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PCI(9) Kernel Developer's Manual PCI(9) NAME pci, pci_alloc_msi, pci_alloc_msix, pci_clear_pme, pci_disable_busmaster, pci_disable_io, pci_enable_busmaster, pci_enable_io, pci_enable_pme, pci_find_bsf, pci_find_cap, pci_find_dbsf, pci_find_device, pci_find_extcap, pci_find_htcap, pci_find_next_cap, pci_find_next_extcap, pci_find_next_htcap, pci_find_pcie_root_port, pci_get_id, pci_get_max_payload, pci_get_max_read_req, pci_get_powerstate, pci_get_vpd_ident, pci_get_vpd_readonly, pci_has_pm, pci_iov_attach, pci_iov_attach_name, pci_iov_detach, pci_msi_count, pci_msix_count, pci_msix_pba_bar, pci_msix_table_bar, pci_pending_msix, pci_read_config, pci_release_msi, pci_remap_msix, pci_restore_state, pci_save_state, pci_set_max_read_req, pci_set_powerstate, pci_write_config, pcie_adjust_config, pcie_flr, pcie_get_max_completion_timeout, pcie_read_config, pcie_wait_for_pending_transactions, pcie_write_config -- PCI bus interface SYNOPSIS #include <sys/bus.h> #include <dev/pci/pcireg.h> #include <dev/pci/pcivar.h> int pci_alloc_msi(device_t dev, int *count); int pci_alloc_msix(device_t dev, int *count); void pci_clear_pme(device_t dev); int pci_disable_busmaster(device_t dev); int pci_disable_io(device_t dev, int space); int pci_enable_busmaster(device_t dev); int pci_enable_io(device_t dev, int space); void pci_enable_pme(device_t dev); device_t pci_find_bsf(uint8_t bus, uint8_t slot, uint8_t func); int pci_find_cap(device_t dev, int capability, int *capreg); device_t pci_find_dbsf(uint32_t domain, uint8_t bus, uint8_t slot, uint8_t func); device_t pci_find_device(uint16_t vendor, uint16_t device); int pci_find_extcap(device_t dev, int capability, int *capreg); int pci_find_htcap(device_t dev, int capability, int *capreg); int pci_find_next_cap(device_t dev, int capability, int start, int *capreg); int pci_find_next_extcap(device_t dev, int capability, int start, int *capreg); int pci_find_next_htcap(device_t dev, int capability, int start, int *capreg); device_t pci_find_pcie_root_port(device_t dev); int pci_get_id(device_t dev, enum pci_id_type type, uintptr_t *id); int pci_get_max_payload(device_t dev); int pci_get_max_read_req(device_t dev); int pci_get_powerstate(device_t dev); int pci_get_vpd_ident(device_t dev, const char **identptr); int pci_get_vpd_readonly(device_t dev, const char *kw, const char **vptr); bool pci_has_pm(device_t dev); int pci_msi_count(device_t dev); int pci_msix_count(device_t dev); int pci_msix_pba_bar(device_t dev); int pci_msix_table_bar(device_t dev); int pci_pending_msix(device_t dev, u_int index); uint32_t pci_read_config(device_t dev, int reg, int width); int pci_release_msi(device_t dev); int pci_remap_msix(device_t dev, int count, const u_int *vectors); void pci_restore_state(device_t dev); void pci_save_state(device_t dev); int pci_set_max_read_req(device_t dev, int size); int pci_set_powerstate(device_t dev, int state); void pci_write_config(device_t dev, int reg, uint32_t val, int width); uint32_t pcie_adjust_config(device_t dev, int reg, uint32_t mask, uint32_t val, int width); bool pcie_flr(device_t dev, u_int max_delay, bool force); int pcie_get_max_completion_timeout(device_t dev); uint32_t pcie_read_config(device_t dev, int reg, int width); bool pcie_wait_for_pending_transactions(device_t dev, u_int max_delay); void pcie_write_config(device_t dev, int reg, uint32_t val, int width); void pci_event_fn(void *arg, device_t dev); EVENTHANDLER_REGISTER(pci_add_device, pci_event_fn); EVENTHANDLER_DEREGISTER(pci_delete_resource, pci_event_fn); #include <dev/pci/pci_iov.h> int pci_iov_attach(device_t dev, nvlist_t *pf_schema, nvlist_t *vf_schema); int pci_iov_attach_name(device_t dev, nvlist_t *pf_schema, nvlist_t *vf_schema, const char *fmt, ...); int pci_iov_detach(device_t dev); DESCRIPTION The pci set of functions are used for managing PCI devices. The func- tions are split into several groups: raw configuration access, locating devices, device information, device configuration, and message signaled interrupts. Raw Configuration Access The pci_read_config() function is used to read data from the PCI con- figuration space of the device dev, at offset reg, with width specify- ing the size of the access. The pci_write_config() function is used to write the value val to the PCI configuration space of the device dev, at offset reg, with width specifying the size of the access. The