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 

Kernel 

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.

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)

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)

Trusted Firmware-M 

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)

Controller Area Network (CAN)

Display 

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 

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.

Serial 

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 

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 specfically 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)

Bluetooth Classic 

Bluetooth Host 

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 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)

Other Subsystems 

Flash map 

CONFIG_SPI_NOR_IDLE_IN_DPD has been removed from the CONFIG_SPI_NOR driver. An enhanced version of this functionality can be obtained by enabling Device Runtime Power Management on the device (Tunable with CONFIG_SPI_NOR_ACTIVE_DWELL_MS).

hawkBit 

MCUmgr 

Modem 

Shell 

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