netdev - [PATCH net-next 09/12] dpll: Prevent duplicate registrations

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Message-ID: <20260108182318.20935-10-ivecera@redhat.com>
Date: Thu,  8 Jan 2026 19:23:15 +0100
From: Ivan Vecera <ivecera@...hat.com>
To: netdev@...r.kernel.org
Cc: Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
	Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>,
	Jiri Pirko <jiri@...nulli.us>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Prathosh Satish <Prathosh.Satish@...rochip.com>,
	Tony Nguyen <anthony.l.nguyen@...el.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Saeed Mahameed <saeedm@...dia.com>,
	Leon Romanovsky <leon@...nel.org>,
	Tariq Toukan <tariqt@...dia.com>,
	Mark Bloch <mbloch@...dia.com>,
	Jonathan Lemon <jonathan.lemon@...il.com>,
	Richard Cochran <richardcochran@...il.com>,
	Alexander Lobakin <aleksander.lobakin@...el.com>,
	devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	intel-wired-lan@...ts.osuosl.org,
	linux-rdma@...r.kernel.org,
	Michal Schmidt <mschmidt@...hat.com>,
	Petr Oros <poros@...hat.com>,
	Grzegorz Nitka <grzegorz.nitka@...el.com>
Subject: [PATCH net-next 09/12] dpll: Prevent duplicate registrations

Modify the internal registration helpers dpll_xa_ref_{dpll,pin}_add()
to reject duplicate registration attempts.

Previously, if a caller attempted to register the same pin multiple
times (with the same ops, priv, and cookie) on the same device, the core
silently increments the reference count and return success. This behavior
is incorrect because if the caller makes these duplicate registrations
then for the first one dpll_pin_registration is allocated and for others
the associated dpll_pin_ref.refcount is incremented. During the first
unregistration the associated dpll_pin_registration is freed and for
others WARN is fired.

Fix this by updating the logic to return `-EEXIST` if a matching
registration is found to enforce a strict "register once" policy.

Signed-off-by: Ivan Vecera <ivecera@...hat.com>
---
 drivers/dpll/dpll_core.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/dpll/dpll_core.c b/drivers/dpll/dpll_core.c
index c1cb9b4a376e7..bc7b75bcf9509 100644
--- a/drivers/dpll/dpll_core.c
+++ b/drivers/dpll/dpll_core.c
@@ -160,10 +160,8 @@ dpll_xa_ref_pin_add(struct xarray *xa_pins, struct dpll_pin *pin,
 		if (ref->pin != pin)
 			continue;
 		reg = dpll_pin_registration_find(ref, ops, priv, cookie);
-		if (reg) {
-			refcount_inc(&ref->refcount);
-			return 0;
-		}
+		if (reg)
+			return -EEXIST;
 		ref_exists = true;
 		break;
 	}
@@ -243,10 +241,8 @@ dpll_xa_ref_dpll_add(struct xarray *xa_dplls, struct dpll_device *dpll,
 		if (ref->dpll != dpll)
 			continue;
 		reg = dpll_pin_registration_find(ref, ops, priv, cookie);
-		if (reg) {
-			refcount_inc(&ref->refcount);
-			return 0;
-		}
+		if (reg)
+			return -EEXIST;
 		ref_exists = true;
 		break;
 	}
-- 
2.52.0