Re: [PATCH i-g-t 02/12] tests/amdgpu/amd_multidisplay_modeset: Prepare for returning NULL from igt_crtc_for_pipe()

[Jani Nikula <jani.nikula@intel.com>]

On Wed, 18 Mar 2026, Alex Hung <alex.hung@amd.com> wrote:
> On 3/18/26 12:03, Kamil Konieczny wrote:
>> Hi Jani,
>> On 2026-03-16 at 13:19:04 +0200, Jani Nikula wrote:
>>> AMD should always have enough CRTCs for the test. Assert this is the
>>> case by checking the CRTC is valid.
>>>
>>> This prepares for returning NULL for invalid pipes from
>>> igt_crtc_for_pipe() by ensuring the test logic is sound.
>>>
>> +cc AMD devs
>> Cc: Alex Hung <alex.hung@amd.com>
>> Cc: Hersen Wu <hersenxs.wu@amd.com>
>> Cc: Vitaly Prosyak <vitaly.prosyak@amd.com>
>> 
>>> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>>> ---
>>>   tests/amdgpu/amd_multidisplay_modeset.c | 2 ++
>>>   1 file changed, 2 insertions(+)
>>>
>>> diff --git a/tests/amdgpu/amd_multidisplay_modeset.c b/tests/amdgpu/amd_multidisplay_modeset.c
>>> index 40d1e5d7f42b..ebcfea8ee35f 100644
>>> --- a/tests/amdgpu/amd_multidisplay_modeset.c
>>> +++ b/tests/amdgpu/amd_multidisplay_modeset.c
>>> @@ -327,6 +327,8 @@ static void multiple_display_test(struct data_t *data, enum sub_test test_mode)
>>>   
>>>   			crtc = igt_crtc_for_pipe(display, j);
>>>   
>>> +			igt_assert_f(crtc->valid, "There is no pipe %s\n", kmstest_pipe_name(j));
>>> +
>
> As pointed out by Harry in patch 1, igt_crtc_for_pipe can return NULL 
> when pipe == PIPE_NONE, and it would be a NULL dereference.
>
> How about just checking crtc?
>
>    "igt_assert_f(crtc, "There is no pipe %s\n", kmstest_pipe_name(j));"

Like I said, currently crtc is always != NULL, but might have
!crtc->valid, and the latter is what we want to ensure in this series.

I've sent v2 of the series with more explanation in the cover letter and
commit messages [1].


BR,
Jani.

[1] https://lore.kernel.org/r/cover.1774002591.git.jani.nikula@intel.com


>
>>>   			igt_create_pattern_fb(data->fd, kmode->hdisplay,
>>>   					kmode->vdisplay, DRM_FORMAT_XRGB8888,
>>>   					0, (buf + j));
>>> -- 
>>> 2.47.3
>>>
>

-- 
Jani Nikula, Intel