kunit: Setup DMA masks on the kunit device

Commit d393acce7b3f ("drm/tests: Switch to kunit devices") switched the
DRM device creation helpers from an ad-hoc implementation to the new
kunit device creation helpers introduced in commit d03c720e03bd ("kunit:
Add APIs for managing devices").

However, while the DRM helpers were using a platform_device, the kunit
helpers are using a dedicated bus and device type.

That situation creates small differences in the initialisation, and one
of them is that the kunit devices do not have the DMA masks setup. In
turn, this means that we can't do any kind of DMA buffer allocation
anymore, which creates a regression on some (downstream for now) tests.

Let's set up a default DMA mask that should work on any platform to fix
it.

Fixes: d03c720e03bd ("kunit: Add APIs for managing devices")
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

kunit: make kunit_bus_type const

Since commit d492cc2573a0 ("driver core: device.h: make struct
bus_type a const *"), the driver core can properly handle constant
struct bus_type, move the kunit_bus_type variable to be a constant
structure as well, placing it into read-only memory which can not be
modified at runtime.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

kunit: device: Unregister the kunit_bus on shutdown

If KUnit is built as a module, and it's unloaded, the kunit_bus is not
unregistered. This causes an error if it's then re-loaded later, as we
try to re-register the bus.

Unregister the bus and root_device on shutdown, if it looks valid.

In addition, be more specific about the value of kunit_bus_device. It
is:
- a valid struct device* if the kunit_bus initialised correctly.
- an ERR_PTR if it failed to initialise.
- NULL before initialisation and after shutdown.

Fixes: d03c720e03bd ("kunit: Add APIs for managing devices")
Signed-off-by: David Gow <davidgow@google.com>
Reviewed-by: Rae Moar <rmoar@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

kunit: device: Fix a NULL vs IS_ERR() check in init()

The root_device_register() function does not return NULL, it returns
error pointers. Fix the check to match.

Fixes: d03c720e03bd ("kunit: Add APIs for managing devices")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Rae Moar <rmoar@google.com>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

kunit: Fix some comments which were mistakenly kerneldoc

The KUnit device helpers are documented with kerneldoc in their header
file, but also have short comments over their implementation. These were
mistakenly formatted as kerneldoc comments, even though they're not
valid kerneldoc. It shouldn't cause any serious problems -- this file
isn't included in the docs -- but it could be confusing, and causes
warnings.

Remove the extra '*' so that these aren't treated as kerneldoc.

Fixes: d03c720e03bd ("kunit: Add APIs for managing devices")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202312181920.H4EPAH20-lkp@intel.com/
Signed-off-by: David Gow <davidgow@google.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

kunit: Add APIs for managing devices

Tests for drivers often require a struct device to pass to other
functions. While it's possible to create these with
root_device_register(), or to use something like a platform device, this
is both a misuse of those APIs, and can be difficult to clean up after,
for example, a failed assertion.

Add some KUnit-specific functions for registering and unregistering a
struct device:
- kunit_device_register()
- kunit_device_register_with_driver()
- kunit_device_unregister()

These helpers allocate a on a 'kunit' bus which will either probe the
driver passed in (kunit_device_register_with_driver), or will create a
stub driver (kunit_device_register) which is cleaned up on test shutdown.

Devices are automatically unregistered on test shutdown, but can be
manually unregistered earlier with kunit_device_unregister() in order
to, for example, test device release code.

Reviewed-by: Matti Vaittinen <mazziesaccount@gmail.com>
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: David Gow <davidgow@google.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>