Re: [PATCH v4 05/14] cxl: Simplify cxl_root_ops allocation and handling

Dave Jiang
2025-11-03T21:53:41Z

On 11/3/25 11:47 AM, Robert Richter wrote:
> A root port's callback handlers are collected in struct cxl_root_ops.
> The structure is dynamically allocated, though it contains only a
> single pointer in it. This also requires to check two pointers to
> check for the existance of a callback.
>
> Simplify the allocation, release and handler check by embedding the
> ops statical in struct cxl_root.
>
> Signed-off-by: Robert Richter <rrichter@amd.com>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>> ---
> drivers/cxl/acpi.c | 7 ++-----
> drivers/cxl/core/cdat.c | 8 ++++----
> drivers/cxl/core/port.c | 9 ++-------
> drivers/cxl/cxl.h | 19 ++++++++++---------
> 4 files changed, 18 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index bd2e282ca93a..1ab780edf141 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -299,10 +299,6 @@ static int cxl_acpi_qos_class(struct cxl_root *cxl_root,
> return cxl_acpi_evaluate_qtg_dsm(handle, coord, entries, qos_class);
> }
>
> -static const struct cxl_root_ops acpi_root_ops = {
> - .qos_class = cxl_acpi_qos_class,
> -};
> -
> static void del_cxl_resource(struct resource *res)
> {
> if (!res)
> @@ -914,9 +910,10 @@ static int cxl_acpi_probe(struct platform_device *pdev)
> cxl_res->end = -1;
> cxl_res->flags = IORESOURCE_MEM;
>
> - cxl_root = devm_cxl_add_root(host, &acpi_root_ops);
> + cxl_root = devm_cxl_add_root(host);
> if (IS_ERR(cxl_root))
> return PTR_ERR(cxl_root);
> + cxl_root->ops.qos_class = cxl_acpi_qos_class;
> root_port = &cxl_root->port;
>
> rc = bus_for_each_dev(adev->dev.bus, NULL, root_port,
> diff --git a/drivers/cxl/core/cdat.c b/drivers/cxl/core/cdat.c
> index c4bd6e8a0cf0..b84a9b52942c 100644
> --- a/drivers/cxl/core/cdat.c
> +++ b/drivers/cxl/core/cdat.c
> @@ -213,7 +213,7 @@ static int cxl_port_perf_data_calculate(struct cxl_port *port,
> if (!cxl_root)
> return -ENODEV;
>
> - if (!cxl_root->ops || !cxl_root->ops->qos_class)
> + if (!cxl_root->ops.qos_class)
> return -EOPNOTSUPP;
>
> xa_for_each(dsmas_xa, index, dent) {
> @@ -221,9 +221,9 @@ static int cxl_port_perf_data_calculate(struct cxl_port *port,
>
> cxl_coordinates_combine(dent->coord, dent->cdat_coord, ep_c);
> dent->entries = 1;
> - rc = cxl_root->ops->qos_class(cxl_root,
> - &dent->coord[ACCESS_COORDINATE_CPU],
> - 1, &qos_class);
> + rc = cxl_root->ops.qos_class(cxl_root,
> + &dent->coord[ACCESS_COORDINATE_CPU],
> + 1, &qos_class);
> if (rc != 1)
> continue;
>
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index 8128fd2b5b31..2338d146577c 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -459,7 +459,6 @@ static void cxl_root_decoder_release(struct device *dev)
> if (atomic_read(&cxlrd->region_id) >= 0)
> memregion_free(atomic_read(&cxlrd->region_id));
> __cxl_decoder_release(&cxlrd->cxlsd.cxld);
> - kfree(cxlrd->ops);
> kfree(cxlrd);
> }
>
> @@ -955,19 +954,15 @@ struct cxl_port *devm_cxl_add_port(struct device *host,
> }
> EXPORT_SYMBOL_NS_GPL(devm_cxl_add_port, "CXL");
>
> -struct cxl_root *devm_cxl_add_root(struct device *host,
> - const struct cxl_root_ops *ops)
> +struct cxl_root *devm_cxl_add_root(struct device *host)
> {
> - struct cxl_root *cxl_root;
> struct cxl_port *port;
>
> port = devm_cxl_add_port(host, host, CXL_RESOURCE_NONE, NULL);
> if (IS_ERR(port))
> return ERR_CAST(port);
>
> - cxl_root = to_cxl_root(port);
> - cxl_root->ops = ops;
> - return cxl_root;
> + return to_cxl_root(port);
> }
> EXPORT_SYMBOL_NS_GPL(devm_cxl_add_root, "CXL");
>
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index b57cfa4273b9..9a381c827416 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -638,6 +638,14 @@ struct cxl_port {
> resource_size_t component_reg_phys;
> };
>
> +struct cxl_root;
> +
> +struct cxl_root_ops {
> + int (*qos_class)(struct cxl_root *cxl_root,
> + struct access_coordinate *coord, int entries,
> + int *qos_class);
> +};
> +
> /**
> * struct cxl_root - logical collection of root cxl_port items
> *
> @@ -646,7 +654,7 @@ struct cxl_port {
> */
> struct cxl_root {
> struct cxl_port port;
> - const struct cxl_root_ops *ops;
> + struct cxl_root_ops ops;
> };
>
> static inline struct cxl_root *
> @@ -655,12 +663,6 @@ to_cxl_root(const struct cxl_port *port)
> return container_of(port, struct cxl_root, port);
> }
>
> -struct cxl_root_ops {
> - int (*qos_class)(struct cxl_root *cxl_root,
> - struct access_coordinate *coord, int entries,
> - int *qos_class);
> -};
> -
> static inline struct cxl_dport *
> cxl_find_dport_by_dev(struct cxl_port *port, const struct device *dport_dev)
> {
> @@ -755,8 +757,7 @@ struct cxl_port *devm_cxl_add_port(struct device *host,
> struct device *uport_dev,
> resource_size_t component_reg_phys,
> struct cxl_dport *parent_dport);
> -struct cxl_root *devm_cxl_add_root(struct device *host,
> - const struct cxl_root_ops *ops);
> +struct cxl_root *devm_cxl_add_root(struct device *host);
> struct cxl_root *find_cxl_root(struct cxl_port *port);
>
> DEFINE_FREE(put_cxl_root, struct cxl_root *, if (_T) put_device(&_T->port.dev))