[PATCH v7 3/9] PCI: endpoint: Add auxiliary resource query API
Frank Li
Frank.li at nxp.com
Mon Feb 16 07:56:14 PST 2026
On Mon, Feb 16, 2026 at 01:38:41AM +0900, Koichiro Den wrote:
> Endpoint controller drivers may integrate auxiliary blocks (e.g. DMA
> engines) whose register windows and descriptor memories metadata need to
> be exposed to a remote peer. Endpoint function drivers need a generic
> way to discover such resources without hard-coding controller-specific
> helpers.
>
> Add pci_epc_get_aux_resources() and the corresponding pci_epc_ops
> get_aux_resources() callback. The API returns a list of resources
> described by type, physical address and size, plus type-specific
> metadata.
>
> Passing resources == NULL (or num_resources == 0) returns the required
> number of entries.
>
> Signed-off-by: Koichiro Den <den at valinux.co.jp>
> ---
Reviewed-by: Frank Li <Frank.Li at nxp.com>
> drivers/pci/endpoint/pci-epc-core.c | 41 +++++++++++++++++++++++
> include/linux/pci-epc.h | 51 +++++++++++++++++++++++++++++
> 2 files changed, 92 insertions(+)
>
> diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
> index 068155819c57..01de4bd5047a 100644
> --- a/drivers/pci/endpoint/pci-epc-core.c
> +++ b/drivers/pci/endpoint/pci-epc-core.c
> @@ -155,6 +155,47 @@ const struct pci_epc_features *pci_epc_get_features(struct pci_epc *epc,
> }
> EXPORT_SYMBOL_GPL(pci_epc_get_features);
>
> +/**
> + * pci_epc_get_aux_resources() - query EPC-provided auxiliary resources
> + * @epc: EPC device
> + * @func_no: function number
> + * @vfunc_no: virtual function number
> + * @resources: output array (may be NULL to query required count)
> + * @num_resources: size of @resources array in entries (0 when querying count)
> + *
> + * Some EPC backends integrate auxiliary blocks (e.g. DMA engines) whose control
> + * registers and/or descriptor memories can be exposed to the host by mapping
> + * them into BAR space. This helper queries the backend for such resources.
> + *
> + * Return:
> + * * >= 0: number of resources returned (or required, if @resources is NULL)
> + * * -EOPNOTSUPP: backend does not support auxiliary resource queries
> + * * other -errno on failure
> + */
> +int pci_epc_get_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> + struct pci_epc_aux_resource *resources,
> + int num_resources)
> +{
> + int ret;
> +
> + if (!epc || !epc->ops)
> + return -EINVAL;
> +
> + if (func_no >= epc->max_functions)
> + return -EINVAL;
> +
> + if (!epc->ops->get_aux_resources)
> + return -EOPNOTSUPP;
> +
> + mutex_lock(&epc->lock);
> + ret = epc->ops->get_aux_resources(epc, func_no, vfunc_no, resources,
> + num_resources);
> + mutex_unlock(&epc->lock);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(pci_epc_get_aux_resources);
> +
> /**
> * pci_epc_stop() - stop the PCI link
> * @epc: the link of the EPC device that has to be stopped
> diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
> index 7a87f5962dd0..fd79784b31db 100644
> --- a/include/linux/pci-epc.h
> +++ b/include/linux/pci-epc.h
> @@ -61,6 +61,50 @@ struct pci_epc_map {
> void __iomem *virt_addr;
> };
>
> +/**
> + * enum pci_epc_aux_resource_type - auxiliary resource type identifiers
> + * @PCI_EPC_AUX_DMA_CTRL_MMIO: Integrated DMA controller register window (MMIO)
> + * @PCI_EPC_AUX_DMA_CHAN_DESC: Per-channel DMA descriptor
> + * @PCI_EPC_AUX_DOORBELL_MMIO: Doorbell MMIO, that might be outside the DMA
> + * controller register window
> + *
> + * EPC backends may expose auxiliary blocks (e.g. DMA engines) by mapping their
> + * register windows and descriptor memories into BAR space. This enum
> + * identifies the type of each exposable resource.
> + */
> +enum pci_epc_aux_resource_type {
> + PCI_EPC_AUX_DMA_CTRL_MMIO,
> + PCI_EPC_AUX_DMA_CHAN_DESC,
> + PCI_EPC_AUX_DOORBELL_MMIO,
> +};
> +
> +/**
> + * struct pci_epc_aux_resource - a physical auxiliary resource that may be
> + * exposed for peer use
> + * @type: resource type, see enum pci_epc_aux_resource_type
> + * @phys_addr: physical base address of the resource
> + * @size: size of the resource in bytes
> + * @bar: BAR number where this resource is already exposed to the RC
> + * (NO_BAR if not)
> + * @bar_offset: offset within @bar where the resource starts (valid iff
> + * @bar != NO_BAR)
> + * @u: type-specific metadata
> + */
> +struct pci_epc_aux_resource {
> + enum pci_epc_aux_resource_type type;
> + phys_addr_t phys_addr;
> + resource_size_t size;
> + enum pci_barno bar;
> + resource_size_t bar_offset;
> +
> + union {
> + /* PCI_EPC_AUX_DOORBELL_MMIO */
> + struct {
> + int irq;
> + } db_mmio;
> + } u;
> +};
> +
> /**
> * struct pci_epc_ops - set of function pointers for performing EPC operations
> * @write_header: ops to populate configuration space header
> @@ -84,6 +128,7 @@ struct pci_epc_map {
> * @start: ops to start the PCI link
> * @stop: ops to stop the PCI link
> * @get_features: ops to get the features supported by the EPC
> + * @get_aux_resources: ops to retrieve controller-owned auxiliary resources
> * @owner: the module owner containing the ops
> */
> struct pci_epc_ops {
> @@ -115,6 +160,9 @@ struct pci_epc_ops {
> void (*stop)(struct pci_epc *epc);
> const struct pci_epc_features* (*get_features)(struct pci_epc *epc,
> u8 func_no, u8 vfunc_no);
> + int (*get_aux_resources)(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> + struct pci_epc_aux_resource *resources,
> + int num_resources);
> struct module *owner;
> };
>
> @@ -337,6 +385,9 @@ int pci_epc_start(struct pci_epc *epc);
> void pci_epc_stop(struct pci_epc *epc);
> const struct pci_epc_features *pci_epc_get_features(struct pci_epc *epc,
> u8 func_no, u8 vfunc_no);
> +int pci_epc_get_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> + struct pci_epc_aux_resource *resources,
> + int num_resources);
> enum pci_barno
> pci_epc_get_first_free_bar(const struct pci_epc_features *epc_features);
> enum pci_barno pci_epc_get_next_free_bar(const struct pci_epc_features
> --
> 2.51.0
>
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