dpll: Prevent duplicate registrations

From: Ivan Vecera <[email protected]>
Sent: Wednesday, January 21, 2026 2:00 PM

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.

Fixes 9431063ad323 ("dpll: core: Add DPLL framework base functions")

Signed-off-by Ivan Vecera <[email protected]>

---
drivers/dpll/dpll_core.c | 12 ++++--------

1 file changed, 4 insertions(+), 8 deletions(-)

drivers/dpll/dpll_core.c +2 -4

index a461095efd8a..8879a7235156 100644
@@ -83,10 +83,8 @@ 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;

	}

drivers/dpll/dpll_core.c +2 -4

@@ -164,10 +162,8 @@ 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

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.

Fixes 9431063ad323 ("dpll: core: Add DPLL framework base functions")

Signed-off-by Ivan Vecera <[email protected]>

---
  drivers/dpll/dpll_core.c | 12 ++++--------
  1 file changed, 4 insertions(+), 8 deletions(-)