Migration guide to Zephyr v4.0.0 (Working Draft)

This document describes the changes required when migrating your application from Zephyr v3.7.0 to Zephyr v4.0.0.

Any other changes (not directly related to migrating applications) can be found in the release notes.

Build System

  • Removed the CONFIG_MCUBOOT_CMAKE_WEST_SIGN_PARAMS Kconfig option as west sign is no longer called by the build system when signing images for MCUboot.

  • The imgtool part of west sign has been deprecated, options to be supplied to imgtool when signing should be set in CONFIG_MCUBOOT_EXTRA_IMGTOOL_ARGS instead.

Kernel

  • Removed the deprecated CONFIG_MP_NUM_CPUS, application should be updated to use CONFIG_MP_MAX_NUM_CPUS instead.

Boards

  • native_posix has been deprecated in favour of native_sim (GitHub #76898).

  • Nordic nRF53 and nRF91 based boards can use the common devicetree overlays in dts/common/nordic to define default flash and ram partitioning based on TF-M.

  • STM32WBA: The command used for fetching blobs required to build ble applications is now west blobs fetch hal_stm32 instead of west blobs fetch stm32.

  • Board qemu_xtensa is deprecated. Use qemu_xtensa/dc233c instead.

Devicetree

  • The DT_REG_ADDR macro and its variants are now expanding into an unsigned literals (i.e. with a U suffix). To use addresses as devicetree indexes use the DT_REG_ADDR_RAW variants.

  • The DT_REG_SIZE macro and its variants are also expanding into unsigned literals, no raw variants are provided at this stage.

STM32

  • On all official STM32 boards, west flash selects STM32CubeProgrammer as the default west runner. If you want to enforce the selection of another runner like OpenOCD or pyOCD for flashing, you should specify it using the west --runner or -r option. (GitHub #75284)

  • ADC: Domain clock needs to be explicitly defined if property st,adc-clock-source = <ASYNC> is used.

Modules

Mbed TLS

  • The Kconfig options CONFIG_MBEDTLS_TLS_VERSION_1_0 and CONFIG_MBEDTLS_TLS_VERSION_1_1 have been removed because Mbed TLS doesn’t support TLS 1.0 and 1.1 anymore since v3.0. (GitHub #76833)

  • The following Kconfig symbols were renamed (GitHub #76408): * CONFIG_MBEDTLS_ENTROPY_ENABLED is now CONFIG_MBEDTLS_ENTROPY_C, * CONFIG_MBEDTLS_ZEPHYR_ENTROPY is now CONFIG_MBEDTLS_ENTROPY_POLL_ZEPHYR.

  • The Kconfig option CONFIG_MBEDTLS_SSL_EXPORT_KEYS was removed because the corresponding build symbol was removed in Mbed TLS 3.1.0 and is now assumed to be enabled. (GitHub #77657)

TinyCrypt

Albeit the formal deprecation of TinyCrypt is not started yet, its removal from the Zephyr codebase is. Formal deprecation will happen in the next release.

Trusted Firmware-M

  • The security counter used for the hardware rollback protection now comes explicitly from CONFIG_TFM_IMAGE_SECURITY_COUNTER, instead of being automatically determined from the image version. This has been changed as the implicit counter calculation is incompatible with versions larger than 0.0.1024 (GitHub #78128).

LVGL

zcbor

  • Updated the zcbor library to version 0.9.0. Full release notes at https://github.com/NordicSemiconductor/zcbor/blob/0.9.0/RELEASE_NOTES.md Migration guide at https://github.com/NordicSemiconductor/zcbor/blob/0.9.0/MIGRATION_GUIDE.md Migration guide copied here:

    • zcbor_simple_*() functions have been removed to avoid confusion about their use. They are still in the C file because they are used by other functions. Instead, use the specific functions for the currently supported simple values, i.e. zcbor_bool_*(), zcbor_nil_*(), and zcbor_undefined_*(). If a removed variant is strictly needed, add your own forward declaration in your code.

    • Code generation naming:

      • More C keywords are now capitalized to avoid naming collision. You might have to capitalize some instances if your code was generated to have those names.

      • A fix was made to the naming of bstr elements with a .size specifier, which might mean that these elements change name in your code when you regenerate.

Device Drivers and Devicetree

  • The compatible of the LiteX ethernet controller has been renamed from litex,eth0 to litex,liteeth. (GitHub #75433)

  • The compatible of the LiteX uart controller has been renamed from litex,uart0 to litex,uart. (GitHub #74522)

  • The devicetree bindings for the Microchip mcp23xxx series have been split up. Users of microchip,mcp230xx and microchip,mcp23sxx should change their devicetree compatible values to the specific chip variant, e.g. microchip,mcp23017. The ngpios devicetree property has been removed, since it is implied by the model name. Chip variants with open-drain outputs (mcp23x09, mcp23x18) now correctly reflect this in their driver API, users of these devices should ensure they pass appropriate values to gpio_pin_set(). (GitHub #65797)

  • The power-domain property has been removed in favor of power-domains. The new property allows to add more than one power domain. power-domain-names is also available to optionally name each entry in power-domains. The number of cells in the power-domains property need to be defined using #power-domain-cells.

