Subject: Re: [RFC PATCH v8 03/10] dpll: core: Add DPLL framework base functions

From: Vadim Fedorenko <[email-masked]>
Date: Mon, 17 Jul 2023 20:03:14 +0100

On 10.06.2023 18:38, Jiri Pirko wrote:
> Fri, Jun 09, 2023 at 02:18:46PM CEST, [email-masked] wrote:
>> From: Vadim Fedorenko <[email-masked]>
>>
>> DPLL framework is used to represent and configure DPLL devices
>> in systems. Each device that has DPLL and can configure inputs
>> and outputs can use this framework.
>>
>> Implement core framework functions for further interactions
>> with device drivers implementing dpll subsystem, as well as for
>> interactions of DPLL netlink framework part with the subsystem
>> itself.
>>
>> Co-developed-by: Milena Olech <[email-masked]>
>> Signed-off-by: Milena Olech <[email-masked]>
>> Co-developed-by: Michal Michalik <[email-masked]>
>> Signed-off-by: Michal Michalik <[email-masked]>
>> Signed-off-by: Vadim Fedorenko <[email-masked]>
>> Co-developed-by: Arkadiusz Kubalewski <[email-masked]>
>> Signed-off-by: Arkadiusz Kubalewski <[email-masked]>
>> ---
>> drivers/dpll/dpll_core.c | 953 +++++++++++++++++++++++++++++++++++++++
>> drivers/dpll/dpll_core.h | 104 +++++
> 
> Overall, looks very good! I pinpointed couple of nits below, nothing big.
> General question: Why do you put documentation comment to every static
> function? Does not make any sense to me. Even for non-exported functions
> I think it is overkill. Most of them (if not all) give the reader no
> additional information and only make the code a bit harder to read.
> Care to drop them?
> 
> 
>> 2 files changed, 1057 insertions(+)
>> create mode 100644 drivers/dpll/dpll_core.c
>> create mode 100644 drivers/dpll/dpll_core.h
>>
>> diff --git a/drivers/dpll/dpll_core.c b/drivers/dpll/dpll_core.c
>> new file mode 100644
>> index 000000000000..ee515b7c18be
>> --- /dev/null
>> +++ b/drivers/dpll/dpll_core.c
>> @@ -0,0 +1,953 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + *  dpll_core.c - Generic DPLL Management class support.
> 
> What's "management class support"? Does not sound recognizable.
> 
> 
>> + *
>> + *  Copyright (c) 2023 Meta Platforms, Inc. and affiliates
>> + *  Copyright (c) 2023 Intel Corporation.
>> + */
>> +
>> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>> +
>> +#include <linux/device.h>
>> +#include <linux/err.h>
>> +#include <linux/slab.h>
>> +#include <linux/string.h>
>> +
>> +#include "dpll_core.h"
>> +
>> +DEFINE_MUTEX(dpll_lock);
>> +
>> +DEFINE_XARRAY_FLAGS(dpll_device_xa, XA_FLAGS_ALLOC);
>> +DEFINE_XARRAY_FLAGS(dpll_pin_xa, XA_FLAGS_ALLOC);
>> +
>> +#define ASSERT_DPLL_REGISTERED(d)                                          \
>> +	WARN_ON_ONCE(!xa_get_mark(&dpll_device_xa, (d)->id, DPLL_REGISTERED))
>> +#define ASSERT_DPLL_NOT_REGISTERED(d)                                      \
>> +	WARN_ON_ONCE(xa_get_mark(&dpll_device_xa, (d)->id, DPLL_REGISTERED))
>> +
>> +/**
>> + * dpll_device_get_by_id - find dpll device by it's id
>> + * @id: id of searched dpll
>> + *
>> + * Context: shall be called under a lock (dpll_lock)
>> + * Return:
>> + * * dpll_device struct if found
>> + * * NULL otherwise
>> + */
>> +struct dpll_device *dpll_device_get_by_id(int id)
>> +{
>> +	if (xa_get_mark(&dpll_device_xa, id, DPLL_REGISTERED))
>> +		return xa_load(&dpll_device_xa, id);
>> +
>> +	return NULL;
>> +}
>> +
>> +/**
>> + * dpll_pin_registration_find - find a pin registration record
>> + * @ref: reference between dpll and pin
>> + * @ops: searched pin ops pointer
>> + * @priv: searched pin priv pointer
>> + *
>> + * Search dpll's registered pins for given ops and priv data.
>> + *
>> + * Context: shall be called under a lock (dpll_lock)
>> + * Return:
>> + * * NULL - if pin was not found
>> + * * pointer to `struct dpll_pin_registration` if found
>> + */
>> +static struct dpll_pin_registration *
>> +dpll_pin_registration_find(struct dpll_pin_ref *ref,
>> +			   const struct dpll_pin_ops *ops, void *priv)
>> +{
>> +	struct dpll_pin_registration *reg;
>> +
>> +	list_for_each_entry(reg, &ref->registration_list, list) {
>> +		if (reg->ops == ops && reg->priv == priv)
>> +			return reg;
>> +	}
>> +	return NULL;
>> +}
>> +
>> +/**
>> + * dpll_xa_ref_pin_add - add pin reference to a given xarray
>> + * @xa_pins: dpll_pin_ref xarray holding pins
>> + * @pin: pin being added
>> + * @ops: ops for a pin
>> + * @priv: pointer to private data of owner
>> + *
>> + * Allocate and create reference of a pin and enlist a registration
>> + * structure storing ops and priv pointers of a caller registant.