pcie_adjust_config() function is used to modify the value of a reg- ister in the PCI-express capability register set of device dev. The offset reg specifies a relative offset in the register set with width specifying the size of the access. The new value of the register is computed by modifying bits set in mask to the value in val. Any bits not specified in mask are preserved. The previous value of the regis- ter is returned. The pcie_read_config() function is used to read the value of a register in the PCI-express capability register set of device dev. The offset reg specifies a relative offset in the register set with width specify- ing the size of the access. The pcie_write_config() function is used to write the value val to a register in the PCI-express capability register set of device dev. The offset reg specifies a relative offset in the register set with width specifying the size of the access. NOTE: Device drivers should only use these functions for functionality that is not available via another pci() function. Locating Devices The pci_find_bsf() function looks up the device_t of a PCI device, given its bus, slot, and func. The slot number actually refers to the number of the device on the bus, which does not necessarily indicate its geographic location in terms of a physical slot. Note that in case the system has multiple PCI domains, the pci_find_bsf() function only searches the first one. Actually, it is equivalent to: pci_find_dbsf(0, bus, slot, func); The pci_find_dbsf() function looks up the device_t of a PCI device, given its domain, bus, slot, and func. The slot number actually refers to the number of the device on the bus, which does not necessarily in- dicate its geographic location in terms of a physical slot. The pci_find_device() function looks up the device_t of a PCI device, given its vendor and device IDs. Note that there can be multiple matches for this search; this function only returns the first matching device. Device Information The pci_find_cap() function is used to locate the first instance of a PCI capability register set for the device dev. The capability to lo- cate is specified by ID via capability. Constant macros of the form PCIY_xxx for standard capability IDs are defined in <dev/pci/pcireg.h>. If the capability is found, then *capreg is set to the offset in con- figuration space of the capability register set, and pci_find_cap() re- turns zero. If the capability is not found or the device does not sup- port capabilities, pci_find_cap() returns an error. The pci_find_next_cap() function is used to locate the next instance of a PCI capability register set for the device dev. The start should be the *capreg returned by a prior pci_find_cap() or pci_find_next_cap(). When no more instances are located pci_find_next_cap() returns an er- ror. The pci_has_pm() function returns true if dev supports power manage- ment. The pci_find_extcap() function is used to locate the first instance of a PCI-express extended capability register set for the device dev. The extended capability to locate is specified by ID via capability. Con- stant macros of the form PCIZ_xxx for standard extended capability IDs are defined in <dev/pci/pcireg.h>. If the extended capability is found, then *capreg is set to the offset in configuration space of the extended capability register set, and pci_find_extcap() returns zero. If the extended capability is not found or the device is not a PCI-ex- press device, pci_find_extcap() returns an error. The pci_find_next_extcap() function is used to locate the next instance of a PCI-express extended capability register set for the device dev. The start should be the *capreg returned by a prior pci_find_extcap() or pci_find_next_extcap(). When no more instances are located pci_find_next_extcap() returns an error. The pci_find_htcap() function is used to locate the first instance of a HyperTransport capability register set for the device dev. The capa- bility to locate is specified by type via capability. Constant macros of the form PCIM_HTCAP_xxx for standard HyperTransport capability types are defined in <dev/pci/pcireg.h>. If the capability is found, then *capreg is set to the offset in configuration space of the capability register set, and pci_find_htcap() returns zero. If the capability is not found or the device is not a HyperTransport device, pci_find_htcap() returns an error. The pci_find_next_htcap() function is used to