Migration guide to Zephyr v3.6.0

This document describes the changes required when migrating your application from Zephyr v3.5.0 to Zephyr v3.6.0.

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

Build System

  • The deprecated prj_<board>.conf Kconfig file support has been removed, projects that use this should switch to using board Kconfig fragments instead (boards/<board>.conf).

  • Until now _POSIX_C_SOURCE, _XOPEN_SOURCE, and _XOPEN_SOURCE_EXTENDED were defined globally when building for the native (ARCH_POSIX) targets, and _POSIX_C_SOURCE when building with PicolibC. Since this release, these are set only for the files that need them. If your library or application needed this, you may start getting an “implicit declaration” warning for functions whose prototypes are only exposed if one of these is defined. If so, you can fix it by defining the corresponding macro in your C source file before any include, or by adding the equivalent of target_compile_definitions(app PRIVATE _POSIX_C_SOURCE=200809L) to your application or zephyr_library_compile_definitions(_POSIX_C_SOURCE=200809L) to your library.

  • Build type by setting CONF_FILE to prj_<build>.conf is now deprecated, users should instead use the new -DFILE_SUFFIX feature File Suffixes.


  • The system heap size and its availability is now determined by a K_HEAP_MEM_POOL_SIZE define instead of the CONFIG_HEAP_MEM_POOL_SIZE Kconfig option. Subsystems can specify their own custom system heap size requirements by specifying Kconfig options with the prefix CONFIG_HEAP_MEM_POOL_ADD_SIZE_. The old Kconfig option still exists, but will be overridden if the custom requirements are larger. To force the old Kconfig option to be used, even when its value is less than the indicated custom requirements, a new CONFIG_HEAP_MEM_POOL_IGNORE_MIN option has been introduced (which defaults being disabled).


  • The deprecated Nordic SoC Kconfig option NRF_STORE_REBOOT_TYPE_GPREGRET has been removed, applications that use this should switch to using the Boot mode instead.

  • NXP: Enabled linkserver to be the default runner on the following NXP boards: mimxrt685_evk_cm33, frdm_k64f, mimxrt1050_evk, frdm_kl25z, mimxrt1020_evk, mimxrt1015_evk


Optional Modules

The following modules have been made optional and are not downloaded with west update by default anymore:

To enable them again use the west config manifest.project-filter -- +<module name> command, or west config manifest.group-filter -- +optional to enable all optional modules, and then run west update again.


  • MCUboot’s deprecated CONFIG_ZEPHYR_TRY_MASS_ERASE Kconfig option has been removed. If an erase is needed when flashing MCUboot, this should now be provided directly to the west command e.g. west flash --erase. (GitHub #64703)


  • If you have zcbor-generated code that relies on the zcbor libraries through Zephyr, you must regenerate the files using zcbor 0.8.1. Note that the names of generated types and members has been overhauled, so the code using the generated code must likely be changed. For example:

    • Leading single underscores and all double underscores are largely gone,

    • Names sometimes gain suffixes like _m or _l for disambiguation.

    • All enum (choice) names have now gained a _c suffix, so the enum name no longer matches the corresponding member name exactly (because this broke C++ namespace rules).

  • The function zcbor_new_state(), zcbor_new_decode_state() and the macro ZCBOR_STATE_D have gained new parameters related to decoding of unordered maps. Unless you are using that new functionality, these can all be set to NULL or 0.

  • The functions zcbor_bstr_put_term() and zcbor_tstr_put_term() have gained a new parameter maxlen, referring to the maximum length of the parameter str. This parameter is passed directly to strnlen() under the hood.

  • The function zcbor_tag_encode() has been renamed to zcbor_tag_put().

  • Printing has been changed significantly, e.g. zcbor_print() is now called zcbor_log(), and zcbor_trace() with no parameters is gone, and in its place are zcbor_trace_file() and zcbor_trace(), both of which take a state parameter.

Device Drivers and Devicetree

Devicetree Labels

  • Various deprecated macros related to the deprecated devicetree label property were removed. These are listed in the following table. The table also provides replacements.

    However, if you are still using code like device_get_binding(DT_LABEL(node_id)), consider replacing it with something like DEVICE_DT_GET(node_id) instead. The DEVICE_DT_GET() macro avoids run-time string comparisons, and is also safer because it will fail the build if the device does not exist.

