Hi Marc, thanks for working on mcp251xfd driver that has been pulled into 5.10. I would like to use it with the official rpi-5.4.y branch [1] which currently ships on their Raspberry Pi OS image. The target board is a Raspberry Pi 4 in 32-bit mode which uses bcm2711_defconfig [2] according to their instructions [3]. I copied mcp251xfd from 5.10 and got this error when compiling: =================================================== AR drivers/net/can/spi/mcp251xfd/built-in.a CC [M] drivers/net/can/spi/mcp251xfd/mcp251xfd-core.o drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c: In function ‘mcp251xfd_tx_ring_init_tx_obj’: drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c:314:23: error: request for member ‘value’ in something not a structure or union xfer->cs_change_delay.value = 0; ^ drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c:315:23: error: request for member ‘unit’ in something not a structure or union xfer->cs_change_delay.unit = SPI_DELAY_UNIT_NSECS; ^ drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c: In function ‘mcp251xfd_probe’: drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c:2862:2: error: implicit declaration of function ‘can_rx_offload_add_manual’ [-Werror=implicit-function-declaration] err = can_rx_offload_add_manual(ndev, &priv->offload, ^ cc1: some warnings being treated as errors make[5]: *** [scripts/Makefile.build:266: drivers/net/can/spi/mcp251xfd/mcp251xfd-core.o] Error 1 make[4]: *** [scripts/Makefile.build:500: drivers/net/can/spi/mcp251xfd] Error 2 make[3]: *** [scripts/Makefile.build:500: drivers/net/can/spi] Error 2 make[2]: *** [scripts/Makefile.build:500: drivers/net/can] Error 2 make[1]: *** [scripts/Makefile.build:500: drivers/net] Error 2 make: *** [Makefile:1732: drivers] Error 2 =================================================== I believe this is a result of 329f0dac4cad ("spi: make `cs_change_delay` the first user of the `spi_delay` logic") where integer values `cs_change_delay` and `cs_change_delay_unit` are replaced with `struct spi_delay`. I thought I would ask if you have any advice before I start making incremental changes to get it to compile under 5.4. thank you, drew [1] https://github.com/raspberrypi/linux/blob/rpi-5.4.y/ [2] https://github.com/raspberrypi/linux/blob/rpi-5.4.y/arch/arm/configs/bcm2711_defconfig [3] https://www.raspberrypi.org/documentation/linux/kernel/building.md