Hi, On Thu, Sep 03, 2026 at 05:02:56PM +0800, [email protected] wrote: > From: Shixiong Ou <[email protected]> > > The DRM scheduler KUnit tests currently pass NULL for the dev field in > drm_sched_init_args, which causes a NULL pointer dereference in the > drm_sched_job trace event when it calls dev_name() on sched->dev. > > Use faux_device_create() to create a fake device for the mock scheduler, > so the scheduler always has a valid device pointer. This avoids the > trace event crash without requiring the production code to accept a NULL > device pointer, which conceptually makes no sense for a scheduler. > > An atomic counter is used to generate unique device names, since > multiple mock schedulers can exist simultaneously across different > test suites. > > Signed-off-by: Shixiong Ou <[email protected]> > --- > drivers/gpu/drm/scheduler/tests/mock_scheduler.c | 14 ++++++++++++++ > drivers/gpu/drm/scheduler/tests/sched_tests.h | 2 ++ > 2 files changed, 16 insertions(+) > > diff --git a/drivers/gpu/drm/scheduler/tests/mock_scheduler.c > b/drivers/gpu/drm/scheduler/tests/mock_scheduler.c > index 14403a762335..cd87e405bb1e 100644 > --- a/drivers/gpu/drm/scheduler/tests/mock_scheduler.c > +++ b/drivers/gpu/drm/scheduler/tests/mock_scheduler.c > @@ -1,6 +1,8 @@ > // SPDX-License-Identifier: GPL-2.0 > /* Copyright (c) 2025 Valve Corporation */ > > +#include <linux/device/faux.h> > + > #include "sched_tests.h" > > /* > @@ -10,6 +12,8 @@ > * Test cases are implemented in a separate file. > */ > > +static atomic_t drm_mock_sched_instance = ATOMIC_INIT(0); > + > /** > * drm_mock_sched_entity_new - Create a new mock scheduler entity > * > @@ -296,11 +300,20 @@ struct drm_mock_scheduler *drm_mock_sched_new(struct > kunit *test, long timeout) > .name = "drm-mock-scheduler", > }; > struct drm_mock_scheduler *sched; > + char name[64]; > int ret; > > sched = kunit_kzalloc(test, sizeof(*sched), GFP_KERNEL); > KUNIT_ASSERT_NOT_NULL(test, sched); > > + snprintf(name, sizeof(name), "drm-mock-scheduler-%d", > + atomic_inc_return(&drm_mock_sched_instance)); > + > + sched->faux_dev = faux_device_create(name, NULL, NULL); > + KUNIT_ASSERT_NOT_NULL(test, sched->faux_dev); > + > + args.dev = &sched->faux_dev->dev; > + > ret = drm_sched_init(&sched->base, &args); > KUNIT_ASSERT_EQ(test, ret, 0); > > @@ -323,6 +336,7 @@ struct drm_mock_scheduler *drm_mock_sched_new(struct > kunit *test, long timeout) > void drm_mock_sched_fini(struct drm_mock_scheduler *sched) > { > drm_sched_fini(&sched->base); > + faux_device_destroy(sched->faux_dev); > }
What's wrong with drm_kunit_helper_alloc_device(), or kunit_device_register()? Maxime
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