diff mbox series

[1/8] drm/probe-helper: warn about negative .get_modes()

Message ID 50208c866facc33226a3c77b82bb96aeef8ef310.1709913674.git.jani.nikula@intel.com (mailing list archive)
State New, archived
Headers show
Series drm: fix .get_modes() return values | expand

Commit Message

Jani Nikula March 8, 2024, 4:03 p.m. UTC 
The .get_modes() callback is supposed to return the number of modes,
never a negative error code. If a negative value is returned, it'll just
be interpreted as a negative count, and added to previous calculations.

Document the rules, but handle the negative values gracefully with an
error message.

Cc: stable@vger.kernel.org
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/drm_probe_helper.c       | 7 +++++++
 include/drm/drm_modeset_helper_vtables.h | 3 ++-
 2 files changed, 9 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
index 4d60cc810b57..bf2dd1f46b6c 100644
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -422,6 +422,13 @@  static int drm_helper_probe_get_modes(struct drm_connector *connector)
 
 	count = connector_funcs->get_modes(connector);
 
+	/* The .get_modes() callback should not return negative values. */
+	if (count < 0) {
+		drm_err(connector->dev, ".get_modes() returned %pe\n",
+			ERR_PTR(count));
+		count = 0;
+	}
+
 	/*
 	 * Fallback for when DDC probe failed in drm_get_edid() and thus skipped
 	 * override/firmware EDID.
diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
index 881b03e4dc28..9ed42469540e 100644
--- a/include/drm/drm_modeset_helper_vtables.h
+++ b/include/drm/drm_modeset_helper_vtables.h
@@ -898,7 +898,8 @@  struct drm_connector_helper_funcs {
 	 *
 	 * RETURNS:
 	 *
-	 * The number of modes added by calling drm_mode_probed_add().
+	 * The number of modes added by calling drm_mode_probed_add(). Return 0
+	 * on failures (no modes) instead of negative error codes.
 	 */
 	int (*get_modes)(struct drm_connector *connector);