locate the next instance of a HyperTransport capability reg- ister set for the device dev. The start should be the *capreg returned by a prior pci_find_htcap() or pci_find_next_htcap(). When no more in- stances are located pci_find_next_htcap() returns an error. The pci_find_pcie_root_port() function walks up the PCI device hierar- chy to locate the PCI-express root port upstream of dev. If a root port is not found, pci_find_pcie_root_port() returns NULL. The pci_get_id() function is used to read an identifier from a device. The type flag is used to specify which identifier to read. The follow- ing flags are supported: PCI_ID_RID Read the routing identifier for the device. PCI_ID_MSI Read the MSI routing ID. This is needed by some interrupt controllers to route MSI and MSI-X interrupts. The pci_get_vpd_ident() function is used to fetch a device's Vital Product Data (VPD) identifier string. If the device dev supports VPD and provides an identifier string, then *identptr is set to point at a read-only, null-terminated copy of the identifier string, and pci_get_vpd_ident() returns zero. If the device does not support VPD or does not provide an identifier string, then pci_get_vpd_ident() re- turns an error. The pci_get_vpd_readonly() function is used to fetch the value of a single VPD read-only keyword for the device dev. The keyword to fetch is identified by the two character string kw. If the device supports VPD and provides a read-only value for the requested keyword, then *vptr is set to point at a read-only, null-terminated copy of the value, and pci_get_vpd_readonly() returns zero. If the device does not support VPD or does not provide the requested keyword, then pci_get_vpd_readonly() returns an error. The pcie_get_max_completion_timeout() function returns the maximum com- pletion timeout configured for the device dev in microseconds. If the dev device is not a PCI-express device, pcie_get_max_completion_timeout() returns zero. When completion time- outs are disabled for dev, this function returns the maxmimum timeout that would be used if timeouts were enabled. The pcie_wait_for_pending_transactions() function waits for any pending transactions initiated by the dev device to complete. The function checks for pending transactions by polling the transactions pending flag in the PCI-express device status register. It returns true once the transaction pending flag is clear. If transactions are still pend- ing after max_delay milliseconds, pcie_wait_for_pending_transactions() returns false. If max_delay is set to zero, pcie_wait_for_pending_transactions() performs a single check; other- wise, this function may sleep while polling the transactions pending flag. pcie_wait_for_pending_transactions returns true if dev is not a PCI-express device. Device Configuration The pci_enable_busmaster() function enables PCI bus mastering for the device dev, by setting the PCIM_CMD_BUSMASTEREN bit in the PCIR_COMMAND register. The pci_disable_busmaster() function clears this bit. The pci_enable_io() function enables memory or I/O port address decod- ing for the device dev, by setting the PCIM_CMD_MEMEN or PCIM_CMD_PORTEN bit in the PCIR_COMMAND register appropriately. The pci_disable_io() function clears the appropriate bit. The space argu- ment specifies which resource is affected; this can be either SYS_RES_MEMORY or SYS_RES_IOPORT as appropriate. Device drivers should generally not use these routines directly. The PCI bus will enable de- coding automatically when a SYS_RES_MEMORY or SYS_RES_IOPORT resource is activated via bus_alloc_resource(9) or bus_activate_resource(9). The pci_get_max_payload() function returns the current maximum TLP pay- load size in bytes for a PCI-express device. If the dev device is not a PCI-express device, pci_get_max_payload() returns zero. The pci_get_max_read_req() function returns the current maximum read request size in bytes for a PCI-express device. If the dev device is not a PCI-express device, pci_get_max_read_req() returns zero. The pci_set_max_read_req() sets the PCI-express maximum read request size for dev. The requested size may be adjusted, and pci_set_max_read_req() returns the actual size set in bytes. If the dev device is not a PCI-express device, pci_set_max_read_req() returns zero. The pci_get_powerstate() function returns the current power state of the device dev. If the device does not support power management capa- bilities, then