drm: use drm_warn() in validate_blend_mode_for_alpha_formats()

Commit 860e748bddcc ("drm: ensure blend mode supported if pixel format
with alpha exposed") introduced a WARN() to let driver developers know
that a previously valid behavior should now be changed.

But WARN() should not be used for that, as it's a kernel warning report
mechanism for conditions that are not expected to happen. It also
produces a stack trace. Instead, a simple warning-level log message
should have been used, as drivers were expected to trigger the
condition.

This is causing problems for fuzzers, as they may stop when encountering
a "BUG:" or "WARNING:" in the logs.

Replace WARN() with drm_warn() in this function, avoiding these issues.

Fixes: 860e748bddcc ("drm: ensure blend mode supported if pixel format with alpha exposed")
Signed-off-by: Leandro Ribeiro <leandro.ribeiro@collabora.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Link: https://patch.msgid.link/20260731154232.37020-2-leandro.ribeiro@collabora.com
Signed-off-by: Daniel Stone <daniels@collabora.com>

diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
index 3bcc7bf0900c4317b6d60ae7e15a941867c7ae9f..366f6d8212425eb5114384bad6625c6ae6433cf1 100644 (file)
--- a/drivers/gpu/drm/drm_mode_config.c
+++ b/drivers/gpu/drm/drm_mode_config.c
@@ -869,8 +869,9 @@ static void validate_blend_mode_for_alpha_formats(struct drm_plane *plane)
        for (i = 0; i < plane->format_count; i++) {
                fmt = drm_format_info(plane->format_types[i]);
                if (fmt->has_alpha) {
-                       WARN(1, "[PLANE:%d:%s] pixel format with alpha exposed but blend mode not setup",
-                            plane->base.id, plane->name);
+                       drm_warn(plane->dev,
+                                "[PLANE:%d:%s] pixel format with alpha exposed but blend mode not setup. Please fix.\n",
+                                plane->base.id, plane->name);
                        break;
                }
        }