>> + *
>> + * Context: shall be called under a lock (dpll_lock)
>> + * Return:
>> + * * 0 on success
>> + * * -ENOMEM on failed allocation
>> + */
>> +static int
>> +dpll_xa_ref_pin_add(struct xarray *xa_pins, struct dpll_pin *pin,
>> +		    const struct dpll_pin_ops *ops, void *priv)
>> +{
>> +	struct dpll_pin_registration *reg;
>> +	struct dpll_pin_ref *ref;
>> +	bool ref_exists = false;
>> +	unsigned long i;
>> +	int ret;
>> +
>> +	xa_for_each(xa_pins, i, ref) {
>> +		if (ref->pin != pin)
>> +			continue;
>> +		reg = dpll_pin_registration_find(ref, ops, priv);
>> +		if (reg) {
>> +			refcount_inc(&ref->refcount);
>> +			return 0;
>> +		}
>> +		ref_exists = true;
>> +		break;
>> +	}
>> +
>> +	if (!ref_exists) {
>> +		ref = kzalloc(sizeof(*ref), GFP_KERNEL);
>> +		if (!ref)
>> +			return -ENOMEM;
>> +		ref->pin = pin;
>> +		INIT_LIST_HEAD(&ref->registration_list);
>> +		ret = xa_insert(xa_pins, pin->pin_idx, ref, GFP_KERNEL);
>> +		if (ret) {
>> +			kfree(ref);
>> +			return ret;
>> +		}
>> +		refcount_set(&ref->refcount, 1);
>> +	}
>> +
>> +	reg = kzalloc(sizeof(*reg), GFP_KERNEL);
>> +	if (!reg) {
>> +		if (!ref_exists)
>> +			kfree(ref);
>> +		return -ENOMEM;
>> +	}
>> +	reg->ops = ops;
>> +	reg->priv = priv;
>> +	if (ref_exists)
> 
> If you set refcount to 0 couple of lines above, you can drop the check
> here.
> 

   This is impossible. You cannot increment on zero refcount, it's treated as 
use-after-free. I'll think about re-arrange the code a bit to avoid such 
contructions of possible.

> 
>> +		refcount_inc(&ref->refcount);
>> +	list_add_tail(&reg->list, &ref->registration_list);
>> +
>> +	return 0;
>> +}
>> +
>> +/**
>> + * dpll_xa_ref_pin_del - remove reference of a pin from xarray
>> + * @xa_pins: dpll_pin_ref xarray holding pins
>> + * @pin: pointer to a pin being removed
>> + * @ops: pointer to ops of pin being removed
>> + * @priv: pointer to private data of registerer who invoked pin removal
>> + *
>> + * Decrement refcount of existing pin reference on given xarray.
>> + * If all registrations are lifted delete the reference and free its memory.
>> + *
>> + * Context: shall be called under a lock (dpll_lock)
>> + * Return:
>> + * * 0 on success
>> + * * -EINVAL if reference to a pin was not found
>> + */
>> +static int dpll_xa_ref_pin_del(struct xarray *xa_pins, struct dpll_pin *pin,
>> +			       const struct dpll_pin_ops *ops, void *priv)
>> +{
>> +	struct dpll_pin_registration *reg;
>> +	struct dpll_pin_ref *ref;
>> +	unsigned long i;
>> +
>> +	xa_for_each(xa_pins, i, ref) {
>> +		if (ref->pin != pin)
>> +			continue;
>> +		reg = dpll_pin_registration_find(ref, ops, priv);
>> +		if (WARN_ON(!reg))
>> +			return -EINVAL;
>> +		if (refcount_dec_and_test(&ref->refcount)) {
>> +			list_del(&reg->list);
>> +			kfree(reg);
>> +			xa_erase(xa_pins, i);
>> +			WARN_ON(!list_empty(&ref->registration_list));
>> +			kfree(ref);
>> +		}
>> +		return 0;
>> +	}
>> +
>> +	return -EINVAL;
>> +}
>> +
>> +/**
>> + * dpll_xa_ref_dpll_add - add dpll reference to a given xarray
>> + * @xa_dplls: dpll_pin_ref xarray holding dplls
>> + * @dpll: dpll being added
>> + * @ops: pin-reference ops for a dpll
>> + * @priv: pointer to private data of owner
>> + *
>> + * Allocate and create reference of a dpll-pin ops or increase refcount
>> + * on existing dpll reference on given xarray.
>> + *
>> + * Context: shall be called under a lock (dpll_lock)
>> + * Return:
>> + * * 0 on success
>> + * * -ENOMEM on failed allocation
>> + */
>> +static int
>> +dpll_xa_ref_dpll_add(struct xarray *xa_dplls, struct dpll_device *dpll,
>> +		     const struct dpll_pin_ops *ops, void *priv)
>> +{
>> +	struct dpll_pin_registration *reg;
>> +	struct dpll_pin_ref *ref;
>> +	bool ref_exists = false;
>> +	unsigned long i;
>> +	int ret;
>> +
>> +	xa_for_each(xa_dplls, i, ref) {
>> +		if (ref->dpll != dpll)
>> +			continue;
>> +		reg = dpll_pin_registration_find(ref, ops, priv);
>> +		if (reg) {
>> +			refcount_inc(&ref->refcount);
>> +			return 0;
>> +		}
>> +		ref_exists = true;
>> +		break;
>> +	}
>> +
>> +	if (!ref_exists) {
>> +		ref = kzalloc(sizeof(*ref), GFP_KERNEL);
>> +		if (!ref)
>> +			return -ENOMEM;
>> +		ref->dpll = dpll;
>> +		INIT_LIST_HEAD(&ref->registration_list);
>> +		ret = xa_insert(xa_dplls, dpll->device_idx, ref, GFP_KERNEL);
>> +		if (ret) {
>> +			kfree(ref);
>> +			return ret;
>> +		}
>> +		refcount_set(&ref->refcount, 1);
>> +	}
>> +
>> +	reg = kzalloc(sizeof(*reg), GFP_KERNEL);
>> +	if (!reg) {
>> +		if (!ref_exists)
>> +			kfree(ref);
>> +		return -ENOMEM;
>> +	}
>> +	reg->ops = ops;
>> +	reg->priv = priv;
>> +	if (ref_exists)
> 
> If you set refcount to 0 couple of lines above, you can drop the check
> here.