    Removed macro


    DT_GPIO_LABEL(node_id, gpio_pha)

    DT_PROP(DT_GPIO_CTLR(node_id, gpio_pha), label)

    DT_GPIO_LABEL_BY_IDX(node_id, gpio_pha, idx)

    DT_PROP(DT_GPIO_CTLR_BY_IDX(node_id, gpio_pha, idx), label)

    DT_INST_GPIO_LABEL(inst, gpio_pha)

    DT_PROP(DT_GPIO_CTLR(DT_DRV_INST(inst), gpio_pha), label)

    DT_INST_GPIO_LABEL_BY_IDX(inst, gpio_pha, idx)

    DT_PROP(DT_GPIO_CTLR_BY_IDX(DT_DRV_INST(inst), gpio_pha, idx), label)


    DT_PROP(DT_SPI_DEV_CS_GPIOS_CTLR(spi_dev), label)




    DT_PROP(node_id, label)


    DT_PROP(DT_BUS(node_id), label)


    DT_INST_PROP(inst, label)


    DT_PROP(DT_BUS(DT_DRV_INST(inst)), label)

Multi-level Interrupts

  • For platforms that enabled CONFIG_MULTI_LEVEL_INTERRUPTS, the IRQ variant of the Devicetree macros now return the as-seen value in the devicetree instead of the Zephyr multilevel-encoded IRQ number. To get the IRQ number in Zephyr multilevel-encoded format, use IRQN variant instead. For example, consider the following devicetree:

    plic: interrupt-controller@c000000 {
            riscv,max-priority = <7>;
            riscv,ndev = <1024>;
            reg = <0x0c000000 0x04000000>;
            interrupts-extended = <&hlic0 11>;
            compatible = "sifive,plic-1.0.0";
            #address-cells = <0x0>;
            #interrupt-cells = <0x2>;
    uart0: uart@10000000 {
            interrupts = <10 1>;
            interrupt-parent = <&plic>;
            clock-frequency = <0x384000>;
            reg = <0x10000000 0x100>;
            compatible = "ns16550";
            reg-shift = <0>;

    plic is a second level interrupt aggregator and uart0 is a child of plic. DT_IRQ_BY_IDX(DT_NODELABEL(uart0), 0, irq) will return 10 (as-seen value in the devicetree), while DT_IRQN_BY_IDX(DT_NODELABEL(uart0), 0) will return (((10 + 1) << CONFIG_1ST_LEVEL_INTERRUPT_BITS) | 11).

    Drivers and applications that are supposed to work in multilevel-interrupt configurations should be updated to use the IRQN variant, i.e.:

    • DT_IRQ(node_id, irq) -> DT_IRQN(node_id)

    • DT_IRQ_BY_IDX(node_id, idx, irq) -> DT_IRQN_BY_IDX(node_id, idx)

    • DT_IRQ_BY_NAME(node_id, name, irq) -> DT_IRQN_BY_NAME(node_id, name)

    • DT_INST_IRQ(inst, irq) -> DT_INST_IRQN(inst)

    • DT_INST_IRQ_BY_IDX(inst, idx, irq) -> DT_INST_IRQN_BY_IDX(inst, idx)

    • DT_INST_IRQ_BY_NAME(inst, name, irq) -> DT_INST_IRQN_BY_NAME(inst, name)

Analog-to-Digital Converter (ADC)

Bluetooth HCI

Controller Area Network (CAN)

  • The native Linux SocketCAN driver, which can now be used in both native_posix and native_sim with or without an embedded C-library, has been renamed to reflect this:

  • Two new structures for holding common CAN controller driver configuration (struct can_driver_config) and data (struct can_driver_data) fields were introduced. Out-of-tree CAN controller drivers need to be updated to use these new, common configuration and data structures along with their initializer macros.

  • The optional can_get_max_bitrate_t CAN controller driver callback was removed in favor of a common accessor function. Out-of-tree CAN controller drivers need to be updated to no longer supply this callback.

  • The CAN transceiver API function can_transceiver_enable() now takes a can_mode_t argument for propagating the CAN controller operational mode to the CAN transceiver. Out-of-tree CAN controller and CAN transceiver drivers need to be updated to match this new API function signature.

  • The CAN_FILTER_FDF flag for filtering classic CAN/CAN FD frames was removed since no known CAN controllers implement support for this. Applications can still filter on classic CAN/CAN FD frames in their receive callback functions as needed.

