The patch below does not apply to the 4.19-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 fc4e97726530241d96dd7db72eb65979217422c9 Mon Sep 17 00:00:00 2001 From: Jani Nikula jani.nikula@intel.com Date: Fri, 8 Mar 2024 18:03:40 +0200 Subject: [PATCH] drm/panel: do not return negative error codes from drm_panel_get_modes()
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@linaro.org Cc: Jessica Zhang quic_jesszhan@quicinc.com Cc: Sam Ravnborg sam@ravnborg.org Cc: stable@vger.kernel.org Reviewed-by: Neil Armstrong neil.armstrong@linaro.org Reviewed-by: Jessica Zhang quic_jesszhan@quicinc.com Acked-by: Thomas Zimmermann tzimmermann@suse.de Link: https://patchwork.freedesktop.org/patch/msgid/79f559b72d8c493940417304e222a4... Signed-off-by: Jani Nikula jani.nikula@intel.com --- drivers/gpu/drm/drm_panel.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-)
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);