> 
> 
>> +		refcount_inc(&ref->refcount);
>> +	list_add_tail(&reg->list, &ref->registration_list);
>> +
>> +	return 0;
>> +}
>> +
>> +/**
>> + * dpll_xa_ref_dpll_del - remove reference of a dpll from xarray
>> + * @xa_dplls: dpll_pin_ref xarray holding dplls
>> + * @dpll: pointer to a dpll to remove
>> + * @ops: pointer to ops of dpll being removed
>> + * @priv: pointer to private data of registerer who invoked dpll removal
>> + *
>> + * Decrement refcount of existing dpll reference on given xarray.
>> + * If all references are dropped, delete the reference and free its memory.
>> + *
>> + * Context: shall be called under a lock (dpll_lock)
>> + */
>> +static void
>> +dpll_xa_ref_dpll_del(struct xarray *xa_dplls, struct dpll_device *dpll,
>> +		     const struct dpll_pin_ops *ops, void *priv)
>> +{
>> +	struct dpll_pin_registration *reg;
>> +	struct dpll_pin_ref *ref;
>> +	unsigned long i;
>> +
>> +	xa_for_each(xa_dplls, i, ref) {
>> +		if (ref->dpll != dpll)
>> +			continue;
>> +		reg = dpll_pin_registration_find(ref, ops, priv);
>> +		if (WARN_ON(!reg))
>> +			return;
>> +		if (refcount_dec_and_test(&ref->refcount)) {
>> +			list_del(&reg->list);
>> +			kfree(reg);
>> +			xa_erase(xa_dplls, i);
>> +			WARN_ON(!list_empty(&ref->registration_list));
>> +			kfree(ref);
>> +		}
>> +		return;
>> +	}
>> +}
>> +
>> +/**
>> + * dpll_xa_ref_dpll_find - find dpll reference on xarray
>> + * @xa_refs: dpll_pin_ref xarray holding dpll references
>> + * @dpll: pointer to a dpll being searched
>> + *
>> + * Search for dpll-pin ops reference struct of a given dpll on given xarray.
>> + *
>> + * Context: shall be called under a lock (dpll_lock)
>> + * Return:
>> + * * pin reference struct pointer on success
>> + * * NULL - reference to a pin was not found
>> + */
>> +struct dpll_pin_ref *
>> +dpll_xa_ref_dpll_find(struct xarray *xa_refs, const struct dpll_device *dpll)
>> +{
>> +	struct dpll_pin_ref *ref;
>> +	unsigned long i;
>> +
>> +	xa_for_each(xa_refs, i, ref) {
>> +		if (ref->dpll == dpll)
>> +			return ref;
>> +	}
>> +
>> +	return NULL;
>> +}
>> +
>> +/**
>> + * dpll_xa_ref_dpll_first - find first record of given xarray
>> + * @xa_refs: xarray
>> + *
>> + * Context: shall be called under a lock (dpll_lock)
>> + * Return: first element on given xaaray
>> + */
>> +struct dpll_pin_ref *dpll_xa_ref_dpll_first(struct xarray *xa_refs)
>> +{
>> +	struct dpll_pin_ref *ref;
>> +	unsigned long i = 0;
>> +
>> +	ref = xa_find(xa_refs, &i, ULONG_MAX, XA_PRESENT);
>> +	WARN_ON(!ref);
>> +	return ref;
>> +}
>> +
>> +/**
>> + * dpll_device_alloc - allocate the memory for dpll device
>> + * @clock_id: clock_id of creator
>> + * @device_idx: id given by dev driver
>> + * @module: reference to registering module
>> + *
>> + * Allocates memory and initialize dpll device, hold its reference on global
>> + * xarray.
>> + *
>> + * Context: shall be called under a lock (dpll_lock)
>> + * Return:
>> + * * valid dpll_device struct pointer if succeeded
>> + * * ERR_PTR(-ENOMEM) - failed memory allocation
>> + * * ERR_PTR(X) - failed allocation on dpll's xa
>> + */
>> +static struct dpll_device *
>> +dpll_device_alloc(const u64 clock_id, u32 device_idx, struct module *module)
>> +{
>> +	struct dpll_device *dpll;
>> +	int ret;
>> +
>> +	dpll = kzalloc(sizeof(*dpll), GFP_KERNEL);
>> +	if (!dpll)
>> +		return ERR_PTR(-ENOMEM);
>> +	refcount_set(&dpll->refcount, 1);
>> +	INIT_LIST_HEAD(&dpll->registration_list);
>> +	dpll->device_idx = device_idx;
>> +	dpll->clock_id = clock_id;
>> +	dpll->module = module;
>> +	ret = xa_alloc(&dpll_device_xa, &dpll->id, dpll, xa_limit_16b,
>> +		       GFP_KERNEL);
>> +	if (ret) {
>> +		kfree(dpll);
>> +		return ERR_PTR(ret);
>> +	}
>> +	xa_init_flags(&dpll->pin_refs, XA_FLAGS_ALLOC);
>> +
>> +	return dpll;
>> +}
>> +
>> +/**
>> + * dpll_device_get - find existing or create new dpll device
>> + * @clock_id: clock_id of creator
>> + * @device_idx: idx given by device driver
>> + * @module: reference to registering module
>> + *
>> + * Get existing object of a dpll device, unique for given arguments.
