Re: [PATCH 3/8] kunit: Add test managed platform_device/driver APIs

Hi Stephen,

On Thu, Mar 09, 2023 at 03:31:15PM -0800, Stephen Boyd wrote:

Quoting Maxime Ripard (2023-03-03 06:35:28)

quoted

On Fri, Mar 03, 2023 at 03:15:31PM +0800, David Gow wrote:

quoted

DRM has a similar thing already (albeit with a root_device, which is
more common with KUnit tests generally):
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/drm/drm_kunit_helpers.h

But that's reasonably drm-specific, so it makes sense that it lives
with DRM stuff. platform_device is a bit more generic.

I'd be very happy to get something from the core to address the same
thing.

I think the main thing we needed that isn't covered by this patch is we
wanted the device to be bound to its driver, so with probe being called
before calling the test (see 57a84a97bbda).

Can you clarify? This patch makes a poor attempt at waiting for the
platform driver to bind, but in reality it may not be bound by the time
the driver register function returns.

The issue was that devm will only clean up the resources if the device
was bound to a driver so we were exhausting resources when running
dozens of test in a sequence.

The way I solved it for vc4 was to create a dumb platform driver with a
waitqueue, and wait for probe to be called.

I think we could make it more generic by allowing a pointer to a probe
function and calling it into our own probe implementation. What do you
think?

Maxime