Re: [PATCH] hw/net/can/sja1000: fix bug for single acceptance filer and standard frame

[Philippe Mathieu-Daudé]

On 14/12/23 11:46, Pavel Pisa wrote:
> From: Pavel Pisa <pisa@cmp.felk.cvut.cz>
>
> A CAN sja1000 standard frame filter mask has been computed and applied
> incorrectly for standard frames when single Acceptance Filter Mode
> (MOD_AFM = 1) has been selected. The problem has not been found
> by Linux kernel testing because it uses dual filter mode (MOD_AFM = 0)
> and leaves falters fully open.
>
> The problem has been noticed by Grant Ramsay when testing with Zephyr
> RTOS which uses single filter mode.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2028
Fixes: 733210e754 ("hw/net/can: SJA1000 chip register level emulation")

> Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>
> Reported-by: Grant Ramsay <gramsay@enphaseenergy.com>
> ---
>   hw/net/can/can_sja1000.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/hw/net/can/can_sja1000.c b/hw/net/can/can_sja1000.c
> index 73201f9139..575df7d2f8 100644
> --- a/hw/net/can/can_sja1000.c
> +++ b/hw/net/can/can_sja1000.c
> @@ -108,7 +108,7 @@ void can_sja_single_filter(struct qemu_can_filter *filter,
>           }
>   
>           filter->can_mask = (uint32_t)amr[0] << 3;
> -        filter->can_mask |= (uint32_t)amr[1] << 5;
> +        filter->can_mask |= (uint32_t)amr[1] >> 5;
>           filter->can_mask = ~filter->can_mask & QEMU_CAN_SFF_MASK;
>           if (!(amr[1] & 0x10)) {
>               filter->can_mask |= QEMU_CAN_RTR_FLAG;