>> + * Create new if doesn't exist yet.
>> + *
>> + * Context: Acquires a lock (dpll_lock)
>> + * Return:
>> + * * valid dpll_device struct pointer if succeeded
>> + * * ERR_PTR(-ENOMEM) - failed memory allocation
>> + * * ERR_PTR(X) - failed allocation on dpll's xa
>> + */
>> +struct dpll_device *
>> +dpll_device_get(u64 clock_id, u32 device_idx, struct module *module)
>> +{
>> +	struct dpll_device *dpll, *ret = NULL;
>> +	unsigned long index;
>> +
>> +	mutex_lock(&dpll_lock);
>> +	xa_for_each(&dpll_device_xa, index, dpll) {
>> +		if (dpll->clock_id == clock_id &&
>> +		    dpll->device_idx == device_idx &&
>> +		    dpll->module == module) {
>> +			ret = dpll;
>> +			refcount_inc(&ret->refcount);
>> +			break;
>> +		}
>> +	}
>> +	if (!ret)
>> +		ret = dpll_device_alloc(clock_id, device_idx, module);
>> +	mutex_unlock(&dpll_lock);
>> +
>> +	return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(dpll_device_get);
>> +
>> +/**
>> + * dpll_device_put - decrease the refcount and free memory if possible
>> + * @dpll: dpll_device struct pointer
>> + *
>> + * Context: Acquires a lock (dpll_lock)
>> + * Drop reference for a dpll device, if all references are gone, delete
>> + * dpll device object.
>> + */
>> +void dpll_device_put(struct dpll_device *dpll)
>> +{
>> +	if (!dpll)
> 
> Drop this check and rely on a basic driver sanity. I'm pretty sure I
> asked you to drop checks like this during the last version review.
> 
> 
>> +		return;
>> +	mutex_lock(&dpll_lock);
>> +	if (refcount_dec_and_test(&dpll->refcount)) {
>> +		ASSERT_DPLL_NOT_REGISTERED(dpll);
>> +		WARN_ON_ONCE(!xa_empty(&dpll->pin_refs));
>> +		xa_destroy(&dpll->pin_refs);
>> +		xa_erase(&dpll_device_xa, dpll->id);
>> +		WARN_ON(!list_empty(&dpll->registration_list));
>> +		kfree(dpll);
>> +	}
>> +	mutex_unlock(&dpll_lock);
>> +}
>> +EXPORT_SYMBOL_GPL(dpll_device_put);
>> +
>> +static struct dpll_device_registration *
>> +dpll_device_registration_find(struct dpll_device *dpll,
>> +			      const struct dpll_device_ops *ops, void *priv)
>> +{
>> +	struct dpll_device_registration *reg;
>> +
>> +	list_for_each_entry(reg, &dpll->registration_list, list) {
>> +		if (reg->ops == ops && reg->priv == priv)
>> +			return reg;
>> +	}
>> +	return NULL;
>> +}
>> +
>> +/**
>> + * dpll_device_register - register the dpll device in the subsystem
>> + * @dpll: pointer to a dpll
>> + * @type: type of a dpll
>> + * @ops: ops for a dpll device
>> + * @priv: pointer to private information of owner
>> + *
>> + * Make dpll device available for user space.
>> + *
>> + * Context: Acquires a lock (dpll_lock)
>> + * Return:
>> + * * 0 on success
>> + * * -EINVAL on failure due to wrong arguments provided
>> + * * -EEXIST if device was already registered
>> + */
>> +int dpll_device_register(struct dpll_device *dpll, enum dpll_type type,
>> +			 const struct dpll_device_ops *ops, void *priv)
>> +{
>> +	struct dpll_device_registration *reg;
>> +	bool first_registration = false;
>> +
>> +	if (WARN_ON(!ops))
>> +		return -EINVAL;
>> +	if (WARN_ON(type < DPLL_TYPE_PPS || type > DPLL_TYPE_MAX))
>> +		return -EINVAL;
>> +
>> +	mutex_lock(&dpll_lock);
>> +	reg = dpll_device_registration_find(dpll, ops, priv);
>> +	if (reg) {
>> +		mutex_unlock(&dpll_lock);
>> +		return -EEXIST;
>> +	}
>> +
>> +	reg = kzalloc(sizeof(*reg), GFP_KERNEL);
>> +	if (!reg) {
>> +		mutex_unlock(&dpll_lock);
>> +		return -EEXIST;
> 
> -ENOMEM;
> 
> 
>> +	}
>> +	reg->ops = ops;
>> +	reg->priv = priv;
>> +	dpll->type = type;
>> +	first_registration = list_empty(&dpll->registration_list);
>> +	list_add_tail(&reg->list, &dpll->registration_list);
>> +	if (!first_registration) {
>> +		mutex_unlock(&dpll_lock);
>> +		return 0;
>> +	}
>> +
>> +	xa_set_mark(&dpll_device_xa, dpll->id, DPLL_REGISTERED);
>> +	mutex_unlock(&dpll_lock);
>> +	dpll_device_create_ntf(dpll);
>> +
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(dpll_device_register);
>> +
>> +/**
>> + * dpll_device_unregister - unregister dpll device
>> + * @dpll: registered dpll pointer
>> + * @ops: ops for a dpll device
>> + * @priv: pointer to private information of owner
>> + *
>> + * Unregister device, make it unavailable for userspace.
