The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.
Thanks,
Sasha
------------------ original commit in Linus's tree ------------------
From 7af03e688792293ba33149fb8df619a8dff90e80 Mon Sep 17 00:00:00 2001
From: Jani Nikula <jani.nikula@intel.com>
Date: Fri, 8 Mar 2024 18:03:39 +0200
Subject: [PATCH] drm/probe-helper: warn about negative .get_modes()
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
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/50208c866facc33226a3c77b82bb96aeef8ef310.1709913674.git.jani.nikula@intel.com
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 --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
index 19ecb749704be..75f84753f6ee3 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 881b03e4dc288..9ed42469540eb 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);
--
2.43.0