  • The CAN_FILTER_DATA and CAN_FILTER_RTR flags for filtering between Data and Remote Transmission Request (RTR) frames were removed since not all CAN controllers implement support for individual RX filtering based on the RTR bit. Applications can now use CONFIG_CAN_ACCEPT_RTR to either accept incoming RTR frames matching CAN filters or reject all incoming CAN RTR frames (the default). When CONFIG_CAN_ACCEPT_RTR is enabled, applications can still filter between Data and RTR frames in their receive callback functions as needed.

  • The st,stm32h7-fdcan CAN controller driver now supports configuring the domain/kernel clock via devicetree. Previously, the driver only supported using the PLL1_Q clock for kernel clock, but now it defaults to the HSE clock, which is the chip default. Boards that use the PLL1_Q clock for FDCAN will need to override the clocks property as follows:

    &fdcan1 {
            clocks = <&rcc STM32_CLOCK_BUS_APB1_2 0x00000100>,
                     <&rcc STM32_SRC_PLL1_Q FDCAN_SEL(1)>;


  • ILI9XXX based displays now use the MIPI DBI driver class. These displays must now be declared within a MIPI DBI driver wrapper device, which will manage interfacing with the display. Note that the cmd-data-gpios pin has changed polarity with this update, to align better with the new dc-gpios name. For an example, see below:

    /* Legacy ILI9XXX display definition */
    &spi2 {
        ili9340: ili9340@0 {
            compatible = "ilitek,ili9340";
            reg = <0>;
            spi-max-frequency = <32000000>;
            reset-gpios = <&gpio0 6 GPIO_ACTIVE_LOW>;
            cmd-data-gpios = <&gpio0 12 GPIO_ACTIVE_LOW>;
            rotation = <270>;
            width = <320>;
            height = <240>;
    /* New display definition with MIPI DBI device */
    mipi_dbi {
        compatible = "zephyr,mipi-dbi-spi";
        reset-gpios = <&gpio0 6 GPIO_ACTIVE_LOW>;
        dc-gpios = <&gpio0 12 GPIO_ACTIVE_HIGH>;
        spi-dev = <&spi2>;
        #address-cells = <1>;
        #size-cells = <0>;
        ili9340: ili9340@0 {
            compatible = "ilitek,ili9340";
            reg = <0>;
            mipi-max-frequency = <32000000>;
            rotation = <270>;
            width = <320>;
            height = <240>;


  • The st,stm32-ospi-nor and st,stm32-qspi-nor give the nor flash base address and size (in Bytes) with the reg property as follows. The <size> property is not used anymore.

    mx25lm51245: ospi-nor-flash@70000000 {
            compatible = "st,stm32-ospi-nor";
            reg = <0x70000000 DT_SIZE_M(64)>; /* 512 Mbits*/

General Purpose I/O (GPIO)

  • The nxp,pcf8574 driver has been renamed to nxp,pcf857x. (GitHub #67054) to support pcf8574 and pcf8575. The Kconfig option has been renamed from CONFIG_GPIO_PCF8574 to CONFIG_GPIO_PCF857X. The Device Tree can be configured as follows:

    &i2c {
      status = "okay";
      pcf8574: pcf857x@20 {
          compatible = "nxp,pcf857x";
          status = "okay";
          reg = <0x20>;
          #gpio-cells = <2>;
          ngpios = <8>;
      pcf8575: pcf857x@21 {
          compatible = "nxp,pcf857x";
          status = "okay";
          reg = <0x21>;
          #gpio-cells = <2>;
          ngpios = <16>;


Interrupt Controller

  • The function signature of the isr_t callback function passed to the shared_irq interrupt controller driver API via shared_irq_isr_register() has changed. The callback now takes an additional irq_number parameter. Out-of-tree users of this API will need to be updated.

    (GitHub #66427)

Renesas RA Series Drivers


  • The st,lsm6dsv16x sensor driver has been changed to support configuration of both int1 and int2 pins. The DT attribute irq-gpios has been removed and substituted by two new attributes, int1-gpios and int2-gpios. These attributes must be configured in the Device Tree similarly to the following example:

    / {
        lsm6dsv16x@0 {
            compatible = "st,lsm6dsv16x";
            int1-gpios = <&gpioa 4 GPIO_ACTIVE_HIGH>;
            int2-gpios = <&gpiod 11 GPIO_ACTIVE_HIGH>;
            drdy-pin = <2>;


  • Runtime configuration is now disabled by default for Nordic UART drivers. The motivation for the change is that this feature is rarely used and disabling it significantly reduces the memory footprint.


