Re: [PATCH i-g-t 09/11] lib/kms: Pimp the priamry plane swapping

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

On Wed, 17 Dec 2025, Ville Syrjala <ville.syrjala@linux.intel.com> wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> Do the primary plane swap a bit more cleanly with a pair of
> igt_swap()s. And while at it sprinkle some asserts around
> to make sure we didn't screw anything up.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

Subject, *primary

> ---
>  lib/igt_kms.c | 20 ++++++++++++++------
>  1 file changed, 14 insertions(+), 6 deletions(-)
>
> diff --git a/lib/igt_kms.c b/lib/igt_kms.c
> index ef3215332e29..69a430f01e21 100644
> --- a/lib/igt_kms.c
> +++ b/lib/igt_kms.c
> @@ -3025,7 +3025,6 @@ void igt_display_reset_outputs(igt_display_t *display)
>  			igt_plane_t *old_primary = &pipe->planes[0];
>  			igt_plane_t *new_primary =
>  				igt_get_assigned_primary(output, pipe);
> -			int new_primary_index = new_primary->index;
>  
>  			/*
>  			 * If the driver-assigned primary plane isn't at
> @@ -3034,12 +3033,21 @@ void igt_display_reset_outputs(igt_display_t *display)
>  			 *
>  			 * This way, the primary plane is always at index 0.
>  			 */
> -			if (new_primary_index != 0) {
> -				new_primary->index = 0;
> -				old_primary->index = new_primary_index;
> +			if (new_primary->index != 0) {
> +				igt_assert(old_primary != new_primary);
>  
> -				igt_swap(pipe->planes[new_primary_index],
> -					 pipe->planes[0]);
> +				igt_assert_eq(old_primary->index, 0);
> +				igt_assert_neq(new_primary->index, 0);

Nitpick, this is redundant as we're in new_primary->index != 0 branch,
but then again it's symmetric with the post-swap checks. *shrug*.

Anyway I'm glad the asserts are there, because the swaps on *&foo are a
bit hard for the reader.

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

> +
> +				igt_swap(*old_primary, *new_primary);
> +				igt_swap(old_primary->index, new_primary->index);
> +
> +				igt_assert_neq(old_primary->index, 0);
> +				igt_assert_eq(new_primary->index, 0);
> +			} else {
> +				igt_assert(old_primary == new_primary);
> +
> +				igt_assert_eq(old_primary->index, 0);
>  			}
>  		}
>  	}

-- 
Jani Nikula, Intel