TF-M input/output control (IOCTL)

The TF-M IOTCL library provides an API for platform-specific TF-M services. These services are added by the platform partition. The APIs are available for applications that implement Non-Secure Processing Environment (NSPE) alongside Secure Processing Environment (SPE).

For more information on implementing TF-M in your application, see Running applications with Trusted Firmware-M. For more information about NSPE and SPE, see Processing environments.

Functionality

Platform-specific services are internally accessed through the tfm_platform_hal_ioctl() function. Wrapper functions for these accesses are defined in tfm_ioctl_ns_api.c and tfm_ioctl_s_api.c.

The supported platform services are defined by tfm_platform_ioctl_core_reqest_types_t in tfm_ioctl_core_api.h.

/** @brief Supported request types.
 */
enum tfm_platform_ioctl_core_reqest_types_t {
	TFM_PLATFORM_IOCTL_READ_SERVICE,
	TFM_PLATFORM_IOCTL_WRITE32_SERVICE,
	TFM_PLATFORM_IOCTL_GPIO_SERVICE,
	/* Last core service, start platform specific from this value. */
	TFM_PLATFORM_IOCTL_CORE_LAST
};

Set the CONFIG_TFM_PARTITION_PLATFORM Kconfig option to enable the services.

Read service

The TF-M IOTCL read service allows the NSPE to access memory areas within the SPE that would otherwise be inaccessible to it. The allowed memory areas are defined by the tfm_platform_user_memory_ranges.h file.

The service is used by the tfm_platform_mem_read() function. For example, you can use the service to read the OTP value from UICR registers:

#include <tfm_ioctl_api.h>

void read_otp_value(void) {
    uint32_t otp_value;
    int err;
    enum tfm_platform_err_t plt_err;

    plt_err = tfm_platform_mem_read(buf, (intptr_t)&NRF_UICR_S->OTP[0], sizeof(otp_value), &err);
    if (plt_err != TFM_PLATFORM_ERR_SUCCESS || err != 0) {
        /* Handle error */
    }

    printk("OTP[0]: %u\n", otp_value);
}

See the TF-M Hello World sample for example usage.

Prerequisites

This library requires that TF-M is installed on the device.

API documentation

Header file: include/tfm/tfm_ioctl_api.h

Source files: modules/tfm/tfm/boards/src/

TFM IOCTL API