>> + * Note: It does not free the memory
>> + * Context: Acquires a lock (dpll_lock)
>> + */
>> +void dpll_device_unregister(struct dpll_device *dpll,
>> +			    const struct dpll_device_ops *ops, void *priv)
>> +{
>> +	struct dpll_device_registration *reg;
>> +
>> +	mutex_lock(&dpll_lock);
>> +	ASSERT_DPLL_REGISTERED(dpll);
>> +	dpll_device_delete_ntf(dpll);
>> +	reg = dpll_device_registration_find(dpll, ops, priv);
>> +	if (WARN_ON(!reg)) {
>> +		mutex_unlock(&dpll_lock);
>> +		return;
>> +	}
>> +	list_del(&reg->list);
>> +	kfree(reg);
>> +
>> +	if (!list_empty(&dpll->registration_list)) {
>> +		mutex_unlock(&dpll_lock);
>> +		return;
>> +	}
>> +	xa_clear_mark(&dpll_device_xa, dpll->id, DPLL_REGISTERED);
>> +	mutex_unlock(&dpll_lock);
>> +}
>> +EXPORT_SYMBOL_GPL(dpll_device_unregister);
>> +
>> +/**
>> + * dpll_pin_alloc - allocate the memory for dpll pin
>> + * @clock_id: clock_id of creator
>> + * @pin_idx: idx given by dev driver
>> + * @module: reference to registering module
>> + * @prop: dpll pin properties
>> + *
>> + * Context: shall be called under a lock (dpll_lock)
>> + * Return:
>> + * * valid allocated dpll_pin struct pointer if succeeded
>> + * * ERR_PTR(-ENOMEM) - failed memory allocation
>> + * * ERR_PTR(-EINVAL) - wrong pin type property value
>> + */
>> +static struct dpll_pin *
>> +dpll_pin_alloc(u64 clock_id, u32 pin_idx, struct module *module,
>> +	       const struct dpll_pin_properties *prop)
>> +{
>> +	struct dpll_pin *pin;
>> +	int ret;
>> +
>> +	pin = kzalloc(sizeof(*pin), GFP_KERNEL);
>> +	if (!pin)
>> +		return ERR_PTR(-ENOMEM);
>> +	pin->pin_idx = pin_idx;
>> +	pin->clock_id = clock_id;
>> +	pin->module = module;
>> +	if (WARN_ON(prop->type < DPLL_PIN_TYPE_MUX ||
>> +		    prop->type > DPLL_PIN_TYPE_MAX)) {
>> +		ret = -EINVAL;
>> +		goto err;
>> +	}
>> +	pin->prop = prop;
>> +	refcount_set(&pin->refcount, 1);
>> +	xa_init_flags(&pin->dpll_refs, XA_FLAGS_ALLOC);
>> +	xa_init_flags(&pin->parent_refs, XA_FLAGS_ALLOC);
>> +	ret = xa_alloc(&dpll_pin_xa, &pin->id, pin, xa_limit_16b, GFP_KERNEL);
>> +	if (ret)
>> +		goto err;
>> +	return pin;
>> +err:
>> +	xa_destroy(&pin->dpll_refs);
>> +	xa_destroy(&pin->parent_refs);
>> +	kfree(pin);
>> +	return ERR_PTR(ret);
>> +}
>> +
>> +/**
>> + * dpll_pin_get - find existing or create new dpll pin
>> + * @clock_id: clock_id of creator
>> + * @pin_idx: idx given by dev driver
>> + * @module: reference to registering module
>> + * @prop: dpll pin properties
>> + *
>> + * Get existing object of a pin (unique for given arguments) or create new
>> + * if doesn't exist yet.
>> + *
>> + * Context: shall be called under a lock (dpll_lock)
>> + * Return:
>> + * * valid allocated dpll_pin struct pointer if succeeded
>> + * * ERR_PTR of an error
>> + */
>> +struct dpll_pin *
>> +dpll_pin_get(u64 clock_id, u32 pin_idx, struct module *module,
>> +	     const struct dpll_pin_properties *prop)
>> +{
>> +	struct dpll_pin *pos, *ret = NULL;
>> +	unsigned long i;
>> +
>> +	xa_for_each(&dpll_pin_xa, i, pos) {
>> +		if (pos->clock_id == clock_id &&
>> +		    pos->pin_idx == pin_idx &&
>> +		    pos->module == module) {
>> +			ret = pos;
>> +			refcount_inc(&ret->refcount);
>> +			break;
>> +		}
>> +	}
>> +	if (!ret)
>> +		ret = dpll_pin_alloc(clock_id, pin_idx, module, prop);
>> +
>> +	return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(dpll_pin_get);
>> +
>> +/**
>> + * dpll_pin_put - decrease the refcount and free memory if possible
>> + * @pin: pointer to a pin to be put
>> + *
>> + * Drop reference for a pin, if all references are gone, delete pin object.
>> + *
>> + * Context: shall be called under a lock (dpll_lock)
>> + */
>> +void dpll_pin_put(struct dpll_pin *pin)
>> +{
>> +	if (!pin)
> 
> Drop this check.
