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Message-ID: <7204d8f7-6482-4217-998f-2788d55f4235@intel.com>
Date: Mon, 15 Dec 2025 15:10:39 +0100
From: Przemek Kitszel <przemyslaw.kitszel@...el.com>
To: Ivan Vecera <ivecera@...hat.com>
CC: <netdev@...r.kernel.org>, 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>, Rob Herring
<robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
<conor+dt@...nel.org>, Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
"Arkadiusz Kubalewski" <arkadiusz.kubalewski@...el.com>, Grzegorz Nitka
<grzegorz.nitka@...el.com>, Jiri Pirko <jiri@...nulli.us>, Petr Oros
<poros@...hat.com>, Michal Schmidt <mschmidt@...hat.com>, Prathosh Satish
<Prathosh.Satish@...rochip.com>, Tony Nguyen <anthony.l.nguyen@...el.com>,
Saeed Mahameed <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>, "Tariq
Toukan" <tariqt@...dia.com>, Mark Bloch <mbloch@...dia.com>, Richard Cochran
<richardcochran@...il.com>, Jonathan Lemon <jonathan.lemon@...il.com>, "Simon
Horman" <horms@...nel.org>, Alexander Lobakin <aleksander.lobakin@...el.com>,
Willem de Bruijn <willemb@...gle.com>, Stefan Wahren <wahrenst@....net>,
<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<intel-wired-lan@...ts.osuosl.org>, <linux-rdma@...r.kernel.org>
Subject: Re: [PATCH RFC net-next 06/13] dpll: Support dynamic pin index
allocation
On 12/11/25 20:47, Ivan Vecera wrote:
> 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.
wouldn't it be better to just switch everything to allocated IDs?
>
> 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().
>
> Signed-off-by: Ivan Vecera <ivecera@...hat.com>
> ---
> 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 fecc3d97acf5b..79f60e0de27ac 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;
> @@ -468,6 +470,36 @@ 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 -= 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);
> @@ -526,9 +558,18 @@ 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;
> @@ -557,6 +598,8 @@ 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);
> }
>
> @@ -663,6 +706,7 @@ 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 441afb90d2a29..8aa1df38ce563 100644
> --- a/include/linux/dpll.h
> +++ b/include/linux/dpll.h
> @@ -235,6 +235,8 @@ 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,
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