dpll: Support dynamic pin index allocation

Allow drivers to register DPLL pins without manually specifying a pin
index.

Currently, drivers must provide a unique pin index when calling
dpll_pin_get(). This works well for hardware-mapped pins but creates
friction for drivers handling virtual pins or those without a strict
hardware indexing scheme.

Introduce DPLL_PIN_IDX_UNSPEC (U32_MAX). When a driver passes this
value as the pin index:
1. The core allocates a unique index using an IDA
2. The allocated index is mapped to a range starting above `INT_MAX`

This separation ensures that dynamically allocated indices never collide
with standard driver-provided hardware indices, which are assumed to be
within the `0` to `INT_MAX` range. The index is automatically freed when
the pin is released in dpll_pin_put().

Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Reviewed-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Link: https://patch.msgid.link/20260203174002.705176-5-ivecera@redhat.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/dpll.h b/include/linux/dpll.h
index 8ed90dfc65f0..8fff048131f1 100644
--- a/include/linux/dpll.h
+++ b/include/linux/dpll.h
@@ -240,6 +240,8 @@ int dpll_device_register(struct dpll_device *dpll, enum dpll_type type,
 void dpll_device_unregister(struct dpll_device *dpll,
 			    const struct dpll_device_ops *ops, void *priv);
 
+#define DPLL_PIN_IDX_UNSPEC	U32_MAX
+
 struct dpll_pin *
 dpll_pin_get(u64 clock_id, u32 dev_driver_id, struct module *module,
 	     const struct dpll_pin_properties *prop);