Re: [lwip-devel] again... Zero Copy Ethernet interface

[address@hidden]

Alain M. wrote:
> Actualy I have one suggestion that might covver all those and future 
> ones too...
>
> Create a set of fuctions to be implemented in each port, to allocate, 
> release and delete pbufs.
>   
Isn't that the same as what Jonathan suggested with the hooks? Only that 
his implementation uses defines, not functions, which in my opinion is 
better for portability.
> - There should be flags or different functions fot TX/RX
> - there should be provision of the case where a TX pbuf is relased after 
> DMA is completed
> - there should be provision for reentrancy in all this because most will 
> be happening inside IRQs.
> - maybe a few parameters can be available even if they are not used in 
> the refference implementation
>
> The the standard implementation is just what happens today using 
> malloc() and can be a reasonable example to make a first working version...
>   
I think the existing pbuf_alloc() with an additional parameter for TX/RX 
would be enough. We discussed this in the related savannah task already 
and I think the idea was to have PBUF_POOL_RX/_TX pbuf types or 
something similar. Plus the port-hooks of course.

Reentrancy is already provided with SYS_LIGHTWEIGHT_PROT=1. You'd only 
have to make sure your hook implementation also supports it.
> If over time o suitable set of pbuf functions can be found, it would be 
> easy to port. Something like AllocTxPbuf, AllocRxPbuf, FreeTxPbuf... and 
> so on.
>   
Good idea. Although I doubt there is a really lightweight implementation 
to cover all this...? We'll see...

Simon