> 
> 
>> +		return;
>> +	if (refcount_dec_and_test(&pin->refcount)) {
>> +		xa_destroy(&pin->dpll_refs);
>> +		xa_destroy(&pin->parent_refs);
>> +		xa_erase(&dpll_pin_xa, pin->id);
>> +		kfree(pin);
>> +	}
>> +}
>> +EXPORT_SYMBOL_GPL(dpll_pin_put);
>> +
>> +static int
>> +__dpll_pin_register(struct dpll_device *dpll, struct dpll_pin *pin,
>> +		    const struct dpll_pin_ops *ops, void *priv)
>> +{
>> +	int ret;
>> +
>> +	if (WARN_ON(!ops))
>> +		return -EINVAL;
>> +
>> +	ret = dpll_xa_ref_pin_add(&dpll->pin_refs, pin, ops, priv);
>> +	if (ret)
>> +		return ret;
>> +	ret = dpll_xa_ref_dpll_add(&pin->dpll_refs, dpll, ops, priv);
>> +	if (ret)
>> +		goto ref_pin_del;
>> +	else
>> +		dpll_pin_create_ntf(pin);
>> +
>> +	return ret;
>> +
>> +ref_pin_del:
>> +	dpll_xa_ref_pin_del(&dpll->pin_refs, pin, ops, priv);
>> +	return ret;
>> +}
>> +
>> +/**
>> + * dpll_pin_register - register the dpll pin in the subsystem
>> + * @dpll: pointer to a dpll
>> + * @pin: pointer to a dpll pin
>> + * @ops: ops for a dpll pin ops
>> + * @priv: pointer to private information of owner
>> + *
>> + * Context: Acquires a lock (dpll_lock)
>> + * Return:
>> + * * 0 on success
>> + * * -EINVAL - missing pin ops
>> + * * -ENOMEM - failed to allocate memory
>> + */
>> +int
>> +dpll_pin_register(struct dpll_device *dpll, struct dpll_pin *pin,
>> +		  const struct dpll_pin_ops *ops, void *priv)
>> +{
>> +	int ret;
>> +
>> +	mutex_lock(&dpll_lock);
>> +	if (WARN_ON(!(dpll->module == pin->module &&
>> +		      dpll->clock_id == pin->clock_id)))
>> +		ret = -EFAULT;
> 
> In other cases like this you return -EINVAL. I think it is better. One
> way or another, be consistent please.
> 
> 
>> +	else
>> +		ret = __dpll_pin_register(dpll, pin, ops, priv);
>> +	mutex_unlock(&dpll_lock);
>> +
>> +	return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(dpll_pin_register);
>> +
>> +static void
>> +__dpll_pin_unregister(struct dpll_device *dpll, struct dpll_pin *pin,
>> +		      const struct dpll_pin_ops *ops, void *priv)
>> +{
>> +	dpll_xa_ref_pin_del(&dpll->pin_refs, pin, ops, priv);
>> +	dpll_xa_ref_dpll_del(&pin->dpll_refs, dpll, ops, priv);
>> +}
>> +
>> +/**
>> + * dpll_pin_unregister - unregister dpll pin from dpll device
>> + * @dpll: registered dpll pointer
>> + * @pin: pointer to a pin
>> + * @ops: ops for a dpll pin
>> + * @priv: pointer to private information of owner
>> + *
>> + * Note: It does not free the memory
>> + * Context: Acquires a lock (dpll_lock)
>> + */
>> +void dpll_pin_unregister(struct dpll_device *dpll, struct dpll_pin *pin,
>> +			 const struct dpll_pin_ops *ops, void *priv)
>> +{
>> +	if (WARN_ON(xa_empty(&dpll->pin_refs)))
>> +		return;
>> +
>> +	mutex_lock(&dpll_lock);
>> +	__dpll_pin_unregister(dpll, pin, ops, priv);
>> +	mutex_unlock(&dpll_lock);
>> +}
>> +EXPORT_SYMBOL_GPL(dpll_pin_unregister);
>> +
>> +/**
>> + * dpll_pin_on_pin_register - register a pin with a parent pin
>> + * @parent: pointer to a parent pin
>> + * @pin: pointer to a pin
>> + * @ops: ops for a dpll pin
>> + * @priv: pointer to private information of owner
>> + *
>> + * Register a pin with a parent pin, create references between them and
>> + * between newly registered pin and dplls connected with a parent pin.
>> + *
>> + * Context: Acquires a lock (dpll_lock)
>> + * Return:
>> + * * 0 on success
>> + * * -EINVAL missing pin or parent
>> + * * -ENOMEM failed allocation
>> + * * -EPERM if parent is not allowed
>> + */
>> +int dpll_pin_on_pin_register(struct dpll_pin *parent, struct dpll_pin *pin,
>> +			     const struct dpll_pin_ops *ops, void *priv)
>> +{
>> +	struct dpll_pin_ref *ref;
>> +	unsigned long i, stop;
>> +	int ret;
>> +
>> +	if (WARN_ON(parent->prop->type != DPLL_PIN_TYPE_MUX))
>> +		return -EINVAL;
>> +	ret = dpll_xa_ref_pin_add(&pin->parent_refs, parent, ops, priv);
>> +	if (ret)
>> +		goto unlock;
>> +	refcount_inc(&pin->refcount);
>> +	xa_for_each(&parent->dpll_refs, i, ref) {
>> +		mutex_lock(&dpll_lock);
>> +		ret = __dpll_pin_register(ref->dpll, pin, ops, priv);
>> +		mutex_unlock(&dpll_lock);
>> +		if (ret) {
>> +			stop = i;
>> +			goto dpll_unregister;
>> +		}
>> +		dpll_pin_create_ntf(pin);
>> +	}
>> +
>> +	return ret;
>> +
>> +dpll_unregister:
>> +	xa_for_each(&parent->dpll_refs, i, ref) {
>> +		if (i < stop) {
>> +			mutex_lock(&dpll_lock);
>> +			__dpll_pin_unregister(ref->dpll, pin, ops, priv);
>> +			mutex_unlock(&dpll_lock);
>> +		}
>> +	}
>> +	refcount_dec(&pin->refcount);
>> +	dpll_xa_ref_pin_del(&pin->parent_refs, parent, ops, priv);
>> +unlock:
>> +	return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(dpll_pin_on_pin_register);
>> +
>> +/**
>> + * dpll_pin_on_pin_unregister - unregister dpll pin from a parent pin
>> + * @parent: pointer to a parent pin
>> + * @pin: pointer to a pin
>> + * @ops: ops for a dpll pin
>> + * @priv: pointer to private information of owner
>> + *
>> + * Context: Acquires a lock (dpll_lock)
>> + * Note: It does not free the memory
>> + */
>> +void dpll_pin_on_pin_unregister(struct dpll_pin *parent, struct dpll_pin *pin,
>> +				const struct dpll_pin_ops *ops, void *priv)
>> +{
>> +	struct dpll_pin_ref *ref;
>> +	unsigned long i;
>> +
>> +	mutex_lock(&dpll_lock);
>> +	dpll_pin_delete_ntf(pin);
>> +	dpll_xa_ref_pin_del(&pin->parent_refs, parent, ops, priv);
>> +	refcount_dec(&pin->refcount);
>> +	xa_for_each(&pin->dpll_refs, i, ref) {
>> +		__dpll_pin_unregister(ref->dpll, pin, ops, priv);
>> +	}
> 
> Drop "{}"s for one line statement. Didn't checkpack warn you?
