Re: [PATCH v4] ethdev: return named opaque type instead of void pointer

[Neil Horman <nhorman@tuxdriver.com>]

On Fri, Mar 09, 2018 at 01:00:35PM +0000, Ferruh Yigit wrote:
> On 3/9/2018 12:36 PM, Neil Horman wrote:
> > On Fri, Mar 09, 2018 at 11:25:31AM +0000, Ferruh Yigit wrote:
> >> "struct rte_eth_rxtx_callback" is defined as internal data structure and
> >> used as named opaque type.
> >>
> >> So the functions that are adding callbacks can return objects in this
> >> type instead of void pointer.
> >>
> >> Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
> >> Acked-by: Stephen Hemminger <stephen@networkplumber.org>
> >> ---
> >> v2:
> >> * keep using struct * in parameters, instead add callback functions
> >> return struct rte_eth_rxtx_callback pointer.
> >>
> >> v4:
> >> * Remove deprecation notice. LIBABIVER already increased in this release
> >> ---
> >>  doc/guides/rel_notes/deprecation.rst |  7 -------
> >>  lib/librte_ether/rte_ethdev.c        |  6 +++---
> >>  lib/librte_ether/rte_ethdev.h        | 13 ++++++++-----
> >>  3 files changed, 11 insertions(+), 15 deletions(-)
> >>
> > This doesn't quite make sense to me.  If rte_eth_rxtx_callback is defined as an
> > internal data structure, then it shouldn't be used as part of the prototype for
> > an exported function, as the structure will then no longer be a internal data
> > structure, but rather part of the public ABI.
> 
> "struct rte_eth_rxtx_callback" is internal data structure. And application
> should not access elements of this structure.
> 
> "struct rte_eth_rxtx_callback;" is defined in the public header, so applications
> can use it as opaque type.
> 
> It is possible that both "add" and "remove" APIs use "void *" and API itself can
> cast it. But the inconsistency was "add" related APIs return "void *" and
> "remove" related APIs require a parameter in "struct rte_eth_rxtx_callback *" type.
> 
> While unifying the usage, "struct rte_eth_rxtx_callback *" preferred against
> "void *", because named opaque type documents intention/usage better.
> 
> Thanks,
> ferruh
> 
I get what you're saying about rte_eth_rxtx_callback being an internals
structure (or its intent is to be an internal structure), but it doesn't seem to
hold up to the header file layout.  rte_eth_rxtx_callback is defined in
rte_ethdev_core.h which according to the makefile, is listed as a symlinked
file, and therefore available for external applications to include.  This
negates the intended opaque nature of the struct.  I think before you do this,
you want to rectify that.

Neil

> > 
> > Neil
> > 
> 
>