Re: [dpdk-dev] [PATCH] net: introduce big and little endian types

["Nélio Laranjeiro" <nelio.laranjeiro@6wind.com>]

Hi all,

On Tue, Dec 06, 2016 at 04:34:07PM +0100, Morten Brørup wrote:
> Hi all,
> 
> Being a big fan of strong typing, I really like the concept of
> explicit endian types. Especially if type mismatches can be caught at
> compile time.

+1,

> However, I think it is too late! That train left the station when the
> rest of the world - including libraries and headers that might be
> linked with a DPDK application - decided to use implicit big endian
> types for network protocols, and has been doing so for decades. And,
> with all respect, I don't think the DPDK community has the momentum
> required to change this tradition outside the community.

I don't think, those types can be use from now on to help new API to
expose explicitly the type they are handling.  For older ones, it can
come in a second step, even if there are not so numerous.  Only few of
them touches the network types.

> Furthermore: If not enforced throughout DPDK (and beyond), it might
> confuse more than it helps.

The current situation is more confusing,  nobody at any layer can rely
on a precise information, at each function entry we need to verify if
the callee has already handled the job.  The only solution is to browse
the code to have this information.

Think about any function manipulating network headers (like flow director
or rte_flow) from the API down to the PMD, it may take a lot of time to
know at the end if the data is CPU or network ordered, with those types
it takes less than a second.

Regards,

-- 
Nélio Laranjeiro
6WIND