Re: [PATCH i-g-t v2 05/23] tests/amdgpu/amd_abm: Don't use uninitialized 'pipe'

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

On Sat, 21 Feb 2026, Ville Syrjala <ville.syrjala@linux.intel.com> wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> The for_each_valid_output_on_pipe() loops in amd_abm use an
> uninitialized 'pipe' variable. Not entirely sure what the intention
> was with the change to for_each_valid_output_on_pipe(), but eg.
> set_abm_level() gets called from those loops and it operates on
> data->pipe_id instead of whatever stack garbage pipe the loop
> happens to use. So let's assume the intention was to use the same
> fixed pipe for everything and just pass data->pipe_id to
> for_each_valid_output_on_pipe().

Would be great to get input from the authors, but in any case

Acked-by: Jani Nikula <jani.nikula@intel.com>

>
>  #include "scripts/iterators.cocci"
>
> @@
> iterator name for_each_valid_output_on_pipe;
> expression DISPLAY, OUTPUT;
> identifier PIPE;
> type T;
> @@
> - T PIPE;
> <+... when != PIPE = ...
>   for_each_valid_output_on_pipe(DISPLAY,
> -	PIPE,
> +	data->pipe_id,
> 	OUTPUT)
> 	{...}
> ...+>
>
> Cc: George Zhang <george.zhang@amd.com>
> Cc: Tom Chung <chiahsuan.chung@amd.com>
> Fixes: 1235576931b5 ("tests/amdgpu/amd_abm: Fixed tests to only run on one output per pipe")
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  tests/amdgpu/amd_abm.c | 18 ++++++------------
>  1 file changed, 6 insertions(+), 12 deletions(-)
>
> diff --git a/tests/amdgpu/amd_abm.c b/tests/amdgpu/amd_abm.c
> index 110dd89e3ac2..159f6c7c69e9 100644
> --- a/tests/amdgpu/amd_abm.c
> +++ b/tests/amdgpu/amd_abm.c
> @@ -170,10 +170,9 @@ static void test_fini(data_t *data)
>  {
>  	igt_display_t *display = &data->display;
>  	igt_output_t *output;
> -	enum pipe pipe;
>  
>  	/* Disable ABM before exit test */
> -	for_each_valid_output_on_pipe(&data->display, pipe, output) {
> +	for_each_valid_output_on_pipe(&data->display, data->pipe_id, output) {
>  		if (output->config.connector->connector_type != DRM_MODE_CONNECTOR_eDP)
>  			continue;
>  		set_abm_level(data, output, 0);
> @@ -328,9 +327,8 @@ static void backlight_dpms_cycle(data_t *data)
>  	int max_brightness;
>  	int pwm_1, pwm_2;
>  	igt_output_t *output;
> -	enum pipe pipe;
>  
> -	for_each_valid_output_on_pipe(&data->display, pipe, output) {
> +	for_each_valid_output_on_pipe(&data->display, data->pipe_id, output) {
>  		if (output->config.connector->connector_type != DRM_MODE_CONNECTOR_eDP)
>  			continue;
>  
> @@ -359,10 +357,9 @@ static void backlight_monotonic_basic(data_t *data)
>  	int prev_pwm, pwm;
>  	int brightness_step;
>  	int brightness;
> -	enum pipe pipe;
>  	igt_output_t *output;
>  
> -	for_each_valid_output_on_pipe(&data->display, pipe, output) {
> +	for_each_valid_output_on_pipe(&data->display, data->pipe_id, output) {
>  		if (output->config.connector->connector_type != DRM_MODE_CONNECTOR_eDP)
>  			continue;
>  		ret = backlight_read_max_brightness(&max_brightness);
> @@ -393,10 +390,9 @@ static void backlight_monotonic_abm(data_t *data)
>  	int prev_pwm, pwm;
>  	int brightness_step;
>  	int brightness;
> -	enum pipe pipe;
>  	igt_output_t *output;
>  
> -	for_each_valid_output_on_pipe(&data->display, pipe, output) {
> +	for_each_valid_output_on_pipe(&data->display, data->pipe_id, output) {
>  		if (output->config.connector->connector_type != DRM_MODE_CONNECTOR_eDP)
>  			continue;
>  		ret = backlight_read_max_brightness(&max_brightness);
> @@ -426,10 +422,9 @@ static void abm_enabled(data_t *data)
>  	int ret, i;
>  	int max_brightness;
>  	int pwm, prev_pwm, pwm_without_abm;
> -	enum pipe pipe;
>  	igt_output_t *output;
>  
> -	for_each_valid_output_on_pipe(&data->display, pipe, output) {
> +	for_each_valid_output_on_pipe(&data->display, data->pipe_id, output) {
>  		if (output->config.connector->connector_type != DRM_MODE_CONNECTOR_eDP)
>  			continue;
>  
> @@ -460,10 +455,9 @@ static void abm_gradual(data_t *data)
>  	int convergence_delay = 10;
>  	int prev_pwm, pwm, curr;
>  	int max_brightness;
> -	enum pipe pipe;
>  	igt_output_t *output;
>  
> -	for_each_valid_output_on_pipe(&data->display, pipe, output) {
> +	for_each_valid_output_on_pipe(&data->display, data->pipe_id, output) {
>  		if (output->config.connector->connector_type != DRM_MODE_CONNECTOR_eDP)
>  			continue;

-- 
Jani Nikula, Intel