zero_copy in RTEMS

Gene Smith gds at
Tue Dec 23 20:27:57 UTC 2008

朱旭峰 wrote, On 12/22/2008 04:59 AM:
> Thanks for your reply, both. 
>         I looked for some information about zerco copy from the 
> internet, and it said that the zero copy is trying to avoid the data 
> copy between the kernel space and the user space, but the memmory space 
> is flat in RTEMS, that is to say there is no difference between kernel 
> space and user space.So I wonder is that possible to realize zero copy 
> in a network interface card driver, and if there is, how to realize it 
> ,is there some source code which I can look up into?I didn't find 
> Coldfire FEC and the EMAC you amentioned in the RTEMS source code.
>         Thanks again.

I think Chris answered your primary question quite well. I will answer 
your question about EMAC. The EMAC controller (I think it was called) 
for IBM ppc405gpr I worked on several years ago experimentally. I know 
my code is not in RTEMS. I originally found the code in NetBSD I think. 
You can probably still find it on their CVS site. Not sure that the 
license is 100% OK with RTEMS (advertising clause and other reasons).

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