RE: [PATCH net-next v5 4/9] dpll: Support dynamic pin index allocation

[Kubalewski, Arkadiusz]

>From: Ivan Vecera <ivecera@xxxxxxxxxx>
>Sent: Tuesday, February 3, 2026 6:40 PM
>
>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@xxxxxxxxx>

LGTM,
Reviewed-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@xxxxxxxxx>

>Signed-off-by: Ivan Vecera <ivecera@xxxxxxxxxx>
>---
>v2:
>* fixed integer overflow in dpll_pin_idx_free()
>---
> drivers/dpll/dpll_core.c | 48 ++++++++++++++++++++++++++++++++++++++--
> include/linux/dpll.h     |  2 ++
> 2 files changed, 48 insertions(+), 2 deletions(-)
>
>diff --git a/drivers/dpll/dpll_core.c b/drivers/dpll/dpll_core.c
>index b05fe2ba46d91..59081cf2c73ae 100644
>--- a/drivers/dpll/dpll_core.c
>+++ b/drivers/dpll/dpll_core.c
>@@ -10,6 +10,7 @@
>
> #include <linux/device.h>
> #include <linux/err.h>
>+#include <linux/idr.h>
> #include <linux/property.h>
> #include <linux/slab.h>
> #include <linux/string.h>
>@@ -24,6 +25,7 @@ DEFINE_XARRAY_FLAGS(dpll_device_xa, XA_FLAGS_ALLOC);
> DEFINE_XARRAY_FLAGS(dpll_pin_xa, XA_FLAGS_ALLOC);
>
> static RAW_NOTIFIER_HEAD(dpll_notifier_chain);
>+static DEFINE_IDA(dpll_pin_idx_ida);
>
> static u32 dpll_device_xa_id;
> static u32 dpll_pin_xa_id;
>@@ -464,6 +466,36 @@ void dpll_device_unregister(struct dpll_device *dpll,
> }
> EXPORT_SYMBOL_GPL(dpll_device_unregister);
>
>+static int dpll_pin_idx_alloc(u32 *pin_idx)
>+{
>+	int ret;
>+
>+	if (!pin_idx)
>+		return -EINVAL;
>+
>+	/* Alloc unique number from IDA. Number belongs to <0, INT_MAX>
>range */
>+	ret = ida_alloc(&dpll_pin_idx_ida, GFP_KERNEL);
>+	if (ret < 0)
>+		return ret;
>+
>+	/* Map the value to dynamic pin index range <INT_MAX+1, U32_MAX> */
>+	*pin_idx = (u32)ret + INT_MAX + 1;
>+
>+	return 0;
>+}
>+
>+static void dpll_pin_idx_free(u32 pin_idx)
>+{
>+	if (pin_idx <= INT_MAX)
>+		return; /* Not a dynamic pin index */
>+
>+	/* Map the index value from dynamic pin index range to IDA range and
>+	 * free it.
>+	 */
>+	pin_idx -= (u32)INT_MAX + 1;
>+	ida_free(&dpll_pin_idx_ida, pin_idx);
>+}
>+
> static void dpll_pin_prop_free(struct dpll_pin_properties *prop)
> {
> 	kfree(prop->package_label);
>@@ -521,9 +553,18 @@ dpll_pin_alloc(u64 clock_id, u32 pin_idx, struct
>module *module,
> 	struct dpll_pin *pin;
> 	int ret;
>
>+	if (pin_idx == DPLL_PIN_IDX_UNSPEC) {
>+		ret = dpll_pin_idx_alloc(&pin_idx);
>+		if (ret)
>+			return ERR_PTR(ret);
>+	} else if (pin_idx > INT_MAX) {
>+		return ERR_PTR(-EINVAL);
>+	}
> 	pin = kzalloc(sizeof(*pin), GFP_KERNEL);
>-	if (!pin)
>-		return ERR_PTR(-ENOMEM);
>+	if (!pin) {
>+		ret = -ENOMEM;
>+		goto err_pin_alloc;
>+	}
> 	pin->pin_idx = pin_idx;
> 	pin->clock_id = clock_id;
> 	pin->module = module;
>@@ -551,6 +592,8 @@ dpll_pin_alloc(u64 clock_id, u32 pin_idx, struct
>module *module,
> 	dpll_pin_prop_free(&pin->prop);
> err_pin_prop:
> 	kfree(pin);
>+err_pin_alloc:
>+	dpll_pin_idx_free(pin_idx);
> 	return ERR_PTR(ret);
> }
>
>@@ -654,6 +697,7 @@ void dpll_pin_put(struct dpll_pin *pin)
> 		xa_destroy(&pin->ref_sync_pins);
> 		dpll_pin_prop_free(&pin->prop);
> 		fwnode_handle_put(pin->fwnode);
>+		dpll_pin_idx_free(pin->pin_idx);
> 		kfree_rcu(pin, rcu);
> 	}
> 	mutex_unlock(&dpll_lock);
>diff --git a/include/linux/dpll.h b/include/linux/dpll.h
>index 8ed90dfc65f05..8fff048131f1d 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);
>--
>2.52.0