the default state of PCI_POWERSTATE_D0 is returned. The following power states are defined by PCI: PCI_POWERSTATE_D0 State in which device is on and running. It is receiving full power from the system and deliv- ering full functionality to the user. PCI_POWERSTATE_D1 Class-specific low-power state in which device context may or may not be lost. Buses in this state cannot do anything to the bus, to force devices to lose context. PCI_POWERSTATE_D2 Class-specific low-power state in which device context may or may not be lost. Attains greater power savings than PCI_POWERSTATE_D1. Buses in this state can cause devices to lose some context. Devices must be prepared for the bus to be in this state or higher. PCI_POWERSTATE_D3_HOT State in which the device is off and not run- ning. Device context is lost, and power from the device can be (but is not necessarily) re- moved. PCI_POWERSTATE_D3_COLD Same as PCI_POWERSTATE_D3_HOT, except power has been removed from the device. PCI_POWERSTATE_UNKNOWN State of the device is unknown. The pci_set_powerstate() function is used to transition the device dev to the PCI power state state. If the device does not support power management capabilities or it does not support the specific power state state, then the function will fail with EOPNOTSUPP. The pci_clear_pme() function is used to clear any pending PME# signal and disable generation of power management events. The pci_enable_pme() function is used to enable generation of power management events before suspending a device. The pci_iov_attach() function is used to advertise that the given de- vice (and associated device driver) supports PCI Single-Root I/O Virtu- alization (SR-IOV). A driver that supports SR-IOV must implement the PCI_IOV_INIT(9), PCI_IOV_ADD_VF(9) and PCI_IOV_UNINIT(9) methods. This function should be called during the DEVICE_ATTACH(9) method. If this function returns an error, it is recommended that the device driver still successfully attaches, but runs with SR-IOV disabled. The pf_schema and vf_schema parameters are used to define what device-spe- cific configuration parameters the device driver accepts when SR-IOV is enabled for the Physical Function (PF) and for individual Virtual Func- tions (VFs) respectively. See pci_iov_schema(9) for details on how to construct the schema. If either the pf_schema or vf_schema is invalid or specifies parameter names that conflict with parameter names that are already in use, pci_iov_attach() will return an error and SR-IOV will not be available on the PF device. If a driver does not accept configuration parameters for either the PF device or the VF devices, the driver must pass an empty schema for that device. The SR-IOV in- frastructure takes ownership of the pf_schema and vf_schema and is re- sponsible for freeing them. The driver must never free the schemas it- self. The pci_iov_attach_name() function is a variant of pci_iov_attach() that allows the name of the associated character device in /dev/iov to be specified by fmt. The pci_iov_attach() function uses the name of dev as the device name. The pci_iov_detach() function is used to advise the SR-IOV infrastruc- ture that the driver for the given device is attempting to detach and that all SR-IOV resources for the device must be released. This func- tion must be called during the DEVICE_DETACH(9) method if pci_iov_attach() was successfully called on the device and pci_iov_detach() has not subsequently been called on the device and re- turned no error. If this function returns an error, the DEVICE_DETACH(9) method must fail and return an error, as detaching the PF driver while VF devices are active would cause system instability. This function is safe to call and will always succeed if pci_iov_attach() previously failed with an error on the given device, or if pci_iov_attach() was never called on the device. The pci_save_state() and pci_restore_state() functions can be used by a device driver to save and restore standard PCI config registers. The pci_save_state() function must be invoked while the device has valid state before pci_restore_state() can be used. If the device is not in the fully-powered state (PCI_POWERSTATE_D0) when pci_restore_state() is invoked, then the device will be transitioned to PCI_POWERSTATE_D0 be- fore any config registers are restored. The pcie_flr() function requests a Function Level Reset (FLR) of dev. If dev is not a PCI-express device or does not