Re: [PATCH v5 1/8] drivers: kunit: Generic helpers for test device creation

[Matti Vaittinen]

On 3/25/23 06:35, David Gow wrote:
> On Fri, 24 Mar 2023 at 18:17, Matti Vaittinen <mazziesaccount@xxxxxxxxx> 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@xxxxxxxxx> wrote:
> > > > > On 3/24/23 08:34, David Gow wrote:
> > > > > > On Fri, 24 Mar 2023 at 14:11, Matti Vaittinen
> > > > > > <mazziesaccount@xxxxxxxxx> 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@xxxxxxxxxx/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

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