> 
> 
>> +	mutex_unlock(&dpll_lock);
>> +}
>> +EXPORT_SYMBOL_GPL(dpll_pin_on_pin_unregister);
>> +
>> +
>> +/**
>> + * dpll_device_registration_first - get first registration of dpll device
>> + * @dpll: pointer to a dpll
>> + *
>> + * Context: shall be called under a lock (dpll_lock)
>> + * Return: pointer to the first registration of a dpll
>> + */
>> +static struct dpll_device_registration *
>> +dpll_device_registration_first(struct dpll_device *dpll)
>> +{
>> +	struct dpll_device_registration *reg;
>> +
>> +	reg = list_first_entry_or_null((struct list_head *) &dpll->registration_list,
>> +				       struct dpll_device_registration, list);
>> +	WARN_ON(!reg);
>> +	return reg;
>> +}
>> +
>> +/**
>> + * dpll_priv - get the dpll device private owner data
>> + * @dpll: registered dpll pointer
>> + *
>> + * Context: shall be called under a lock (dpll_lock)
>> + * Return: pointer to the first registration priv data
>> + */
>> +void *dpll_priv(struct dpll_device *dpll)
>> +{
>> +	struct dpll_device_registration *reg;
>> +
>> +	reg = dpll_device_registration_first(dpll);
>> +	return reg->priv;
>> +}
>> +
>> +/**
>> + * dpll_device_ops - get the dpll device ops pointer
>> + * @dpll: registered dpll pointer
>> + *
>> + * Context: shall be called under a lock (dpll_lock)
>> + * Return: pointer to the first registration ops of the dpll
>> + */
>> +const struct dpll_device_ops *dpll_device_ops(struct dpll_device *dpll)
>> +{
>> +	struct dpll_device_registration *reg;
>> +
>> +	reg = dpll_device_registration_first(dpll);
>> +	return reg->ops;
>> +}
>> +
>> +/**
>> + * dpll_pin_registration_first - get first registration of dpll pin ref
>> + * @ref: pointer to a pin ref struct
>> + *
>> + * Context: shall be called under a lock (dpll_lock)
>> + * Return: pointer to the first registration of a dpll_pin_ref
>> + */
>> +static struct dpll_pin_registration *
>> +dpll_pin_registration_first(struct dpll_pin_ref *ref)
>> +{
>> +	struct dpll_pin_registration *reg;
>> +
>> +	reg = list_first_entry_or_null(&ref->registration_list,
>> +				       struct dpll_pin_registration, list);
>> +	WARN_ON(!reg);
>> +	return reg;
>> +}
>> +
>> +/**
>> + * dpll_pin_on_dpll_priv - get the dpll device private owner data
>> + * @dpll:      registered dpll pointer
>> + * @pin:       pointer to a pin
>> + *
>> + * Context: shall be called under a lock (dpll_lock)
>> + * Return: pointer to the data
>> + */
>> +void *dpll_pin_on_dpll_priv(struct dpll_device *dpll,
>> +			    struct dpll_pin *pin)
>> +{
>> +	struct dpll_pin_registration *reg;
>> +	struct dpll_pin_ref *ref;
>> +
>> +	ref = xa_load(&dpll->pin_refs, pin->pin_idx);
>> +	if (!ref)
>> +		return NULL;
>> +	reg = dpll_pin_registration_first(ref);
>> +	return reg->priv;
>> +}
>> +
>> +/**
>> + * dpll_pin_on_pin_priv - get the dpll pin private owner data
>> + * @parent: pointer to a parent pin
>> + * @pin: pointer to a pin
>> + *
>> + * Context: shall be called under a lock (dpll_lock)
>> + * Return: pointer to the data
>> + */
>> +void *dpll_pin_on_pin_priv(struct dpll_pin *parent,
>> +			   struct dpll_pin *pin)
>> +{
>> +	struct dpll_pin_registration *reg;
>> +	struct dpll_pin_ref *ref;
>> +
>> +	ref = xa_load(&pin->parent_refs, parent->pin_idx);
>> +	if (!ref)
>> +		return NULL;
>> +	reg = dpll_pin_registration_first(ref);
>> +	return reg->priv;
>> +}
>> +
>> +/**
>> + * dpll_pin_ops - get the pin ops pointer
>> + * @ref: dpll pin ref
>> + *
>> + * Context: shall be called under a lock (dpll_lock)
>> + * Return: pointer to the first ops registered with the pin
>> + */
>> +const struct dpll_pin_ops *dpll_pin_ops(struct dpll_pin_ref *ref)
>> +{
>> +	struct dpll_pin_registration *reg;
>> +
>> +	reg = dpll_pin_registration_first(ref);
>> +	return reg->ops;
>> +}
>> +
>> +/**
>> + * dpll_init - initialize dpll subsystem
>> + *
>> + * Return:
>> + * 0 - success
>> + * negative - netlink init error
>> + */
>> +static int __init dpll_init(void)
>> +{
>> +	int ret;
>> +
>> +	ret = dpll_netlink_init();
