.0 of Open Source implementation of the TCG TPM2 Software Stack (TSS2). A description of the project, information about reporting bugs, and the latest version of this page can be found at https://github.com/tpm2-software/tpm2-tss/.

## LICENSE

This work is licensed under the Creative Commons Attribution 4.0 International License (CC BY 4.0). For more information visit https://creativecommons.org/licenses/by/4.0/