Patch "drm/panel: do not return negative error codes from drm_panel_get_modes()" has been added to the 6.8-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    drm/panel: do not return negative error codes from drm_panel_get_modes()

to the 6.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     drm-panel-do-not-return-negative-error-codes-from-dr.patch
and it can be found in the queue-6.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 8c3c9de9be10dadf371ebd40fdafccf6f4df6e85
Author: Jani Nikula <jani.nikula@xxxxxxxxx>
Date:   Fri Mar 8 18:03:40 2024 +0200

    drm/panel: do not return negative error codes from drm_panel_get_modes()
    
    [ Upstream commit fc4e97726530241d96dd7db72eb65979217422c9 ]
    
    None of the callers of drm_panel_get_modes() expect it to return
    negative error codes. Either they propagate the return value in their
    struct drm_connector_helper_funcs .get_modes() hook (which is also not
    supposed to return negative codes), or add it to other counts leading to
    bogus values.
    
    On the other hand, many of the struct drm_panel_funcs .get_modes() hooks
    do return negative error codes, so handle them gracefully instead of
    propagating further.
    
    Return 0 for no modes, whatever the reason.
    
    Cc: Neil Armstrong <neil.armstrong@xxxxxxxxxx>
    Cc: Jessica Zhang <quic_jesszhan@xxxxxxxxxxx>
    Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
    Cc: stable@xxxxxxxxxxxxxxx
    Reviewed-by: Neil Armstrong <neil.armstrong@xxxxxxxxxx>
    Reviewed-by: Jessica Zhang <quic_jesszhan@xxxxxxxxxxx>
    Acked-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
    Link: https://patchwork.freedesktop.org/patch/msgid/79f559b72d8c493940417304e222a4b04dfa19c4.1709913674.git.jani.nikula@xxxxxxxxx
    Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
index e814020bbcd3b..cfbe020de54e0 100644
--- a/drivers/gpu/drm/drm_panel.c
+++ b/drivers/gpu/drm/drm_panel.c
@@ -274,19 +274,24 @@ EXPORT_SYMBOL(drm_panel_disable);
  * The modes probed from the panel are automatically added to the connector
  * that the panel is attached to.
  *
- * Return: The number of modes available from the panel on success or a
- * negative error code on failure.
+ * Return: The number of modes available from the panel on success, or 0 on
+ * failure (no modes).
  */
 int drm_panel_get_modes(struct drm_panel *panel,
 			struct drm_connector *connector)
 {
 	if (!panel)
-		return -EINVAL;
+		return 0;
 
-	if (panel->funcs && panel->funcs->get_modes)
-		return panel->funcs->get_modes(panel, connector);
+	if (panel->funcs && panel->funcs->get_modes) {
+		int num;
 
-	return -EOPNOTSUPP;
+		num = panel->funcs->get_modes(panel, connector);
+		if (num > 0)
+			return num;
+	}
+
+	return 0;
 }
 EXPORT_SYMBOL(drm_panel_get_modes);