[PATCH i-g-t 3/7] lib/igt_kms: Fix max_non_joiner_mode_found

Kunal Joshi
2026-04-01T15:46:07Z

Previously the function, instead of giving the highest possible mode the
connector could support, started the check by looking if the mode was
equal to max_pipe_hdisplay. There may be corner cases where a connector never supports the highest mode our source can
drive (e.g. a 4K mode on a 5K-capable platform).

Fix this by iterating all modes and tracking the best one (highest
hdisplay, then highest clock as a tiebreaker) that does not require a
big joiner, as determined by igt_bigjoiner_possible(). This correctly
handles connectors with any max resolution.

v2: Reword commit message (Suraj)

Fixes: 3830ca6a5068 ("lib/igt_kms: Add support to check joiner mode limit")
Signed-off-by: Kunal Joshi <kunal1.joshi@intel.com>
Reviewed-by: Mohammed Thasleem <mohammed.thasleem@intel.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
---
lib/igt_kms.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/lib/igt_kms.c b/lib/igt_kms.c
index 04b1f3972..dbd419a9b 100644
--- a/lib/igt_kms.c
+++ b/lib/igt_kms.c
@@ -6979,21 +6979,26 @@ bool bigjoiner_mode_found(int drm_fd, drmModeConnector *connector,
* false otherwise.
*/
bool max_non_joiner_mode_found(int drm_fd, drmModeConnector *connector,
- int max_dotclock, drmModeModeInfo *mode)
+ int max_dotclock, drmModeModeInfo *mode)
{
- int max_hdisplay = get_max_pipe_hdisplay(drm_fd);
+ bool found = false;

for (int i = 0; i < connector->count_modes; i++) {
drmModeModeInfo *current_mode = &connector->modes[i];

- if (current_mode->hdisplay == max_hdisplay &&
- current_mode->clock < max_dotclock) {
+ if (igt_bigjoiner_possible(drm_fd, current_mode, max_dotclock))
+ continue;
+
+ if (!found ||
+ current_mode->hdisplay > mode->hdisplay ||
+ (current_mode->hdisplay == mode->hdisplay &&
+ current_mode->clock > mode->clock)) {
*mode = *current_mode;
- return true;
+ found = true;
}
}

- return false;
+ return found;
}

/* TODO: Move these lib functions to the joiner-specific library file
--
2.25.1