I believe I have encountered two errors with KSDK2.1. I am using it with a K64.
a) In the function FLEXCAN_SetRxFifoConfig in fsl_flexcan.c, the original value of setup_mb is one too low. setup_mb is the number of configured message buffers, and an assert later checks that we have at least one transmit message buffer available. But the initial set is
setup_mb = (base->MCR & CAN_MCR_MAXMB_MASK) >> CAN_MCR_MAXMB_SHIFT;
and this sets the index of the highest available message buffer, which is one lower than the count.
I encountered the problem with a setup of 9 message buffers, and an rx fifo with 8 filters, thus exactly one transmit buffer.
b) in fsl_sim.h, we have the definition
/*!@brief Unique ID. */
typedef struct _sim_uid
uint32_t H; /*!< UIDH. */
uint32_t MH; /*!< UIDMH. */
uint32_t ML; /*!< UIDML. */
uint32_t L; /*!< UIDL. */
But at least for the K64, SIM_UIDH is not defined, but SIM_UIDH_UID is in MK64F12.h