On 28 May 2015 at 14:58, Savolainen, Petri (Nokia - FI/Espoo) < [email protected]> wrote:
> How people think 0 is special or different from e.g. value 1? > A packet of length 1 will require at least one segment. A packet of length 0 does not require any segment from a formal point of view (but an implementation will probably allocate a segment anyway). So implementations might implement zer0 length packets differently. The question is how this can be observed by applications. Preferably not at all. But it seems like implementation specifics are leaking out and some code might expect a certain behavior which is not mandated by the API. We want to avoid this and think we can achieve it by amending the API documentation. I also think the validation suite might need some specific test cases here. > We can change documentation wording, but not add lengthy documentation for > value 0 as a special case (which is not). > > -Petri > > > > -----Original Message----- > > From: ext Zoltan Kiss [mailto:[email protected]] > > Sent: Thursday, May 28, 2015 3:51 PM > > To: Savolainen, Petri (Nokia - FI/Espoo); ext Bill Fischofer > > Cc: [email protected] > > Subject: Re: [lng-odp] [API-NEXT PATCH 2/2] api-next: packet: clarify use > > of 0 len on odp_packet_alloc() > > > > I don't think so. There was a lengthy discussion on the arch meeting how > > should you interpret that, I think that proves it's worth to clarify > > what's the expected behaviour. > > > > On 28/05/15 13:45, Savolainen, Petri (Nokia - FI/Espoo) wrote: > > > I think it should be enough to note that len can be 0. There’s no > > > special handling for value zero. > > > > > > -Petri > > > > > > *From:*ext Bill Fischofer [mailto:[email protected]] > > > *Sent:* Thursday, May 28, 2015 2:48 PM > > > *To:* Savolainen, Petri (Nokia - FI/Espoo) > > > *Cc:* [email protected] > > > *Subject:* Re: [lng-odp] [API-NEXT PATCH 2/2] api-next: packet: clarify > > > use of 0 len on odp_packet_alloc() > > > > > > The purpose of the note was to expand on the case of len = 0. Are you > > > saying this is not needed? The consensus on the Wednesday arch call > was > > > that it was, hence this patch. > > > > > > On Thu, May 28, 2015 at 5:40 AM, Savolainen, Petri (Nokia - FI/Espoo) > > > <[email protected] <mailto:[email protected]>> > wrote: > > > > > > > > > * ... The > > > * packet is initialized with data pointers and lengths set according > > > to the > > > * specified len, ... > > > > > > The current documentation covers functionality also when len is 0. We > > > should minimize @note content over all the APIs, otherwise the actual > > > API spec gets fragmented. API documentation and functionality is the > > > same for len == 0, len == 1, ... In all the cases, implementation > > > decides on packet segmentation in limits of pool parameters. > > > > > > If needed, we could add: > > > > > > @note Zero is a valid 'len' value > > > > > > > > > -Petri > > > > > > > > > > > > > -----Original Message----- > > > > From: lng-odp [mailto:[email protected] > > > <mailto:[email protected]>] On Behalf Of ext > > > > Bill Fischofer > > > > Sent: Wednesday, May 27, 2015 6:51 PM > > > > To: [email protected] <mailto:[email protected]> > > > > Subject: [lng-odp] [API-NEXT PATCH 2/2] api-next: packet: clarify > use > > > of 0 > > > > len on odp_packet_alloc() > > > > > > > > Signed-off-by: Bill Fischofer <[email protected] > > > <mailto:[email protected]>> > > > > --- > > > > include/odp/api/packet.h | 10 ++++++++++ > > > > 1 file changed, 10 insertions(+) > > > > > > > > diff --git a/include/odp/api/packet.h b/include/odp/api/packet.h > > > > index 3a454b5..ea124df 100644 > > > > --- a/include/odp/api/packet.h > > > > +++ b/include/odp/api/packet.h > > > > @@ -73,6 +73,16 @@ extern "C" { > > > > * @note The default headroom and tailroom used for packets is > > specified > > > > by > > > > * the ODP_CONFIG_PACKET_HEADROOM and ODP_CONFIG_PACKET_TAILROOM > > defines > > > > in > > > > * odp_config.h. > > > > + * > > > > + * @note The len parameter sets the initial length of the allocated > > > > packet. > > > > + * If specified as 0, the implementation will allocate a packet of > a > > > > default > > > > + * length chosen by the implementation based on the pool create > > > > parameters > > > > + * and will then set the actual length of the packet to 0. The > > result is > > > > + * the same as if the following sequence had been called by the > > > > application: > > > > + * @code > > > > + * pkt = odp_packet_alloc(pool, default_len); > > > > + * odp_packet_reset(pkt, 0); > > > > + * @endcode > > > > */ > > > > odp_packet_t odp_packet_alloc(odp_pool_t pool, uint32_t len); > > > > > > > > -- > > > > 2.1.0 > > > > > > > > > > > _______________________________________________ > > > > lng-odp mailing list > > > > [email protected] <mailto:[email protected]> > > > > https://lists.linaro.org/mailman/listinfo/lng-odp > > > > > > > > > > > > _______________________________________________ > > > lng-odp mailing list > > > [email protected] > > > https://lists.linaro.org/mailman/listinfo/lng-odp > > > > _______________________________________________ > lng-odp mailing list > [email protected] > https://lists.linaro.org/mailman/listinfo/lng-odp >
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