  • The st,stm32-lptim lptim which is selected for counting ticks during low power modes is identified by stm32_lp_tick_source in the device tree as follows. The stm32_lptim_timer driver has been changed to support this.

    stm32_lp_tick_source: &lptim1 {
            status = "okay";


  • ATT now has its own TX buffer pool. If extra ATT buffers were configured using CONFIG_BT_L2CAP_TX_BUF_COUNT, they now instead should be configured through CONFIG_BT_ATT_TX_COUNT.

  • The HCI implementation for both the Host and the Controller sides has been renamed for the IPC transport. The CONFIG_BT_RPMSG Kconfig option is now CONFIG_BT_HCI_IPC, and the zephyr,bt-hci-rpmsg-ipc Devicetree chosen is now zephyr,bt-hci-ipc. The existing sample has also been renamed, from samples/bluetooth/hci_rpmsg to samples/bluetooth/hci_ipc. (GitHub #64391)

  • The BT GATT callback list, appended to by bt_gatt_cb_register(), is no longer cleared on bt_enable(). Callbacks can now be registered before the initial call to bt_enable(), and should no longer be re-registered after a bt_disable() bt_enable() cycle. (GitHub #63693)

  • The Bluetooth UUID has been modified to rodata in BT_UUID_DECLARE_16, BT_UUID_DECLARE_32 and BT_UUID_DECLARE_128 as the return value has been changed to const. Any pointer to a UUID must be prefixed with const, otherwise there will be a compilation warning. For example change struct bt_uuid *uuid = BT_UUID_DECLARE_16(xx) to const struct bt_uuid *uuid = BT_UUID_DECLARE_16(xx). (GitHub #66136)

  • The bt_l2cap_chan_send() API no longer allocates buffers from the same pool as its buf parameter when segmenting SDUs into PDUs. In order to reproduce the previous behavior, the application should register the alloc_seg channel callback and allocate from the same pool as buf.

  • The bt_l2cap_chan_send() API now requires the application to reserve enough bytes for the L2CAP headers. Call net_buf_reserve(buf, BT_L2CAP_SDU_CHAN_SEND_RESERVE); at buffer allocation time to do so.

  • BT_ISO_TIMESTAMP_NONE has been removed and the ts parameter of bt_iso_chan_send() has as well. bt_iso_chan_send() now always sends without timestamp. To send with a timestamp, bt_iso_chan_send_ts() can be used.

Bluetooth Mesh

Bluetooth Audio

  • The BT_AUDIO_CODEC_LC3_* values from <zephyr/bluetooth/audio/lc3.h> have moved to <zephyr/bluetooth/audio/audio.h> and have the LC3 part of their names replaced by a more semantically correct name: e.g. BT_AUDIO_CODEC_LC3_CHAN_COUNT is now BT_AUDIO_CODEC_CAP_TYPE_CHAN_COUNT, BT_AUDIO_CODEC_LC3_FREQ is now BT_AUDIO_CODEC_CAP_TYPE_FREQ, and BT_AUDIO_CODEC_CONFIG_LC3_FREQ is now BT_AUDIO_CODEC_CFG_FREQ, etc. Similarly the enumerations have also been renamed. E.g. bt_audio_codec_config_freq is now bt_audio_codec_cfg_freq, bt_audio_codec_capability_type is now bt_audio_codec_cap_type, bt_audio_codec_config_type is now bt_audio_codec_cfg_type, etc. (GitHub #67024)

  • The ts parameter of bt_bap_stream_send() has been removed. bt_bap_stream_send() now always sends without timestamp. To send with a timestamp, bt_bap_stream_send_ts() can be used.

  • The ts parameter of bt_cap_stream_send() has been removed. bt_cap_stream_send() now always sends without timestamp. To send with a timestamp, bt_cap_stream_send_ts() can be used.


