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Date:   Fri, 24 Mar 2023 14:42:17 +0100
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Maxime Ripard <maxime@cerno.tech>
Cc:     Matti Vaittinen <mazziesaccount@gmail.com>,
        Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Brendan Higgins <brendan.higgins@linux.dev>,
        David Gow <davidgow@google.com>,
        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
Subject: Re: [PATCH v5 1/8] drivers: kunit: Generic helpers for test device
 creation
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On Fri, Mar 24, 2023 at 02:02:06PM +0100, Maxime Ripard wrote:
> On Fri, Mar 24, 2023 at 01:43:07PM +0100, Greg Kroah-Hartman wrote:
> > On Fri, Mar 24, 2023 at 01:36:32PM +0100, Maxime Ripard wrote:
> > > On Thu, Mar 23, 2023 at 11:21:58AM +0100, Greg Kroah-Hartman wrote:
> > > > On Thu, Mar 23, 2023 at 11:12:16AM +0100, Maxime Ripard wrote:
> > > > > On Wed, Mar 22, 2023 at 07:57:10PM +0100, Greg Kroah-Hartman wrote:
> > > > > > > > > +/**
> > > > > > > > > + * test_kunit_helper_alloc_device - Allocate a mock device for a KUnit test
> > > > > > > > > + * @test: The test context object
> > > > > > > > > + *
> > > > > > > > > + * This allocates a fake struct &device to create a mock for a KUnit
> > > > > > > > > + * test. The device will also be bound to a fake driver. It will thus be
> > > > > > > > > + * able to leverage the usual infrastructure and most notably the
> > > > > > > > > + * device-managed resources just like a "real" device.
> > > > > > > > 
> > > > > > > > What specific "usual infrastructure" are you wanting to access here?
> > > > > > > > 
> > > > > > > > And again, if you want a fake device, make a virtual one, by just
> > > > > > > > calling device_create().
> > > > > > > > 
> > > > > > > > Or are you wanting to do "more" with that device pointer than
> > > > > > > > device_create() can give you?
> > > > > > > 
> > > > > > > Personally, I was (am) only interested in devm_ unwinding. I guess the
> > > > > > > device_create(), device_add(), device_remove()... (didn't study this
> > > > > > > sequence in details so sorry if there is errors) could've been sufficient
> > > > > > > for me. I haven't looked how much of the code that there is for 'platform
> > > > > > > devices' should be duplicated to support that sequence for testability
> > > > > > > purposes.
> > > > > > 
> > > > > > Any device can access devm_ code, there's no need for it to be a
> > > > > > platform device at all.
> > > > > 
> > > > > Sure but the resources are only released if the device is part of a bus,
> > > > > so it can't be a root_device (or bare device) either
> > > > 
> > > > The resources are not cleaned up when the device is freed no matter if
> > > > it's on a bus or not?  If so, then that's a bug that needs to be fixed,
> > > > and tested :)
> > > 
> > > Please have a look at:
> > > https://lore.kernel.org/linux-kselftest/20230324123157.bbwvfq4gsxnlnfwb@houat/
> > > 
> > > I couldn't get an answer on whether it was considered a bug or not last
> > > time, but as you can see there's a clear difference between a root
> > > device and a platform device that has probed when it comes to resource
> > > cleanup.
> > 
> > Great, testing shows there are bugs!  :)
> 
> I mean, it wasn't clear to me that it was indeed a bug or the intent
> behind devm was that it would only work when probed. Both seemed
> reasonable.
> 
> > That's a great start of a test, how about submitting that in a way that
> > I can test it and we can go from there?
> 
> Ack.
> 
> I guess I'd need to arrange them somewhat differently for it to be
> useful and merge-able.
> 
> How would you prefer them to be submitted, in two different files
> testing both the root devices and platform devices?

root devices are rare, but yes, one for each would be good, thanks!

greg k-h