support Function Level Resets via the PCI-express device control register, false is returned. Pending transactions are drained by disabling busmastering and calling pcie_wait_for_pending_transactions() before resetting the device. The max_delay argument specifies the maximum timeout to wait for pending transactions as described for pcie_wait_for_pending_transactions(). If pcie_wait_for_pending_transactions() fails with a timeout and force is false, busmastering is re-enabled and false is returned. If pcie_wait_for_pending_transactions() fails with a timeout and force is true, the device is reset despite the timeout. After the reset has been requested, pcie_flr sleeps for at least 100 milliseconds before returning true. Note that pcie_flr does not save and restore any state around the reset. The caller should save and restore state as needed. Message Signaled Interrupts Message Signaled Interrupts (MSI) and Enhanced Message Signaled Inter- rupts (MSI-X) are PCI capabilities that provide an alternate method for PCI devices to signal interrupts. The legacy INTx interrupt is avail- able to PCI devices as a SYS_RES_IRQ resource with a resource ID of zero. MSI and MSI-X interrupts are available to PCI devices as one or more SYS_RES_IRQ resources with resource IDs greater than zero. A dri- ver must ask the PCI bus to allocate MSI or MSI-X interrupts using pci_alloc_msi() or pci_alloc_msix() before it can use MSI or MSI-X SYS_RES_IRQ resources. A driver is not allowed to use the legacy INTx SYS_RES_IRQ resource if MSI or MSI-X interrupts have been allocated, and attempts to allocate MSI or MSI-X interrupts will fail if the dri- ver is currently using the legacy INTx SYS_RES_IRQ resource. A driver is only allowed to use either MSI or MSI-X, but not both. The pci_msi_count() function returns the maximum number of MSI messages supported by the device dev. If the device does not support MSI, then pci_msi_count() returns zero. The pci_alloc_msi() function attempts to allocate *count MSI messages for the device dev. The pci_alloc_msi() function may allocate fewer messages than requested for various reasons including requests for more messages than the device dev supports, or if the system has a shortage of available MSI messages. On success, *count is set to the number of messages allocated and pci_alloc_msi() returns zero. The SYS_RES_IRQ resources for the allocated messages will be available at consecutive resource IDs beginning with one. If pci_alloc_msi() is not able to al- locate any messages, it returns an error. Note that MSI only supports message counts that are powers of two; requests to allocate a non-power of two count of messages will fail. The pci_release_msi() function is used to release any allocated MSI or MSI-X messages back to the system. If any MSI or MSI-X SYS_RES_IRQ re- sources are allocated by the driver or have a configured interrupt han- dler, this function will fail with EBUSY. The pci_release_msi() func- tion returns zero on success and an error on failure. The pci_msix_count() function returns the maximum number of MSI-X mes- sages supported by the device dev. If the device does not support MSI- X, then pci_msix_count() returns zero. The pci_msix_pba_bar() function returns the offset in configuration space of the Base Address Register (BAR) containing the MSI-X Pending Bit Array (PBA) for device dev. The returned value can be used as the resource ID with bus_alloc_resource(9) and bus_release_resource(9) to allocate the BAR. If the device does not support MSI-X, then pci_msix_pba_bar() returns -1. The pci_msix_table_bar() function returns the offset in configuration space of the BAR containing the MSI-X vector table for device dev. The returned value can be used as the resource ID with bus_alloc_resource(9) and bus_release_resource(9) to allocate the BAR. If the device does not support MSI-X, then pci_msix_table_bar() returns -1. The pci_alloc_msix() function attempts to allocate *count MSI-X mes- sages for the device dev. The pci_alloc_msix() function may allocate fewer messages than requested for various reasons including requests for more messages than the device dev supports, or if the system has a shortage of available MSI-X messages. On success, *count is set to the number of messages allocated and pci_alloc_msix() returns zero. For MSI-X messages, the resource ID for each SYS_RES_IRQ resource identi- fies the index in the MSI-X table of the corresponding