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Message-ID: <20260204145440.950609-7-den@valinux.co.jp>
Date: Wed, 4 Feb 2026 23:54:34 +0900
From: Koichiro Den <den@...inux.co.jp>
To: vkoul@...nel.org,
mani@...nel.org,
Frank.Li@....com,
jingoohan1@...il.com,
lpieralisi@...nel.org,
kwilczynski@...nel.org,
robh@...nel.org,
bhelgaas@...gle.com
Cc: dmaengine@...r.kernel.org,
linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v3 06/11] PCI: endpoint: Add remote resource query API
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_remote_resources() and the corresponding pci_epc_ops
get_remote_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@...inux.co.jp>
---
drivers/pci/endpoint/pci-epc-core.c | 41 +++++++++++++++++++++++++
include/linux/pci-epc.h | 46 +++++++++++++++++++++++++++++
2 files changed, 87 insertions(+)
diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
index 068155819c57..fa161113e24c 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_remote_resources() - query EPC-provided remote 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 remote resource queries
+ * * other -errno on failure
+ */
+int pci_epc_get_remote_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
+ struct pci_epc_remote_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_remote_resources)
+ return -EOPNOTSUPP;
+
+ mutex_lock(&epc->lock);
+ ret = epc->ops->get_remote_resources(epc, func_no, vfunc_no,
+ resources, num_resources);
+ mutex_unlock(&epc->lock);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(pci_epc_get_remote_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 c021c7af175f..af60d4ad2f0e 100644
--- a/include/linux/pci-epc.h
+++ b/include/linux/pci-epc.h
@@ -61,6 +61,44 @@ struct pci_epc_map {
void __iomem *virt_addr;
};
+/**
+ * enum pci_epc_remote_resource_type - remote resource type identifiers
+ * @PCI_EPC_RR_DMA_CTRL_MMIO: Integrated DMA controller register window (MMIO)
+ * @PCI_EPC_RR_DMA_CHAN_DESC: Per-channel DMA descriptor
+ *
+ * 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_remote_resource_type {
+ PCI_EPC_RR_DMA_CTRL_MMIO,
+ PCI_EPC_RR_DMA_CHAN_DESC,
+};
+
+/**
+ * struct pci_epc_remote_resource - a physical resource that can be exposed
+ * @type: resource type, see enum pci_epc_remote_resource_type
+ * @phys_addr: physical base address of the resource
+ * @size: size of the resource in bytes
+ * @u: type-specific metadata
+ *
+ * For @PCI_EPC_RR_DMA_CHAN_DESC, @u.dma_chan_desc provides per-channel
+ * information.
+ */
+struct pci_epc_remote_resource {
+ enum pci_epc_remote_resource_type type;
+ phys_addr_t phys_addr;
+ resource_size_t size;
+
+ union {
+ /* PCI_EPC_RR_DMA_CHAN_DESC */
+ struct {
+ u16 hw_chan_id;
+ bool ep2rc;
+ } dma_chan_desc;
+ } u;
+};
+
/**
* struct pci_epc_ops - set of function pointers for performing EPC operations
* @write_header: ops to populate configuration space header
@@ -84,6 +122,8 @@ 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_remote_resources: ops to retrieve controller-owned resources that can be
+ * exposed to the remote host (optional)
* @owner: the module owner containing the ops
*/
struct pci_epc_ops {
@@ -115,6 +155,9 @@ 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_remote_resources)(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
+ struct pci_epc_remote_resource *resources,
+ int num_resources);
struct module *owner;
};
@@ -309,6 +352,9 @@ 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_remote_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
+ struct pci_epc_remote_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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