linux/drivers/pci/pci-bridge-emul.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2018 Marvell
 *
 * Author: Thomas Petazzoni <[email protected]>
 *
 * This file helps PCI controller drivers implement a fake root port
 * PCI bridge when the HW doesn't provide such a root port PCI
 * bridge.
 *
 * It emulates a PCI bridge by providing a fake PCI configuration
 * space (and optionally a PCIe capability configuration space) in
 * memory. By default the read/write operations simply read and update
 * this fake configuration space in memory. However, PCI controller
 * drivers can provide through the 'struct pci_sw_bridge_ops'
 * structure a set of operations to override or complement this
 * default behavior.
 */

#include <linux/pci.h>
#include "pci-bridge-emul.h"

#define PCI_BRIDGE_CONF_END …
#define PCI_CAP_SSID_SIZEOF …
#define PCI_CAP_PCIE_SIZEOF …

/**
 * struct pci_bridge_reg_behavior - register bits behaviors
 * @ro:		Read-Only bits
 * @rw:		Read-Write bits
 * @w1c:	Write-1-to-Clear bits
 *
 * Reads and Writes will be filtered by specified behavior. All other bits not
 * declared are assumed 'Reserved' and will return 0 on reads, per PCIe 5.0:
 * "Reserved register fields must be read only and must return 0 (all 0's for
 * multi-bit fields) when read".
 */
struct pci_bridge_reg_behavior { … };

static const
struct pci_bridge_reg_behavior pci_regs_behavior[PCI_STD_HEADER_SIZEOF / 4] = …;

static const
struct pci_bridge_reg_behavior pcie_cap_regs_behavior[PCI_CAP_PCIE_SIZEOF / 4] = …;

static pci_bridge_emul_read_status_t
pci_bridge_emul_read_ssid(struct pci_bridge_emul *bridge, int reg, u32 *value)
{ … }

/*
 * Initialize a pci_bridge_emul structure to represent a fake PCI
 * bridge configuration space. The caller needs to have initialized
 * the PCI configuration space with whatever values make sense
 * (typically at least vendor, device, revision), the ->ops pointer,
 * and optionally ->data and ->has_pcie.
 */
int pci_bridge_emul_init(struct pci_bridge_emul *bridge,
			 unsigned int flags)
{ … }
EXPORT_SYMBOL_GPL(…);

/*
 * Cleanup a pci_bridge_emul structure that was previously initialized
 * using pci_bridge_emul_init().
 */
void pci_bridge_emul_cleanup(struct pci_bridge_emul *bridge)
{ … }
EXPORT_SYMBOL_GPL(…);

/*
 * Should be called by the PCI controller driver when reading the PCI
 * configuration space of the fake bridge. It will call back the
 * ->ops->read_base or ->ops->read_pcie operations.
 */
int pci_bridge_emul_conf_read(struct pci_bridge_emul *bridge, int where,
			      int size, u32 *value)
{ … }
EXPORT_SYMBOL_GPL(…);

/*
 * Should be called by the PCI controller driver when writing the PCI
 * configuration space of the fake bridge. It will call back the
 * ->ops->write_base or ->ops->write_pcie operations.
 */
int pci_bridge_emul_conf_write(struct pci_bridge_emul *bridge, int where,
			       int size, u32 value)
{ … }
EXPORT_SYMBOL_GPL(…);