Analog Digital Converter (ADC)

  • For all STM32 ADC that selects an asynchronous clock through st,adc-clock-source property, it is now mandatory to also explicitly define a domain clock source using the clock property.

Clock control

Crypto

  • Following the deprecation of the TinyCrypt library (GitHub #79566), the TinyCrypt-based shim driver was marked as deprecated (GitHub #79653).

Display

Disk

  • The SDMMC subsystem driver now requires a disk-name property be supplied with the definition of the disk, which is used when registering the SD device with the disk subsystem. This permits multiple SD devices to be registered simultaneously. If unsure, disk-name = "SD" may be used as a sane default.

  • The MMC subsystem driver now requires a disk-name property be supplied with the definition of the disk, which is used when registering the MMC device with the disk subsystem. This permits multiple MMC devices to be registered simultaneously. If unsure, disk-name = "SD2" may be used as a sane default.

Enhanced Serial Peripheral Interface (eSPI)

GNSS

  • The u-blox M10 driver has been renamed to M8 as it only supports M8 based devices. Existing devicetree compatibles should be updated to u-blox,m8, and Kconfig symbols swapped to CONFIG_GNSS_U_BLOX_M8.

  • The APIs gnss_set_periodic_config() and gnss_get_periodic_config() have been removed. (GitHub #76392)

Input

  • INPUT_CALLBACK_DEFINE has now an extra user_data void pointer argument that can be used to reference any user data structure. To restore the current behavior it can be set to NULL. A void *user_data argument has to be added to the callback function arguments.

  • The analog-axis invert property has been renamed to invert-input (there’s now an invert-output available as well).

Interrupt Controller

LED Strip

PWM

  • The Raspberry Pi Pico PWM driver now configures frequency adaptively. This has resulted in a change in how device tree parameters are handled. If the raspberry,pico-pwm’s divider-int-0 or variations for each channel are specified, or if these are set to 0, the driver dynamically configures the division ratio by specified cycles. The driver will operate at the specified division ratio if a non-zero value is specified for divider-int-0. This is unchanged from previous behavior. Please specify divider-int-0 explicitly to make the same behavior as before.

SDHC

  • The NXP USDHC driver now assumes a card is present if no card detect method is configured, instead of using the peripheral’s internal card detect signal to check for card presence. To use the internal card detect signal, the devicetree property detect-cd should be added to the USDHC node in use.

Sensors

  • The existing driver for the Microchip MCP9808 temperature sensor transformed and renamed to support all JEDEC JC 42.4 compatible temperature sensors. It now uses the jedec,jc-42.4-temp compatible string instead to the microchip,mcp9808 string.

  • The current-sense-amplifier sense resistor is now specified in milli-ohms (sense-resistor-milli-ohms) instead of micro-ohms in order to increase the maximum representable resistor from 4.2k to 4.2M.

  • The current-sense-amplifier properties sense-gain-mult and sense-gain-div are now limited to a maximum value of UINT16_MAX to enable smaller rounding errors in internal calculations.

  • The nxp, prefixed properties in nxp,kinetis-acmp have been deprecated in favor of properties without the prefix. The sensor based driver for the nxp,kinetis-acmp has been updated to support both the new and deprecated property names. Uses of the deprecated property names should be updated to the new property names.

Serial

  • Users of uart_irq_tx_ready() now need to check for ret > 0 to ensure that the FIFO can accept data bytes, instead of ret == 1. The function now returns a lower bound on the number of bytes that can be provided to uart_fifo_fill() without truncation.

  • LiteX: CONFIG_UART_LITEUART has been renamed to CONFIG_UART_LITEX.

Regulator

  • Internal regulators present in nRF52/53 series can now be configured using devicetree. The Kconfig options CONFIG_SOC_DCDC_NRF52X, CONFIG_SOC_DCDC_NRF52X_HV, CONFIG_SOC_DCDC_NRF53X_APP, CONFIG_SOC_DCDC_NRF53X_NET and CONFIG_SOC_DCDC_NRF53X_HV selected by board-level Kconfig options have been deprecated.

