[dpdk-dev] [PATCH v4] ethdev: return named opaque type instead of void pointer

[Ferruh Yigit]

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 at intel.com>
>> Acked-by: Stephen Hemminger <stephen at 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

> 
> Neil
>