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

[Wiles, Keith]

> On Dec 6, 2016, at 10:28 AM, Nélio Laranjeiro <nelio.laranjeiro at 6wind.com> wrote:
> 
> 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.

Still Documentation should handle this problem without code and ABI changes.

> 
> Regards,
> 
> -- 
> Nélio Laranjeiro
> 6WIND

Regards,
Keith