We actually expect this to return a 0 on success, or negative error code on failure. In order to do that, we check whether or not we managed to write the whole GUID and then return 0 if so, otherwise return a negative error code. Also, let's add an error message here so it's a little more obvious when this fails in the middle of a link address probe.
This should fix issues with certain MST hubs seemingly stopping for no reason in the middle of the link address probe process.
Fixes: cb897542c6d2 ("drm/dp_mst: Fix W=1 warnings") Cc: Benjamin Gaignard benjamin.gaignard@st.com Cc: Sean Paul sean@poorly.run Cc: Hans de Goede hdegoede@redhat.com Signed-off-by: Lyude Paul lyude@redhat.com --- drivers/gpu/drm/drm_dp_mst_topology.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index e421c2d13267..b2ec6e8634ed 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -2092,7 +2092,10 @@ static int drm_dp_check_mstb_guid(struct drm_dp_mst_branch *mstb, u8 *guid) } }
- return ret; + if (ret < 16 && ret > 0) + return -EPROTO; + + return ret == 16 ? 0 : ret; }
static void build_mst_prop_path(const struct drm_dp_mst_branch *mstb, @@ -2907,8 +2910,14 @@ static int drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr, drm_dp_dump_link_address(reply);
ret = drm_dp_check_mstb_guid(mstb, reply->guid); - if (ret) + if (ret) { + char buf[64]; + + drm_dp_mst_rad_to_str(mstb->rad, mstb->lct, buf, sizeof(buf)); + DRM_ERROR("GUID check on %s failed: %d\n", + buf, ret); goto out; + }
for (i = 0; i < reply->nports; i++) { port_mask |= BIT(reply->ports[i].port_number);