Re: [PATCH v3] drm/i915/kunit: DP Link: Use if statements instead of for loops

On Wed, 12 Aug 2026, Jonathan Cavitt wrote:
> The static functions get_target_config and get_fallback_config in
> intel_dp_link_test.c use for loops to determine if the requested index of
> the config set is in the bounds of the config set entry list.
>
> Reconfigure these functions to use if statements instead, as these for
> loops are only run for a single iteration.
>
> Issue caught by static analysis.
>
> v2: (Michal)
> - Change i <= 0 check to i == 0, as i cannot be negative by assertion
> - Remove unnecessary newlines
>
> v3:
> - Misc. checkpatch fixes
> - Resubmit to exercise target kunit test
>
> Signed-off-by: Jonathan Cavitt <[email protected]>
> Cc: Imre Deak <[email protected]>
> Cc: Michal Grzelak <[email protected]>
> Cc: Jani Nikula <[email protected]>

CI on intel-xe@ doesn't run i915's KUnit tests so it is absent from CI's
report. Nevertheless, here's the report from running it manually on the
series:

[16:06:01] =============== intel_dp_link (17 subtests) ================
[16:06:01] [PASSED] intel_dp_link_caps_test_baseline
[16:06:01] [PASSED] intel_dp_link_caps_test_update_reset
[16:06:01] [PASSED] intel_dp_link_caps_test_update_rates_shrink
[16:06:01] [PASSED] intel_dp_link_caps_test_update_rates_shrink_disable
[16:06:01] [PASSED] intel_dp_link_caps_test_update_rates_expand
[16:06:01] [PASSED] intel_dp_link_caps_test_update_rates_expand_disable
[16:06:01] [PASSED] intel_dp_link_caps_test_update_lanes_shrink
[16:06:01] [PASSED] intel_dp_link_caps_test_update_lanes_shrink_disable
[16:06:01] [PASSED] intel_dp_link_caps_test_update_lanes_expand
[16:06:01] [PASSED] intel_dp_link_caps_test_update_lanes_expand_disable
[16:06:02] [PASSED] intel_dp_link_caps_test_update_params_shrink_random
[16:06:02] [PASSED] intel_dp_link_caps_test_update_params_shrink_disable_random
[16:06:02] [PASSED] intel_dp_link_caps_test_update_params_expand_random
[16:06:02] [PASSED] intel_dp_link_caps_test_update_params_expand_disable_random
[16:06:02] [PASSED] intel_dp_link_test_fallback_for_edp
[16:06:02] [PASSED] intel_dp_link_test_fallback_for_sst
[16:06:02] [PASSED] intel_dp_link_test_fallback_for_mst
[16:06:02] ================== [PASSED] intel_dp_link ==================
[16:06:02] ============================================================
[16:06:02] Testing complete. Ran 17 tests: passed: 17
[16:06:02] Elapsed time: 3.599s total, 0.001s configuring, 2.128s building, 1.440s running

Looks reasonable.

Reviewed-by: MichaÂł Grzelak <[email protected]>
Tested-by: MichaÂł Grzelak <[email protected]>

BR,
MichaÂł

> ---
> .../i915/display/tests/intel_dp_link_test.c   | 34 ++++++++-----------
> 1 file changed, 15 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/tests/intel_dp_link_test.c b/drivers/gpu/drm/i915/display/tests/intel_dp_link_test.c
> index 67c6fe9f1812..608b7a9d60bf 100644
> --- a/drivers/gpu/drm/i915/display/tests/intel_dp_link_test.c
> +++ b/drivers/gpu/drm/i915/display/tests/intel_dp_link_test.c
> @@ -1215,22 +1215,20 @@ static bool get_fallback_config(const struct test_config_table *expected_table,
> 	struct kunit *test = expected_table->test;
> 	const struct link_config_set *config_set =
> 		get_fallback_configs_for_output_type(test, output_type);
> +	const struct intel_dp_link_config *config;
> 	int i;
>
> 	i = lookup_config(config_set, target_config);
> 	KUNIT_ASSERT_GE(test, i, 0);
>
> -	for (i--; i >= 0; i--) {
> -		const struct intel_dp_link_config *config =
> -			&config_set->entries[i];
> +	if (!i)
> +		return false;
>
> -		assert_config_is_supported(expected_table, config);
> -		*fallback_config = *config;
> +	config = &config_set->entries[i - 1];
> +	assert_config_is_supported(expected_table, config);
> +	*fallback_config = *config;
>
> -		return true;
> -	}
> -
> -	return false;
> +	return true;
> }
>
> static bool get_target_config(const struct test_config_table *expected_table,
> @@ -1240,19 +1238,17 @@ static bool get_target_config(const struct test_config_table *expected_table,
> 	struct kunit *test = expected_table->test;
> 	const struct link_config_set *config_set =
> 		get_target_configs_for_output_type(test, output_type);
> -	int i;
> +	const struct intel_dp_link_config *config;
> +	int i = config_set->size - 1;
>
> -	for (i = config_set->size - 1; i >= 0; i--) {
> -		const struct intel_dp_link_config *config =
> -			&config_set->entries[i];
> +	if (i < 0)
> +		return false;
>
> -		assert_config_is_supported(expected_table, config);
> -		*target = *config;
> +	config = &config_set->entries[i];
> +	assert_config_is_supported(expected_table, config);
> +	*target = *config;
>
> -		return true;
> -	}
> -
> -	return false;
> +	return true;
> }
>
> static void test_fallback_seq(struct kunit *test,
> -- 
> 2.53.0
>
>