[NXP HAL] MKV56F24 header incorrectly defines FLEXCAN2, causing FlexCAN build failure

[tbitcs]

Describe the bug

When building for the NXP MKV56F24 SoC (e.g., nxp_kv56f1m0vlx24), the MCUX FlexCAN driver (fsl_flexcan.c) fails to compile because the device header (MKV56F24.h) incorrectly defines FLEXCAN2 as CAN2, even though this SoC only has two FlexCAN instances (CAN0, CAN1).

Incorrect define in MKV56F24.h:

#define FLEXCAN0 CAN0
#define FLEXCAN1 CAN1
#define FLEXCAN2 CAN2  /* <-- Should NOT exist for MKV56F24 */

Error output:

error: 'CAN2' undeclared (first use in this function); did you mean 'CAN0'?
   s_flexcanIsr(FLEXCAN2, s_flexcanHandle[2]);

The SoC feature macros are otherwise correct:

#define FSL_FEATURE_SOC_FLEXCAN_COUNT 2

---

Expected behavior

• FLEXCAN2 should not be defined in MKV56F24.h for a SoC with only 2 FlexCAN instances.
• CAN2 IRQ handlers in fsl_flexcan.c should compile only when:

#if (FSL_FEATURE_SOC_FLEXCAN_COUNT > 2)

---

Root cause

• The MCUXpresso device header (MKV56F24.h) incorrectly defines FLEXCAN2 as CAN2, even though the peripheral does not exist.
• Because FLEXCAN2 is defined, the FlexCAN driver incorrectly assumes CAN2 is present and compiles the extra IRQ handler (CAN_FD2_DriverIRQHandler), which fails.

Correct behavior should be:

#define FLEXCAN0 CAN0
#define FLEXCAN1 CAN1
/* FLEXCAN2 should NOT be defined */

---

Workaround

Add the following to the board’s CMakeLists.txt:

# Workaround: prevent build failure by assigning a dummy value to CAN2.
# This compiles a dead IRQ handler but avoids modifying the SDK.
zephyr_compile_definitions(CAN2=0)

---

Proposed fix

The correct fix must be made upstream in the NXP MCUX SDK:

• Remove or conditionally guard the #define FLEXCAN2 CAN2 in MKV56F24.h.
  For example:

#if (FSL_FEATURE_SOC_FLEXCAN_COUNT > 2)
#define FLEXCAN2 CAN2
#endif

• Optionally, Zephyr could add guards in fsl_flexcan.c as a temporary mitigation:

#if (FSL_FEATURE_SOC_FLEXCAN_COUNT > 2)
void CAN_FD2_DriverIRQHandler(void)
{
    s_flexcanIsr(FLEXCAN2, s_flexcanHandle[2]);
}
#endif

---

Steps to reproduce

1. Build any CAN-enabled application for KV56F24:

   west build -b nxp_kv56f1m0vlx24 samples/subsys/canbus
   

2. Enable CAN:

   CONFIG_CAN=y
   

3. Build fails during compilation of fsl_flexcan.c.

---

Relevant log output

error: 'CAN2' undeclared (first use in this function); did you mean 'CAN0'?
   s_flexcanIsr(FLEXCAN2, s_flexcanHandle[2]);

---

Impact

Annoyance – Minor irritation; no significant impact on functionality, but blocks CAN-enabled builds for KV56F24.

---

Environment

• Zephyr version: 4.1.0 (v4.1.0)
• NXP HAL: hal_nxp as shipped with Zephyr (mirrored MCUX SDK)
• Toolchain: Zephyr SDK 0.17.0 (arm-zephyr-eabi-gcc 12.2.0)
• SoC: MKV56F1M0VLQ24 (KV56F24 series)
• Board: Custom KV56F24 board

---

Additional context

• This issue originates from the NXP MCUXpresso SDK.
• The same incorrect define exists upstream:
  https://github.com/NXPmicro/mcux-sdk (latest KV56F24 header as of 2025‑07‑14).
• Upstream issue tracking this problem:
  [NXP MCUX SDK Issue #237]([BUG] MKV56F24 header incorrectly defines FLEXCAN2, causing build failure in Zephyr 4.1.0 nxp-mcuxpresso/mcux-sdk#237)

Tracking here for Zephyr users since it blocks KV56F24 CAN builds.