[Xenomai-core] Re: Magics of [CAN] message filtering

[Jan Kiszka <jan.kiszka@domain.hid>]

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Oliver Hartkopp wrote:
> When you're touching anything inside your API, have you ever thought to add
> 
> __attribute__ ((aligned(8)))
> 
> to the data[8] element of the struct can_frame?
> 
> This would enable you to make 64 bit compares directly in the data
> section of the can_frame ...
> 
> typedef __u32 canid_t;
> 
> struct can_frame {
>     canid_t can_id;  /* 32 bit CAN_ID + EFF/RTR/ERR flags */
>     __u8    can_dlc; /* data length code: 0 .. 8 */
>     __u8    data[8] __attribute__ ((aligned(8)));
> };

[Swallowing down my well-known opinion on typeof(can_dlc) :)]

Yes, this should be done, already for the more urging sake of
unambiguous layout of the structure across the kernel/user space border.

Jan


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