Re: [PATCH 0/8] clk: Add kunit tests for fixed rate and parent data

[Frank Rowand <frowand.list@gmail.com>]

On 3/2/23 14:18, Rob Herring wrote:
> On Thu, Mar 2, 2023 at 1:44 PM Stephen Boyd <sboyd@kernel.org> wrote:
>>
>> Quoting Rob Herring (2023-03-02 09:13:59)
>>> On Wed, Mar 1, 2023 at 7:38 PM Stephen Boyd <sboyd@kernel.org> wrote:
>>>>
>>>> This patch series adds unit tests for the clk fixed rate basic type and
>>>> the clk registration functions that use struct clk_parent_data. To get
>>>> there, we add support for loading a DTB into the UML kernel that's
>>>> running the unit tests along with probing platform drivers to bind to
>>>> device nodes specified in DT.
>>>>
>>>> With this series, we're able to exercise some of the code in the common
>>>> clk framework that uses devicetree lookups to find parents and the fixed
>>>> rate clk code that scans devicetree directly and creates clks. Please
>>>> review.
>>>>
>>>> I Cced everyone to all the patches so they get the full context. I'm
>>>> hoping I can take the whole pile through the clk tree as they almost all
>>>> depend on each other. In the future I imagine it will be easy to add
>>>> more test nodes to the clk.dtsi file and not need to go across various
>>>> maintainer trees like this series does.
>>>>
>>>> Stephen Boyd (8):
>>>>   dt-bindings: Add linux,kunit binding
>>>>   of: Enable DTB loading on UML for KUnit tests
>>>>   kunit: Add test managed platform_device/driver APIs
>>>>   clk: Add test managed clk provider/consumer APIs
>>>>   dt-bindings: kunit: Add fixed rate clk consumer test
>>>>   clk: Add KUnit tests for clk fixed rate basic type
>>>>   dt-bindings: clk: Add KUnit clk_parent_data test
>>>>   clk: Add KUnit tests for clks registered with struct clk_parent_data
>>>
>>> Good to see bindings for this. I've been meaning to do something about
>>> the DT unittest ones being undocumented, but I hadn't really decided
>>> whether it was worth writing schemas for them. The compatibles at
>>> least show up with 'make dt_compatible_check'. Perhaps we want to just
>>> define some vendor (not 'linux') that's an exception rather than
>>> requiring schemas (actually, that already works for 'foo').
>>
>> Sure. Maybe "kunit" should be the vendor prefix? Or "dtbunit"?
> 
> We'd want to use the same thing on the DT unittests or anything else
> potentially. How about just 'test'?
> 
>>> It's
>>> likely that we want test DTs that fail normal checks and schemas get
>>> in the way of that as we don't have a way to turn off checks.
>>
>> Having the schemas is nice to make sure tests that are expecting some
>> binding are actually getting that. But supporting broken bindings is
>> also important to test any error paths in functions that parse
>> properties. Maybe we keep the schema and have it enforce that incorrect
>> properties are being set?
> 
> I wasn't suggesting throwing them out. More why I hadn't written any I guess.
> 
>> Do we really need to test incorrect bindings? Doesn't the
>> dt_bindings_check catch these problems so we don't have to write DTB
>> verifiers in the kernel?
> 
> Fair enough. Using my frequently stated position against me. :)
> 
> I do have a secret plan to implement (debug) type checks into the
> of_property_* APIs by extracting the type information from schemas
> into C.
> 
> 
>>> We already have GPIO tests in the DT unittests, so why is clocks
>>> different? Or should the GPIO tests be moved out (yes, please!)?
>>
>> Ah I didn't notice the GPIO tests in there. There are i2c tests too,
>> right? All I can say is clks are using kunit, that's the difference ;-)
> 
> Yeah, they should perhaps all move to the subsystems.
> 
>>> What happens when/if the DT unittest is converted to kunit? I think
>>> that would look confusing from the naming. My initial thought is
>>> 'kunit' should be dropped from the naming of a lot of this. Note that
>>> the original kunit submission converted the DT unittests. I would
>>> still like to see that happen. Frank disagreed over what's a unit test
>>> or not, then agreed, then didn't... I don't really care. If there's a
>>> framework to use, then we should use it IMO.
>>
>> Honestly I don't want to get involved in migrating the existing DT
>> unittest code to kunit. I'm aware that it was attempted years ago when
>> kunit was introduced. Maybe if the overlay route works well enough I can
>> completely sidestep introducing any code in drivers/of/ besides some
>> kunit wrappers for this. I'll cross my fingers!
> 
> Yeah, I wasn't expecting you to. I just want to make sure this meshes
> with any future conversion to kunit.
> 
> There's also some plans to always populate the DT root node if not
> present. That may help here. Or not. There's been a few versions
> posted with Frank's in the last week or 2.

As noted in that thread, by code inspection (not actual testing) I
think that the patch series breaks DT unittest for UML.  It should be
a trivial change in the next patch version to fix.

> 
> Rob


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