>> +	if (ret)
>> +		goto error;
>> +
>> +	return 0;
>> +
>> +error:
>> +	mutex_destroy(&dpll_lock);
>> +	return ret;
>> +}
>> +subsys_initcall(dpll_init);
>> diff --git a/drivers/dpll/dpll_core.h b/drivers/dpll/dpll_core.h
>> new file mode 100644
>> index 000000000000..ef95e272937c
>> --- /dev/null
>> +++ b/drivers/dpll/dpll_core.h
>> @@ -0,0 +1,104 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/*
>> + *  Copyright (c) 2023 Meta Platforms, Inc. and affiliates
>> + *  Copyright (c) 2023 Intel and affiliates
>> + */
>> +
>> +#ifndef __DPLL_CORE_H__
>> +#define __DPLL_CORE_H__
>> +
>> +#include <linux/dpll.h>
>> +#include <linux/list.h>
>> +#include <linux/refcount.h>
>> +#include "dpll_netlink.h"
>> +
>> +#define DPLL_REGISTERED		XA_MARK_1
>> +
>> +struct dpll_device_registration {
>> +	struct list_head list;
>> +	const struct dpll_device_ops *ops;
>> +	void *priv;
> 
> You don't need this struct in the header. Move to .c
> 
> 
>> +};
>> +
>> +/**
>> + * struct dpll_device - stores DPLL device internal data
>> + * @id:			unique id number for each device given by kernel
> 
> Who's kernel? Say "dpll subsystem" instead.
> 
> 
>> + * @device_idx:		id given by dev driver
>> + * @clock_id:		unique identifier (clock_id) of a dpll
>> + * @module:		module of creator
>> + * @type:		type of a dpll
>> + * @pin_refs:		stores pins registered within a dpll
>> + * @mode_supported_mask: mask of supported modes
>> + * @refcount:		refcount
>> + * @registration_list:	list of registered ops and priv data of dpll owners
>> + **/
>> +struct dpll_device {
>> +	u32 id;
>> +	u32 device_idx;
>> +	u64 clock_id;
>> +	struct module *module;
>> +	enum dpll_type type;
>> +	struct xarray pin_refs;
>> +	unsigned long mode_supported_mask;
>> +	refcount_t refcount;
>> +	struct list_head registration_list;
>> +};
>> +
>> +/**
>> + * struct dpll_pin - structure for a dpll pin
>> + * @id:			unique id number for pin given by kernel
> 
> Who's kernel? Say "dpll subsystem" instead.
> 
> 
>> + * @pin_idx:		index of a pin given by dev driver
>> + * @clock_id:		clock_id of creator
>> + * @module:		module of creator
>> + * @dpll_refs:		hold referencees to dplls pin was registered with
>> + * @parent_refs:	hold references to parent pins pin was registered with
>> + * @prop:		pointer to pin properties given by registerer
>> + * @rclk_dev_name:	holds name of device when pin can recover clock from it
>> + * @refcount:		refcount
>> + **/
>> +struct dpll_pin {
>> +	u32 id;
>> +	u32 pin_idx;
>> +	u64 clock_id;
>> +	struct module *module;
>> +	struct xarray dpll_refs;
>> +	struct xarray parent_refs;
>> +	const struct dpll_pin_properties *prop;
>> +	char *rclk_dev_name;
>> +	refcount_t refcount;
>> +};
>> +
>> +struct dpll_pin_registration {
>> +	struct list_head list;
>> +	const struct dpll_pin_ops *ops;
>> +	void *priv;
>> +};
> 
> You don't need this struct in the header. Move to .c
> 
> 
>> +
>> +/**
>> + * struct dpll_pin_ref - structure for referencing either dpll or pins
>> + * @dpll:		pointer to a dpll
>> + * @pin:		pointer to a pin
>> + * @registration_list:	list of ops and priv data registered with the ref
>> + * @refcount:		refcount
>> + **/
>> +struct dpll_pin_ref {
>> +	union {
>> +		struct dpll_device *dpll;
>> +		struct dpll_pin *pin;
>> +	};
>> +	struct list_head registration_list;
>> +	refcount_t refcount;
>> +};
>> +
>> +void *dpll_priv(struct dpll_device *dpll);
>> +void *dpll_pin_on_dpll_priv(struct dpll_device *dpll, struct dpll_pin *pin);
>> +void *dpll_pin_on_pin_priv(struct dpll_pin *parent, struct dpll_pin *pin);
>> +
>> +const struct dpll_device_ops *dpll_device_ops(struct dpll_device *dpll);
>> +struct dpll_device *dpll_device_get_by_id(int id);
>> +const struct dpll_pin_ops *dpll_pin_ops(struct dpll_pin_ref *ref);
>> +struct dpll_pin_ref *dpll_xa_ref_dpll_first(struct xarray *xa_refs);
>> +extern struct xarray dpll_device_xa;
>> +extern struct xarray dpll_pin_xa;
>> +extern struct mutex dpll_lock;
>> +#endif
>> -- 
>> 2.37.3
>>