  • The CoAP public API has some minor changes to take into account. The coap_remove_observer() now returns a result if the observer was removed. This change is used by the newly introduced CoAP server subsystem. Also, the request argument for coap_well_known_core_get() is made const. (GitHub #64265)

  • CoAP observer events have moved from a callback function in a CoAP resource to the Network Events subsystem. The CONFIG_COAP_OBSERVER_EVENTS configuration option has been removed. (GitHub #65936)

  • The CoAP public API function coap_pending_init() has changed. The parameter retries is replaced with a pointer to coap_transmission_parameters. This allows to specify retransmission parameters of the confirmable message. It is safe to pass a NULL pointer to use default values. (GitHub #66482)

  • The CoAP public API functions coap_service_send() and coap_resource_send() have changed. An additional parameter pointer to coap_transmission_parameters has been added. It is safe to pass a NULL pointer to use default values. (GitHub #66540)

  • The IGMP multicast library now supports IGMPv3. This results in a minor change to the existing api. The net_ipv4_igmp_join() now takes an additional argument of the type const struct igmp_param *param. This allows IGMPv3 to exclude/include certain groups of addresses. If this functionality is not used or available (when using IGMPv2), you can safely pass a NULL pointer. IGMPv3 can be enabled using the Kconfig CONFIG_NET_IPV4_IGMPV3. (GitHub #65293)

  • The network stack now uses a separate IPv4 TTL (time-to-live) value for multicast packets. Before, the same TTL value was used for unicast and multicast packets. The IPv6 hop limit value is also changed so that unicast and multicast packets can have a different one. (GitHub #65886)

  • The Ethernet phy APIs defined in <zephyr/net/phy.h> are removed from syscall list. The APIs were marked as callable from usermode but in practice this does not work as the device cannot be accessed from usermode thread. This means that the API calls will need to made from supervisor mode thread.

  • The zperf ratio between mbps and kbps, kbps and bps is changed to 1000, instead of 1024, to align with iperf ratios.

  • For network buffer pools maximum allocation size was added to a common structure struct net_buf_data_alloc as a new field max_alloc_size. Similar member data_size of struct net_buf_pool_fixed that was specific only for buffer pools with a fixed size was removed.

Other Subsystems


  • The API to register a callback to provide battery level information to the LoRaWAN stack has been renamed from lorawan_set_battery_level_callback to lorawan_register_battery_level_callback() and the return type is now void. This is more consistent with similar functions for downlink and data rate changed callbacks. (GitHub #65103)


  • MCUmgr applications that make use of serial transports (shell or UART) must now select CONFIG_CRC, this was previously erroneously selected if MCUmgr was enabled, when for non-serial transports it was not needed. (GitHub #64078)




  • A number of userspace related functions have been moved out of the z_ namespace and into the kernel namespace.

    • Z_OOPS to K_OOPS









    • z_user_from_copy to k_usermode_from_copy()

    • z_user_to_copy to k_usermode_to_copy()

    • z_user_string_copy to k_usermode_string_copy()

    • z_user_string_alloc_copy to k_usermode_string_alloc_copy()

    • z_user_alloc_from_copy to k_usermode_alloc_from_copy()

    • z_user_string_nlen to k_usermode_string_nlen()

    • z_dump_object_error to k_object_dump_error()

    • z_object_validate to k_object_validate()

    • z_object_find to k_object_find()

    • z_object_wordlist_foreach to k_object_wordlist_foreach()

    • z_thread_perms_inherit to k_thread_perms_inherit()

    • z_thread_perms_set to k_thread_perms_set()

    • z_thread_perms_clear to k_thread_perms_clear()

    • z_thread_perms_all_clear to k_thread_perms_all_clear()

    • z_object_uninit to k_object_uninit()

    • z_object_recycle to k_object_recycle()

    • z_obj_validation_check to k_object_validation_check()


    • z_object to k_object

    • z_object_init to k_object_init()

    • z_dynamic_object_aligned_create to k_object_create_dynamic_aligned()



  • CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC no longer has a default in the architecture layer. Instead, SoCs or boards will need to define it.

  • Scratch registers ZSR_ALLOCA has been renamed to ZSR_A0SAVE.

  • Renamed files with hyhphens to underscores:

    • xtensa-asm2-context.h to xtensa_asm2_context.h

    • xtensa-asm2-s.h to xtensa_asm2_s.h

  • xtensa_asm2.h has been removed. Use xtensa_asm2_context.h instead for stack frame structs.

  • Renamed functions out of z_ namespace into xtensa_ namespace.

    • z_xtensa_irq_enable to xtensa_irq_enable()

    • z_xtensa_irq_disable to xtensa_irq_disable()

    • z_xtensa_irq_is_enabled to xtensa_irq_is_enabled()