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In-Reply-To: <Ys50DGXCi5lPaRBB@nanopsycho>
From:   Vikas Gupta <vikas.gupta@broadcom.com>
Date:   Wed, 13 Jul 2022 15:46:03 +0530
Message-ID: <CAHLZf_uw-WtT3ztY=U5M1isxvpvUhPpPXYi2jk2UJxtsWMtBkQ@mail.gmail.com>
Subject: Re: [PATCH net-next v2 1/3] devlink: introduce framework for selftests
To:     Jiri Pirko <jiri@nvidia.com>
Cc:     Jiri Pirko <jiri@resnulli.us>, Jakub Kicinski <kuba@kernel.org>,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        "David S. Miller" <davem@davemloft.net>, dsahern@kernel.org,
        stephen@networkplumber.org, Eric Dumazet <edumazet@google.com>,
        pabeni@redhat.com, ast@kernel.org, leon@kernel.org,
        linux-doc@vger.kernel.org, corbet@lwn.net,
        Michael Chan <michael.chan@broadcom.com>,
        Andrew Gospodarek <andrew.gospodarek@broadcom.com>
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Hi Jiri,

On Wed, Jul 13, 2022 at 12:58 PM Jiri Pirko <jiri@nvidia.com> wrote:
>
> Wed, Jul 13, 2022 at 08:40:50AM CEST, vikas.gupta@broadcom.com wrote:
> >Hi Jiri,
> >
> >On Tue, Jul 12, 2022 at 11:38 PM Jiri Pirko <jiri@resnulli.us> wrote:
> >>
> >> Tue, Jul 12, 2022 at 06:41:49PM CEST, vikas.gupta@broadcom.com wrote:
> >> >Hi Jiri,
> >> >
> >> >On Tue, Jul 12, 2022 at 11:58 AM Jiri Pirko <jiri@nvidia.com> wrote:
> >> >>
> >> >> Tue, Jul 12, 2022 at 08:16:11AM CEST, vikas.gupta@broadcom.com wrote:
> >> >> >Hi Jiri,
> >> >> >
> >> >> >On Mon, Jul 11, 2022 at 6:10 PM Jiri Pirko <jiri@nvidia.com> wrote:
> >> >> >
> >> >> >> Thu, Jul 07, 2022 at 08:29:48PM CEST, vikas.gupta@broadcom.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).
> >
> >For above nesting we can have the attributes defined as below
> >
> >Attribute in  devlink_attr
> >enum devlink_attr {
> >  ....
> >  ....
> >        DEVLINK_SELFTESTS_INFO, /* nested */
> >  ...
> >...
> >}
> >
> >enum devlink_selftests {
> >        DEVLINK_SELFTESTS_SOMETEST0,   /* flag */
> >        DEVLINK_SELFTESTS_SOMETEST1,
> >        DEVLINK_SELFTESTS_SOMETEST2,
> >        ...
> >        ...
> >}
> >
> >enum devlink_selftest_result {
>
> for attrs, have "attr" in the name of the enum and "ATTR" in name of the
> value.
>
> >        DEVLINK_SELFTESTS_RESULT,       /* nested */
> >        DEVLINK_SELFTESTS_TESTNUM,      /* u32  indicating the test
>
> You can have 1 enum, containing both these and the test flags from
> above.
 I think it's better to keep enum devlink_selftests_attr (containing
flags) and devlink_selftest_result_attr separately as it will have an
advantage.
 For example, for show commands the kernel can iterate through and
check with the driver if it supports a particular test.

    for (i = 0; i < DEVLINK_SELFTEST_ATTR_MAX, i++) {
                   if (devlink->ops->selftest_info(devlink, i,
extack)) {  // supports selftest or not
                         nla_put_flag(msg, i);
                }
        }
      Also flags in devlink_selftests_attr can be used as bitwise, if required.
      Let me know what you think.

Thanks,
Vikas

>
>
> >number in devlink_selftests enum */
> >        DEVLINK_SELFTESTS_RESULT_VAL,   /* u8  skip, pass, fail.. */
>
> Put enum name in the comment, instead of list possible values.
>
>
> >        ...some future attrr...
> >
> >}
> >enums in devlink_selftest_result can be put in devlink_attr though.
>
> You can have them separate, I think it is about the time we try to put
> new attrs what does not have potencial to be re-used to a separate enum.
>
>
> >
> >Does this look OK?
> >
> >Thanks,
> >Vikas
> >
> >>
> >>
> >>
> >> >______
> >> >|NEST |
> >> >|_____ | TEST4, RES4|TEST8,RES8|TEST1,RES1|...
> >> >
> >> >Let me know if my understanding is correct.
> >>
> >> [...]
>
>

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