    Example for nRF52 series:

    /* configure REG/REG1 in DC/DC mode */
&reg/reg1 {
    regulator-initial-mode = <NRF5X_REG_MODE_DCDC>;
};

/* enable REG0 (HV mode) */
&reg0 {
    status = "okay";
};

    Example for nRF53 series:

    /* configure VREGMAIN in DC/DC mode */
&vregmain {
    regulator-initial-mode = <NRF5X_REG_MODE_DCDC>;
};

/* configure VREGRADIO in DC/DC mode */
&vregradio {
    regulator-initial-mode = <NRF5X_REG_MODE_DCDC>;
};

/* enable VREGH (HV mode) */
&vregh {
    status = "okay";
};

Bluetooth

Bluetooth HCI

  • The bt-hci-bus and bt-hci-quirks devicetree properties for HCI bindings have been changed to use lower-case strings without the BT_HCI_QUIRK_ and BT_HCI_BUS_ prefixes.

  • The Kconfig option BT_SPI is now automatically selected based on devicetree compatibles and can be removed from board .defconfig files.

Bluetooth Mesh

Bluetooth Audio

  • The Volume Renderer callback functions bt_vcp_vol_rend_cb.state and bt_vcp_vol_rend_cb.flags for VCP now contain an additional parameter for the connection. This needs to be added to all instances of VCP Volume Renderer callback functions defined. (GitHub #76992)

  • The Unicast Server has a new registration function bt_bap_unicast_server_register() which takes a bt_bap_unicast_server_register_param as argument. This allows the Unicast Server to dynamically register Source and Sink ASE count at runtime. The old CONFIG_BT_ASCS_ASE_SRC_COUNT and CONFIG_BT_ASCS_ASE_SNK_COUNT has been renamed to CONFIG_BT_ASCS_MAX_ASE_SRC_COUNT and CONFIG_BT_ASCS_MAX_ASE_SNK_COUNT to reflect that they now serve as a compile-time maximum configuration of ASEs to be used. bt_bap_unicast_server_register() needs to be called once before using the Unicast Server, and more specifically prior to calling bt_bap_unicast_server_register_cb() for the first time. It does not need to be called again until the new function bt_bap_unicast_server_unregister() has been called. (GitHub #76632)

  • The Coordinated Set Coordinator functions bt_csip_set_coordinator_lock() and bt_csip_set_coordinator_release() now require that CONFIG_BT_BONDABLE is enabled and that all members are bonded, to comply with the requirements from the CSIP spec. (GitHub #78877)

  • The callback structure provided to bt_bap_unicast_client_register_cb() is no longer const, and now multiple callback structures can be registered. (GitHub #78999)

  • The Broadcast Audio Scan Service (BASS) shall now be registered and unregistered dynamically at runtime within the scan delegator. Two new APIs, bt_bap_scan_delegator_register() and bt_bap_scan_delegator_unregister(), have been introduced to manage both BASS and scan delegator registration and initialization dynamically. It should also be mentioned that the previous callback registration function, bt_bap_scan_delegator_register_cb() has now been removed and merged with bt_bap_scan_delegator_register(). This change allows more flexibility when registering or unregistering scan delegator and BASS related functionality without requiring build-time configuration. Existing need to be updated to use these new APIs. (GitHub #78751)

  • The Telephone Bearer Service (TBS) and Generic Telephone Bearer Service (GTBS) shall now be registered dynamically at runtime with bt_tbs_register_bearer(). The services can also be unregistered with bt_tbs_unregister_bearer(). (GitHub #76108)

  • There has been a rename from bt_audio_codec_qos to bt_bap_qos_cfg. This effects all structs, enums and defines that used the bt_audio_codec_qos name. To use the new naming simply do a search-and-replace for bt_audio_codec_qos to bt_bap_qos_cfg and BT_AUDIO_CODEC_QOS to BT_BAP_QOS_CFG. (GitHub #76633)

  • The generation of broadcast ID inside of zephyr stack has been removed, it is now up the application to generate a broadcast ID. This means that the application can now fully decide whether to use a static or random broadcast ID. Reusing and statically defining a broadcast ID was added to the Basic Audio Profile in version 1.0.2, which is the basis for this change. All instances of bt_cap_initiator_broadcast_get_id() and bt_bap_broadcast_source_get_id() has been removed(GitHub #80228)

  • BT_AUDIO_BROADCAST_CODE_SIZE has been removed and BT_ISO_BROADCAST_CODE_SIZE should be used instead. (GitHub #80217)

Bluetooth Classic

Bluetooth Host

Automatic advertiser resumption is deprecated

Note

This deprecation is compiler-checked. If you get no warnings, you should not be affected.

Deprecated symbols:
New symbols:

BT_LE_ADV_OPT_CONNECTABLE is a combined instruction to make the advertiser connectable and to enable automatic resumption. To disable the automatic resumption, use BT_LE_ADV_OPT_CONN.

