[bug report] drm/vkms: Allow to configure multiple CRTCs

[Dan Carpenter]

Hello José Expósito,

Commit 600df32dac40 ("drm/vkms: Allow to configure multiple CRTCs")
from Feb 18, 2025 (linux-next), leads to the following Smatch static
checker warning:

drivers/gpu/drm/vkms/tests/vkms_config_test.c:220 vkms_config_test_get_planes() error: 'plane_cfg1' dereferencing possible ERR_PTR()
drivers/gpu/drm/vkms/tests/vkms_config_test.c:258 vkms_config_test_get_crtcs() error: 'crtc_cfg2' dereferencing possible ERR_PTR()
drivers/gpu/drm/vkms/tests/vkms_config_test.c:300 vkms_config_test_get_encoders() error: 'encoder_cfg2' dereferencing possible ERR_PTR()
drivers/gpu/drm/vkms/tests/vkms_config_test.c:345 vkms_config_test_get_connectors() error: 'connector_cfg2' dereferencing possible ERR_PTR()
drivers/gpu/drm/vkms/tests/vkms_config_test.c:672 vkms_config_test_plane_attach_crtc() error: 'overlay_cfg' dereferencing possible ERR_PTR()
drivers/gpu/drm/vkms/tests/vkms_config_test.c:674 vkms_config_test_plane_attach_crtc() error: 'primary_cfg' dereferencing possible ERR_PTR()
drivers/gpu/drm/vkms/tests/vkms_config_test.c:676 vkms_config_test_plane_attach_crtc() error: 'cursor_cfg' dereferencing possible ERR_PTR()
drivers/gpu/drm/vkms/tests/vkms_config_test.c:685 vkms_config_test_plane_attach_crtc() error: 'crtc_cfg' dereferencing possible ERR_PTR()
drivers/gpu/drm/vkms/tests/vkms_config_test.c:746 vkms_config_test_plane_get_possible_crtcs() error: 'crtc_cfg1' dereferencing possible ERR_PTR()
drivers/gpu/drm/vkms/tests/vkms_config_test.c:746 vkms_config_test_plane_get_possible_crtcs() error: 'plane_cfg1' dereferencing possible ERR_PTR()
drivers/gpu/drm/vkms/tests/vkms_config_test.c:748 vkms_config_test_plane_get_possible_crtcs() error: 'crtc_cfg2' dereferencing possible ERR_PTR()
drivers/gpu/drm/vkms/tests/vkms_config_test.c:810 vkms_config_test_encoder_get_possible_crtcs() error: 'crtc_cfg1' dereferencing possible ERR_PTR()
drivers/gpu/drm/vkms/tests/vkms_config_test.c:810 vkms_config_test_encoder_get_possible_crtcs() error: 'encoder_cfg1' dereferencing possible ERR_PTR()
drivers/gpu/drm/vkms/tests/vkms_config_test.c:812 vkms_config_test_encoder_get_possible_crtcs() error: 'crtc_cfg2' dereferencing possible ERR_PTR()
drivers/gpu/drm/vkms/tests/vkms_config_test.c:876 vkms_config_test_connector_get_possible_encoders() error: 'connector_cfg1' dereferencing possible ERR_PTR()
drivers/gpu/drm/vkms/tests/vkms_config_test.c:876 vkms_config_test_connector_get_possible_encoders() error: 'encoder_cfg1' dereferencing possible ERR_PTR()
drivers/gpu/drm/vkms/tests/vkms_config_test.c:878 vkms_config_test_connector_get_possible_encoders() error: 'encoder_cfg2' dereferencing possible ERR_PTR()

drivers/gpu/drm/vkms/tests/vkms_config_test.c
    231 static void vkms_config_test_get_crtcs(struct kunit *test)
    232 {
    233         struct vkms_config *config;
    234         struct vkms_config_crtc *crtc_cfg;
    235         struct vkms_config_crtc *crtc_cfg1, *crtc_cfg2;
    236 
    237         config = vkms_config_create("test");
    238         KUNIT_ASSERT_NOT_ERR_OR_NULL(test, config);
    239 
    240         KUNIT_ASSERT_EQ(test, vkms_config_get_num_crtcs(config), 0);
    241         vkms_config_for_each_crtc(config, crtc_cfg)
    242                 KUNIT_FAIL(test, "Unexpected CRTC");
    243 
    244         crtc_cfg1 = vkms_config_create_crtc(config);
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This file has no error checking.

I didn't send an email about it at first because this is just test code so
who cares, but I was recently burned by ignoring errors so now I'm going
through a bunch of old warnings to say that, "Hey, if the author ignores the
error checking that's fine, but I'm in the clear."

    245         KUNIT_ASSERT_EQ(test, vkms_config_get_num_crtcs(config), 1);
    246         vkms_config_for_each_crtc(config, crtc_cfg) {
    247                 if (crtc_cfg != crtc_cfg1)
    248                         KUNIT_FAIL(test, "Unexpected CRTC");
    249         }
    250 
    251         crtc_cfg2 = vkms_config_create_crtc(config);
    252         KUNIT_ASSERT_EQ(test, vkms_config_get_num_crtcs(config), 2);
    253         vkms_config_for_each_crtc(config, crtc_cfg) {
    254                 if (crtc_cfg != crtc_cfg1 && crtc_cfg != crtc_cfg2)
    255                         KUNIT_FAIL(test, "Unexpected CRTC");
    256         }
    257 
--> 258         vkms_config_destroy_crtc(config, crtc_cfg2);
    259         KUNIT_ASSERT_EQ(test, vkms_config_get_num_crtcs(config), 1);
    260         vkms_config_for_each_crtc(config, crtc_cfg) {
    261                 if (crtc_cfg != crtc_cfg1)
    262                         KUNIT_FAIL(test, "Unexpected CRTC");
    263         }
    264 
    265         vkms_config_destroy(config);
    266 }

regards,
dan carpenter