message. A re- source ID of one maps to the first index of the MSI-X table; a resource ID two identifies the second index in the table, etc. The pci_alloc_msix() function assigns the *count messages allocated to the first *count table indices. If pci_alloc_msix() is not able to allo- cate any messages, it returns an error. Unlike MSI, MSI-X does not re- quire message counts that are powers of two. The BARs containing the MSI-X vector table and PBA must be allocated via bus_alloc_resource(9) before calling pci_alloc_msix() and must not be released until after calling pci_release_msi(). Note that the vec- tor table and PBA may be stored in the same BAR or in different BARs. The pci_pending_msix() function examines the dev device's PBA to deter- mine the pending status of the MSI-X message at table index index. If the indicated message is pending, this function returns a non-zero value; otherwise, it returns zero. Passing an invalid index to this function will result in undefined behavior. As mentioned in the description of pci_alloc_msix(), MSI-X messages are initially assigned to the first N table entries. A driver may use a different distribution of available messages to table entries via the pci_remap_msix() function. Note that this function must be called af- ter a successful call to pci_alloc_msix() but before any of the SYS_RES_IRQ resources are allocated. The pci_remap_msix() function re- turns zero on success, or an error on failure. The vectors array should contain count message vectors. The array maps directly to the MSI-X table in that the first entry in the array speci- fies the message used for the first entry in the MSI-X table, the sec- ond entry in the array corresponds to the second entry in the MSI-X ta- ble, etc. The vector value in each array index can either be zero to indicate that no message should be assigned to the corresponding MSI-X table entry, or it can be a number from one to N (where N is the count returned from the previous call to pci_alloc_msix()) to indicate which of the allocated messages should be assigned to the corresponding MSI-X table entry. If pci_remap_msix() succeeds, each MSI-X table entry with a non-zero vector will have an associated SYS_RES_IRQ resource whose resource ID corresponds to the table index as described above for pci_alloc_msix(). MSI-X table entries that with a vector of zero will not have an associ- ated SYS_RES_IRQ resource. Additionally, if any of the original mes- sages allocated by pci_alloc_msix() are not used in the new distribu- tion of messages in the MSI-X table, they will be released automati- cally. Note that if a driver wishes to use fewer messages than were allocated by pci_alloc_msix(), the driver must use a single, contiguous range of messages beginning with one in the new distribution. The pci_remap_msix() function will fail if this condition is not met. Device Events The pci_add_device event handler is invoked every time a new PCI device is added to the system. This includes the creation of Virtual Func- tions via SR-IOV. The pci_delete_device event handler is invoked every time a PCI device is removed from the system. Both event handlers pass the device_t object of the relevant PCI device as dev to each callback function. Both event handlers are invoked while dev is unattached but with valid instance variables. SEE ALSO pci(4), pciconf(8), bus_alloc_resource(9), bus_dma(9), bus_release_resource(9), bus_setup_intr(9), bus_teardown_intr(9), devclass(9), device(9), driver(9), eventhandler(9), rman(9) "NewBus", FreeBSD Developers' Handbook, https://docs.freebsd.org/en/books/developers-handbook/. Shanley and Anderson, PCI System Architecture, Addison-Wesley, 2nd Edition, ISBN 0-201-30974-2. AUTHORS This manual page was written by Bruce M Simpson <bms@FreeBSD.org> and John Baldwin <jhb@FreeBSD.org>. BUGS The kernel PCI code has a number of references to "slot numbers". These do not refer to the geographic location of PCI devices, but to the device number assigned by the combination of the PCI IDSEL mecha- nism and the platform firmware. This should be taken note of when working with the kernel PCI code. The PCI bus driver should allocate the MSI-X vector table and PBA in- ternally as necessary rather than requiring the caller to do so. FreeBSD 15.0 March 27, 2025 PCI(9)
NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | AUTHORS | BUGS
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