netdev - Re: [PATCH net-next v2 1/3] devlink: introduce framework for selftests

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Date:   Tue, 12 Jul 2022 20:08:23 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Vikas Gupta <vikas.gupta@...adcom.com>
Cc:     Jiri Pirko <jiri@...dia.com>, Jakub Kicinski <kuba@...nel.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>, dsahern@...nel.org,
        stephen@...workplumber.org, Eric Dumazet <edumazet@...gle.com>,
        pabeni@...hat.com, ast@...nel.org, leon@...nel.org,
        linux-doc@...r.kernel.org, corbet@....net,
        Michael Chan <michael.chan@...adcom.com>,
        Andrew Gospodarek <andrew.gospodarek@...adcom.com>
Subject: Re: [PATCH net-next v2 1/3] devlink: introduce framework for
 selftests

Tue, Jul 12, 2022 at 06:41:49PM CEST, vikas.gupta@...adcom.com wrote:
>Hi Jiri,
>
>On Tue, Jul 12, 2022 at 11:58 AM Jiri Pirko <jiri@...dia.com> wrote:
>>
>> Tue, Jul 12, 2022 at 08:16:11AM CEST, vikas.gupta@...adcom.com wrote:
>> >Hi Jiri,
>> >
>> >On Mon, Jul 11, 2022 at 6:10 PM Jiri Pirko <jiri@...dia.com> wrote:
>> >
>> >> Thu, Jul 07, 2022 at 08:29:48PM CEST, vikas.gupta@...adcom.com wrote:

[...]


>> >> >  * enum devlink_trap_action - Packet trap action.
>> >> >  * @DEVLINK_TRAP_ACTION_DROP: Packet is dropped by the device and a copy
>> >> is not
>> >> >@@ -576,6 +598,10 @@ enum devlink_attr {
>> >> >       DEVLINK_ATTR_LINECARD_TYPE,             /* string */
>> >> >       DEVLINK_ATTR_LINECARD_SUPPORTED_TYPES,  /* nested */
>> >> >
>> >> >+      DEVLINK_ATTR_SELFTESTS_MASK,            /* u32 */
>> >>
>> >> I don't see why this is u32 bitset. Just have one attr per test
>> >> (NLA_FLAG) in a nested attr instead.
>> >>
>> >
>> >As per your suggestion, for an example it should be like as below
>> >
>> >        DEVLINK_ATTR_SELFTESTS,                 /* nested */
>> >
>> >        DEVLINK_ATTR_SELFTESTS_SOMETEST1            /* flag */
>> >
>> >        DEVLINK_ATTR_SELFTESTS_SOMETEST2           /* flag */
>>
>> Yeah, but have the flags in separate enum, no need to pullute the
>> devlink_attr enum by them.
>>
>>
>> >
>> >....    <SOME MORE TESTS>
>> >
>> >.....
>> >
>> >        DEVLINK_ATTR_SLEFTESTS_RESULT_VAL,      /* u8 */
>> >
>> >
>> >
>> > If we have this way then we need to have a mapping (probably a function)
>> >for drivers to tell them what tests need to be executed based on the flags
>> >that are set.
>> > Does this look OK?
>> >  The rationale behind choosing a mask is that we could directly pass the
>> >mask-value to the drivers.
>>
>> If you have separate enum, you can use the attrs as bits internally in
>> kernel. Add a helper that would help the driver to work with it.
>> Pass a struct containing u32 (or u8) not to drivers. Once there are more
>> tests than that, this structure can be easily extended and the helpers
>> changed. This would make this scalable. No need for UAPI change or even
>> internel driver api change.
>
>As per your suggestion, selftest attributes can be declared in separate
>enum as below
>
>enum {
>
>        DEVLINK_SELFTEST_SOMETEST,         /* flag */
>
>        DEVLINK_SELFTEST_SOMETEST1,
>
>        DEVLINK_SELFTEST_SOMETEST2,
>
>....
>
>......
>
>        __DEVLINK_SELFTEST_MAX,
>
>        DEVLINK_SELFTEST_MAX = __DEVLINK_SELFTEST_MAX - 1
>
>};
>Below  examples could be the flow of parameters/data from user to
>kernel and vice-versa
>
>
>Kernel to user for show command . Users can know what all tests are
>supported by the driver. A return from kernel to user.
>______
>|NEST |
>|_____ |TEST1|TEST4|TEST7|...
>
>
>User to kernel to execute test: If user wants to execute test4, test8, test1...
>______
>|NEST |
>|_____ |TEST4|TEST8|TEST1|...
>
>
>Result Kernel to user execute test RES(u8)
>______
>|NEST |
>|_____ |RES4|RES8|RES1|...

Hmm, I think it is not good idea to rely on the order, a netlink library
can perhaps reorder it? Not sure here.

>
>Results are populated in the same order as the user passed the TESTs
>flags. Does the above result format from kernel to user look OK ?
>Else we need to have below way to form a result format, a nest should
>be made for <test_flag,
>result> but since test flags are in different enum other than
>devlink_attr and RES being part of devlink_attr, I believe it's not
>good practice to make the below structure.

Not a structure, no. Have it as another nest (could be the same attr as
the parent nest:

______
|NEST |
|_____ |NEST|       |NEST|       |NEST|
        TEST4,RES4   TEST8,RES8   TEST1, RES1

also, it is flexible to add another attr if needed (like maybe result
message string containing error message? IDK).



>______
>|NEST |
>|_____ | TEST4, RES4|TEST8,RES8|TEST1,RES1|...
>
>Let me know if my understanding is correct.

[...]