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Date:   Sat, 25 Mar 2023 09:26:46 +0200
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Subject: Re: [PATCH v5 1/8] drivers: kunit: Generic helpers for test device
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To:     David Gow <davidgow@google.com>
Cc:     Maxime Ripard <maxime@cerno.tech>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Brendan Higgins <brendan.higgins@linux.dev>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
        kunit-dev@googlegroups.com, Stephen Boyd <sboyd@kernel.org>,
        Jonathan Cameron <jic23@kernel.org>, linux-iio@vger.kernel.org
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From:   Matti Vaittinen <mazziesaccount@gmail.com>
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On 3/25/23 06:35, David Gow wrote:
> On Fri, 24 Mar 2023 at 18:17, Matti Vaittinen <mazziesaccount@gmail.com> wrote:
>>
>> On 3/24/23 12:05, Matti Vaittinen wrote:
>>> On 3/24/23 11:52, David Gow wrote:
>>>> On Fri, 24 Mar 2023 at 14:51, Matti Vaittinen
>>>> <mazziesaccount@gmail.com> wrote:
>>>>>
>>>>> On 3/24/23 08:34, David Gow wrote:
>>>>>> On Fri, 24 Mar 2023 at 14:11, Matti Vaittinen
>>>>>> <mazziesaccount@gmail.com> wrote:
>>>
>>>>>> I think that sounds like a good strategy for now, and we can work on a
>>>>>> set of 'generic helpers' which have an associated bus and struct
>>>>>> kunit_device in the meantime. If we can continue to use
>>>>>> root_device_register until those are ready, that'd be very convenient.
>>>>>
>>>>> Would it be a tiny bit more acceptable if we did add a very simple:
>>>>>
>>>>> #define kunit_root_device_register(name) root_device_register(name)
>>>>> #define kunit_root_device_unregister(dev) root_device_unregister(dev)
>>>>>
>>>>> to include/kunit/device.h (or somesuch)
>>>>>
>>>>> This should help us later to at least spot the places where
>>>>> root_device_[un]register() is abused and (potentially mass-)covert them
>>>>> to use the proper helpers when they're available.
>>>>>
>>>>
>>>> Great idea.
>>>>
>>>> The code I've been playing with has the following in
>>>> include/kunit/device.h:
>>>>
>>>> /* Register a new device against a KUnit test. */
>>>> struct device *kunit_device_register(struct kunit *test, const char
>>>> *name);
>>>> /* Unregister a device created by kunit_device_register() early (i.e.,
>>>> before test cleanup). */
>>>> void kunit_device_unregister(struct kunit *test, struct device *dev);
>>>>
>>>> If we used the same names, and just forwarded them to
>>>> root_device_register() and root_device_unregister() for now
>>>> (discarding the struct kunit pointer), then I expect we could just
>>>> swap out the implementation to gain the extra functionality.
>>
>> There's one thing though. If the goal is to do a direct replacement and
>> if automatic device deletion upon test completion / test abort is
>> planned - then it should be there also for these initial wrappers.
>>
> 
> Yeah, that's an excellent point. It's a pretty subtle change in
> behaviour to suddenly introduce that, so changing it behind the scenes
> is probably unwise.
> 
>> If these wrappers don't yet include the automatic device clean-up - then
>> it probably makes more sense to just do the kunit_root_device_* defines
>> because the tests are likely to need removing the explicit device
>> clean-ups when proper APIs are finished.
>>
> 
> I sent out my prototype implementation of this here, which does do the
> automatic cleanup:
> https://lore.kernel.org/linux-kselftest/20230325043104.3761770-1-davidgow@google.com/T/#mf797239a8bce11630875fdf60aab9ed627add1f0
> 
> It's probably overkill to squeeze into your patch series, though,
> given it also adds and uses a whole new kunit_defer() API.

Thanks for letting me know. I did also prepare this commit yesterday:
https://github.com/M-Vaittinen/linux/commit/b784a90f8cc64ff83e802ec818e662fae1d0c264

It does use the existing kunit resources for clean-up. I am not sure if 
it is worth a shot or should I just drop it and use the root-device API 
for now. Any educated opinions on that? :)

Yours,
	-- Matti

-- 
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland

~~ When things go utterly wrong vim users can always type :help! ~~