Extended Advertising API with shorthands

Extended Advertising API bt_le_ext_adv_* implicitly assumes BT_LE_ADV_OPT_ONE_TIME and never automatically resume advertising. Therefore, the following search/replace can be applied without thinking:

Replace all

-bt_le_ext_adv_create(BT_LE_ADV_CONN, ...)
+bt_le_ext_adv_create(BT_LE_ADV_FAST_2, ...)

-bt_le_ext_adv_update_param(..., BT_LE_ADV_CONN)
+bt_le_ext_adv_update_param(..., BT_LE_ADV_FAST_2)
Extended Advertising API with custom parameters

You may have uses of BT_LE_ADV_OPT_CONNECTABLE in assignments to a bt_le_adv_param. If your struct is never passed to bt_le_adv_start(), you should:

Legacy Advertising API not using automatic resumption

Any calls to bt_le_adv_start() that use the combination BT_LE_ADV_OPT_CONNECTABLE and BT_LE_ADV_OPT_ONE_TIME should have that combination replaced with BT_LE_ADV_OPT_CONN.

Legacy Advertising API using automatic resumption

For this case, the application has to take over the responsibility of restarting the advertiser.

Refer to the extended advertising sample for an example implementation of advertiser restarting. The same technique can be used for legacy advertising.

Bluetooth Crypto

Networking

  • The CoAP public API functions coap_get_block1_option() and coap_get_block2_option() have changed. The block_number pointer type has changed from uint8_t * to uint32_t *. Additionally, coap_get_block2_option() now accepts an additional bool *has_more parameter, to store the value of the more flag. (GitHub #76052)

  • The struct coap_transmission_parameters has a new field ack_random_percent if CONFIG_COAP_RANDOMIZE_ACK_TIMEOUT is enabled. (GitHub #79058)

  • The Ethernet bridge shell is moved under network shell. This is done so that all the network shell activities can be found under net shell command. After this change the bridge shell is used by net bridge command. (GitHub #77235)

  • The Ethernet bridging code is changed to allow similar configuration experience as in Linux. The bridged Ethernet interface can be used normally even if bridging is enabled. The actual bridging is done by a separate virtual network interface that directs network packets to bridged Ethernet interfaces. The eth_bridge_iface_allow_tx() is removed as it is not needed because the bridged Ethernet interface can send and receive data normally. The eth_bridge_listener_add() and eth_bridge_listener_remove() are removed as same functionality can be achieved using promiscuous API. Because the bridge interface is a normal network interface, the eth_bridge_iface_add() and eth_bridge_iface_remove() will take network interface pointer as a first parameter. (GitHub #77987)

  • To facilitate use outside of the networking subsystem, the network buffer header file was renamed from include/zephyr/net/buf.h to include/zephyr/net_buf.h and the implementation moved to lib/net_buf/. (GitHub #78009)

  • The work_q parameter to NET_SOCKET_SERVICE_SYNC_DEFINE and NET_SOCKET_SERVICE_SYNC_DEFINE_STATIC has been removed as it was always ignored. (GitHub #79446)

  • The callback function for the socket service has changed. The struct k_work *work parameter has been replaced with a pointer to the struct net_socket_service_event *pev parameter. (GitHub #80041)

  • Deprecated the CONFIG_NET_SOCKETS_POLL_MAX option in favour of CONFIG_ZVFS_POLL_MAX.

Other Subsystems

Flash map

hawkBit

  • hawkbit_autohandler() now takes one argument. This argument has to be set to true for the same behavior as before the change. (GitHub #71037)

  • <zephyr/mgmt/hawkbit.h> is deprecated in favor of <zephyr/mgmt/hawkbit/hawkbit.h>. The old header will be removed in future releases and its usage should be avoided. The hawkbit autohandler has been separated into <zephyr/mgmt/hawkbit/autohandler.h>. The configuration part of hawkbit is now in <zephyr/mgmt/hawkbit/config.h>. (GitHub #71037)

MCUmgr

Modem

Random

Shell

  • kernel threads and kernel stacks shell command have been renamed to kernel thread list & kernel thread stacks

JWT (JSON Web Token)

  • By default, the signature is now computed using the PSA Crypto API for both RSA and ECDSA (GitHub #78243). The conversion to the PSA Crypto API is part of the adoption of a standard interface for crypto operations (GitHub #43712). Moreover, following the deprecation of the TinyCrypt library (GitHub #79566), usage of TinyCrypt was removed from the JWT subsystem (GitHub #79653).

  • The following new symbols were added to allow specifying both the signature algorithm and crypto library:

    They replace the previously-existing Kconfigs CONFIG_JWT_SIGN_RSA and CONFIG_JWT_SIGN_ECDSA. (GitHub #79653)

Architectures