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 --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);