RE: [dpdk-users] [DISCUSSION] code snippet documentation

[Asaf Penso <asafp@oss.nvidia.com>]

>-----Original Message-----
>From: dev <dev-bounces@dpdk.org> On Behalf Of Asaf Penso
>Sent: Sunday, July 25, 2021 7:54 AM
>To: Ferruh Yigit <ferruh.yigit@intel.com>; Ajit Khaparde
><ajit.khaparde@broadcom.com>; NBU-Contact-Thomas Monjalon
><thomas@monjalon.net>
>Cc: users@dpdk.org; dpdk-dev <dev@dpdk.org>; David Marchand
><david.marchand@redhat.com>; Bruce Richardson
><bruce.richardson@intel.com>; Jerin Jacob Kollanukkaran
><jerinj@marvell.com>; Akhil Goyal <gakhil@marvell.com>; Maxime Coquelin
><maxime.coquelin@redhat.com>; Honnappa Nagarahalli
><Honnappa.Nagarahalli@arm.com>; Tu, Lijuan <lijuan.tu@intel.com>
>Subject: Re: [dpdk-dev] [dpdk-users] [DISCUSSION] code snippet
>documentation
>
>Regards,
>Asaf Penso
>
>>-----Original Message-----
>>From: Ferruh Yigit <ferruh.yigit@intel.com>
>>Sent: Friday, July 23, 2021 3:04 PM
>>To: Ajit Khaparde <ajit.khaparde@broadcom.com>; NBU-Contact-Thomas
>>Monjalon <thomas@monjalon.net>
>>Cc: Asaf Penso <asafp@nvidia.com>; users@dpdk.org; dpdk-dev
>><dev@dpdk.org>; David Marchand <david.marchand@redhat.com>; Bruce
>>Richardson <bruce.richardson@intel.com>; Jerin Jacob Kollanukkaran
>><jerinj@marvell.com>; Akhil Goyal <gakhil@marvell.com>; Maxime Coquelin
>><maxime.coquelin@redhat.com>; Honnappa Nagarahalli
>><Honnappa.Nagarahalli@arm.com>; Tu, Lijuan <lijuan.tu@intel.com>
>>Subject: Re: [dpdk-users] [DISCUSSION] code snippet documentation
>>
>>On 7/23/2021 1:02 AM, Ajit Khaparde wrote:
>>> On Thu, Jul 22, 2021 at 1:29 PM Thomas Monjalon
><thomas@monjalon.net>
>>wrote:
>>>>
>>>> 15/07/2021 09:01, Asaf Penso:
>>>>> Hello DPDK community,
>>>>>
>>>>> I would like to bring up a discussion about a way to have code
>>>>> snippets as an
>>example for proper usage.
>>>>> The DPDK tree is filled with great pieces of code that are well
>>>>> documented
>>and maintained in high quality.
>>>>> I feel we are a bit behind when we talk about usage examples.
>>>>>
>>>>> One way, whenever we implement a new feature, is to extend one of
>>>>> the
>>test-* under the "app" folder.
>>>>> This, however, provides means to test but doesn't provide a good
>>>>> usage
>>example.
>>>>>
>>>>> Another way is to check the content of the "example" folder and
>>>>> whenever
>>we have a BIG new feature it seems like a good place.
>>>>> This, however, doesn't provide a good option when we talk about
>>>>> small
>>features.
>>>>> If, for example, we extend rte_flow with an extra action then
>>>>> providing a full-
>>blown example application is somewhat an entry barrier.
>>>>>
>>>>> A third option could be to document it in one of the .rst files we have.
>>>>> Obviously, this requires high maintenance and no option to assure
>>>>> it still
>>compiles.
>>>>>
>>>>> I'd like to propose another approach that will address the main two
>issues:
>>remove the entry barrier and assure compilation.
>>>>> In this approach, inside the "examples" folder we'll create another
>>>>> folder for
>>"snippets".
>>>>> Inside "snippets" we'll have several files per category, for
>>>>> example, rte_flow_snippets.c Each .c file will include a main
>>>>> function that
>>calls the different use cases we want to give as an example.
>>>>> The purpose is not to generate traffic nor read rx/tx packets from
>>>>> the DPDK
>>ports.
>>>>> The purpose is to have a good example that compiles properly.
>>>>>
>>>>> Taking the rte_flow_snippets.c as an example its main function
>>>>> would look
>>like this:
>>>>>
>>>>> int
>>>>> main(int argc, char **argv)
>>>>> {
>>>>>       rte_flow_snippet_match_5tuple_and_drop();
>>>>>       rte_flow_snippet_match_geneve_ope_and_rss();
>>>>>       ...
>>>>>       Return 0;
>>>>> }
>>>>
>>>> I think we need to have a policy or justification about which
>>>> snippet is worth to have.
>>>> My thought is to avoid creating snippets which have no other value
>>>> than showing a function call.
>>>> I think there is a value if the context is not simple.
>>>
>>> I agree. Otherwise it will be cluttered with snippets.
>>>
>>
>>I sometimes use DTS code as sample for an API, that has limited context
>>(which I believe sometimes needed to understand API properly) and of
>>course compiles fine.
>>
>>What about making mandatory to add a test to DTS for each API/feature,
>>that ensures a reasonable sample for the API call.
>>
>>And if the intent is just to provide sample for API call without
>>context, I believe
>>test-* can help on that, it clarifies good & bad input for an API.
>>
>
>Thank you Ferruh, Ajit, and Thomas for your replies.
>I think the more snippets the merrier and we can categorize them for better
>visibility inside the file and among different files.
>Limiting would miss the point of having valid code examples for a variety of
>cases.
>For complex code snippets I fully think that a dedicated test/example app
>should be written but my intention of the snippets is something simpler.
>Reading only documentation is not practical enough and reviewing an
>example app requires too much effort. Snippet is a great tool in between.
>Written DTS test can be an option but I think it is too much overhead if one
>just wants to show how to use a function or an object, without putting effort
>for the "administrative" topics around the snippet.
>
>>>>
>>>>
>>>> Please could you provide a more complex example?
>>>>
>>>>
A good example for a snippet would be the usage of the Flex Item.
On the one hand, it's complex enough, but on the other hand, I don't see an added value of writing all the code for packet acquisition, packet handle, verification etc.
WDYT?