Re: [PATCH v2 6/8] mbuf: use 2 bytes for port and nb segments

["Morten Brørup" <mb@smartsharesystems.com>]

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Wiles, Keith
> Sent: Tuesday, July 11, 2017 3:26 PM
> To: Morten Brørup
> Cc: Olivier Matz; Wang, Zhihong; Yuanhan Liu; DPDK; Ananyev,
> Konstantin; Richardson, Bruce; Chilikin, Andrey; Jan Blunck;
> nelio.laranjeiro@6wind.com; arybchenko@solarflare.com;
> thomas.monjalon@6wind.com; jerin.jacob@caviumnetworks.com
> Subject: Re: [dpdk-dev] [PATCH v2 6/8] mbuf: use 2 bytes for port and
> nb segments
> 
> 
> On Jul 10, 2017, at 3:15 AM, Morten Brørup
> <mb@smartsharesystems.com<mailto:mb@smartsharesystems.com>> wrote:
> 
> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Olivier Matz
> Sent: Monday, July 10, 2017 10:00 AM
> Subject: Re: [dpdk-dev] [PATCH v2 6/8] mbuf: use 2 bytes for port and
> nb segments
> 
> Hi,
> 
> On Tue, 4 Jul 2017 07:54:23 +0000, "Wang, Zhihong"
> <zhihong.wang@intel.com<mailto:zhihong.wang@intel.com>> wrote:
> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Olivier MATZ
> Sent: Tuesday, April 18, 2017 9:03 PM
> To: Yuanhan Liu
> <yuanhan.liu@linux.intel.com<mailto:yuanhan.liu@linux.intel.com>>
> 
> Hi Yuanhan,
> 
> On Thu, 6 Apr 2017 13:45:23 +0800, Yuanhan Liu
> <yuanhan.liu@linux.intel.com<mailto:yuanhan.liu@linux.intel.com>>
> wrote:
> Hi Olivier,
> 
> On Tue, Apr 04, 2017 at 06:28:05PM +0200, Olivier Matz wrote:
> Change the size of m->port and m->nb_segs to 16 bits.
> 
> But all the ethdev APIs are still using 8 bits. 16 bits won't really
> take effect without updating those APIs. Any plans?
> 
> --yliu
> 
> Yes, there is some work in ethdev, drivers and in example apps to make
> the change effective. I think we could define a specific type for a
> port number, maybe rte_eth_port_num_t. Using this type could be a first
> step (for 17.08) before switching to 16 bits (17.11?).
> 
> I'll do the change and send a rfc.
> 
> Ping ;) Is this still in your plan?
> 
> 
> Sorry, I don't think I will have time to work on this issue in the
> coming weeks. If you plan to do it, I will be happy to help with
> reviews and comments.
> 
> As I said in a previous message, I think a good first step would be to
> introduce a typedef for the port number: rte_eth_port_num_t.
> It can still be uint8_t for now, and can be switched to 16 bits in one
> step when everyone uses this new type.
> 
> Olivier
> 
> I think that DPDK follows the Linux tradition of exposing the variable
> types, as opposed to hiding them behind typedefs. This has the
> unfortunate consequence that when a variable type changes, it has to be
> changed everywhere.
> 
> Introducing a rte_eth_port_num_t will require changing the same files
> at the same locations everywhere, so not even as a temporary solution
> will it be beneficial.
> 
> I would like to see a much smaller typedef name here, we use it
> everywhere.
> rte_port_id_t
> port_id_t
> port_num_t
> portid_t
> 
> I do not see why it needs to be rte_eth or even rte_, if we do not put
> eth in the name then is could be used in crypto or someplace else.
> 
> 
> 
> 
> Med venlig hilsen / kind regards
> - Morten Brørup
> 
> Regards,
> Keith

What I was trying to communicate with my long argument about type definitions was: When the type changed from 8 bit to 16 bit, the type needs to change from uint8_t to uint16_t everywhere too, including in the ethdev APIs.

Don't start breaking coding conventions here by hiding the type of this variable.

Med venlig hilsen / kind regards
- Morten Brørup