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From: Thomas Monjalon <thomas@monjalon.net>
To: Neil Horman <nhorman@tuxdriver.com>
Cc: Ferruh Yigit <ferruh.yigit@intel.com>,
	John McNamara <john.mcnamara@intel.com>,
	Marko Kovacevic <marko.kovacevic@intel.com>,
	dev@dpdk.org, Luca Boccassi <bluca@debian.org>,
	Christian Ehrhardt <christian.ehrhardt@canonical.com>
Subject: Re: [dpdk-dev] [RFC] config: remove RTE_NEXT_ABI
Date: Thu, 08 Mar 2018 22:34:14 +0100	[thread overview]
Message-ID: <2251603.sn1Xas34Et@xps> (raw)
In-Reply-To: <20180308194039.GB32578@hmswarspite.think-freely.org>

08/03/2018 20:40, Neil Horman:
> On Thu, Mar 08, 2018 at 05:04:01PM +0100, Thomas Monjalon wrote:
> > 08/03/2018 16:35, Neil Horman:
> > > On Thu, Mar 08, 2018 at 04:17:00PM +0100, Thomas Monjalon wrote:
> > > > 08/03/2018 12:43, Ferruh Yigit:
> > > > > On 3/8/2018 8:05 AM, Thomas Monjalon wrote:
> > > > > > 07/03/2018 18:44, Ferruh Yigit:
> > > > > >> After experimental API process defined do we still need RTE_NEXT_ABI
> > > > > >> config and process which has similar targets?
> > > > > > 
> > > > > > They are different targets.
> > > > > > Experimental API is always enabled but may be avoided by applications.
> > > > > > Next ABI can be used to break ABI without notice and disabled to keep
> > > > > > old ABI compatibility. It is almost never used because it is preferred
> > > > > > to keep ABI compatibility with rte_compat macros, or wait a deprecation
> > > > > > period after notice.
> > > > > 
> > > > > OK, I see.
> > > > > 
> > > > > Shouldn't we disable it by default at least? Otherwise who is not paying
> > > > > attention to this config option will get and ABI/API break.
> > > > 
> > > > Yes I think you are right, it can be disabled by default.
> > > > 
> > > I would agree, there seems to be overlap here, and the experimental tagging can
> > > cover what the NEXT_API flag is meant to do.  It can be removed I think.
> > 
> > It is not NEXT_API but NEXT_ABI.
> Sorry, typo, though I'm sure you got that, since the former doesn't exist,
> right?
> > Why do you think it overlaps experimental API tagging?
> 
> I assert that because the compat lib has macros to map common symbols to version
> specific ones.  That is to say, if you change a data structure, you can setup
> the API calls that use said structure such that version 1 or the symbol maps to
> an internal function that uses the old structure, while version 2 maps to an
> internal function that uses the new symbol
> 
> That is to say, if you're planning on introducing ABI changes, the experimental
> API tagging can be used to implement what the NEXT_ABI macro does.

It is a different usage.
Experimental API tagging is for new functions.
rte_compat is used to avoid breaking the ABI when changing old code.
NEXT_ABI has been used in the past to disable an ABI breakage, which was
not possible to mitigate with rte_compat because impacting too many functions.

I am not saying that I like NEXT_ABI, but it could be useful exceptionnally.

  reply	other threads:[~2018-03-08 21:34 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-07 17:44 Ferruh Yigit
2018-03-07 18:06 ` Luca Boccassi
2018-03-08  8:05 ` Thomas Monjalon
2018-03-08 11:43   ` Ferruh Yigit
2018-03-08 15:17     ` Thomas Monjalon
2018-03-08 15:35       ` Neil Horman
2018-03-08 16:04         ` Thomas Monjalon
2018-03-08 19:40           ` Neil Horman
2018-03-08 21:34             ` Thomas Monjalon [this message]
2018-03-09  0:18               ` Neil Horman
2018-10-04 15:43 ` [dpdk-dev] [PATCH] config: disable RTE_NEXT_ABI by default Ferruh Yigit
2018-10-04 14:49   ` Luca Boccassi
2018-10-04 15:48   ` [dpdk-dev] [PATCH v2] " Ferruh Yigit
2018-10-04 15:10     ` Thomas Monjalon
2018-10-04 15:28       ` Ferruh Yigit
2018-10-04 15:55         ` Thomas Monjalon
2018-10-05  9:13           ` Bruce Richardson
2018-10-05 10:17             ` Ferruh Yigit
2018-10-05 11:30               ` Neil Horman
2018-10-05 12:35                 ` Ferruh Yigit

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