linux-kernel - [PATCH 1/3] drm/display/dp_mst: Don't validate port refs in drm_dp_check_and_send_link

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Message-Id: <20220602201757.30431-2-lyude@redhat.com>
Date:   Thu,  2 Jun 2022 16:17:55 -0400
From:   Lyude Paul <lyude@...hat.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Wayne Lin <Wayne.Lin@....com>,
        Jani Nikula <jani.nikula@...el.com>,
        Bhawanpreet Lakha <Bhawanpreet.Lakha@....com>,
        Rajkumar Subbiah <rsubbia@...eaurora.org>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH 1/3] drm/display/dp_mst: Don't validate port refs in drm_dp_check_and_send_link_address()

Drive-by cleanup, we don't need to validate the port references here as we
already previously went through the effort of refactoring things such that
we're guaranteed to be able to access ->mstb and ->port safely from
drm_dp_check_and_send_link_address(), since the only two places in the
codebase that drop an MST reference in such a way that it would remove it
from the topology are both protected under probe_lock.

Thanks for that, past Lyude!

Signed-off-by: Lyude Paul <lyude@...hat.com>
---
 drivers/gpu/drm/display/drm_dp_mst_topology.c | 22 +++++--------------
 1 file changed, 6 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
index 67b3b9697da7..d84673b3294b 100644
--- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
@@ -2666,24 +2666,14 @@ static int drm_dp_check_and_send_link_address(struct drm_dp_mst_topology_mgr *mg
 	}
 
 	list_for_each_entry(port, &mstb->ports, next) {
-		struct drm_dp_mst_branch *mstb_child = NULL;
-
-		if (port->input || !port->ddps)
+		if (port->input || !port->ddps || !port->mstb)
 			continue;
 
-		if (port->mstb)
-			mstb_child = drm_dp_mst_topology_get_mstb_validated(
-			    mgr, port->mstb);
-
-		if (mstb_child) {
-			ret = drm_dp_check_and_send_link_address(mgr,
-								 mstb_child);
-			drm_dp_mst_topology_put_mstb(mstb_child);
-			if (ret == 1)
-				changed = true;
-			else if (ret < 0)
-				return ret;
-		}
+		ret = drm_dp_check_and_send_link_address(mgr, port->mstb);
+		if (ret == 1)
+			changed = true;
+		else if (ret < 0)
+			return ret;
 	}
 
 	return changed;
-- 
2.35.3