1.\" $OpenBSD: pci_conf_read.9,v 1.13 2021/05/01 16:11:10 visa Exp $ 2.\" 3.\" Copyright (c) 2005 Michael Shalayeff 4.\" All rights reserved. 5.\" 6.\" Permission to use, copy, modify, and distribute this software for any 7.\" purpose with or without fee is hereby granted, provided that the above 8.\" copyright notice and this permission notice appear in all copies. 9.\" 10.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 11.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 12.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 13.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 14.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 15.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 16.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 17.\" 18.Dd $Mdocdate: May 1 2021 $ 19.Dt PCI_CONF_READ 9 20.Os 21.Sh NAME 22.Nm pci_make_tag , 23.Nm pci_decompose_tag , 24.Nm pci_conf_read , 25.Nm pci_conf_write 26.Nd PCI config space manipulation functions 27.Sh SYNOPSIS 28.In alpha/pci/pci_machdep.h 29.In i386/pci/pci_machdep.h 30.In powerpc/pci/pci_machdep.h 31.In machine/pci_machdep.h 32.Ft pcitag_t 33.Fn pci_make_tag "pci_chipset_tag_t pc" "int bus" "int dev" "int func" 34.Ft void 35.Fn pci_decompose_tag "pci_chipset_tag_t pc" "pcitag_t tag" "int *busp" \ 36"int *devp" "int *funcp" 37.Ft pcireg_t 38.Fn pci_conf_read "pci_chipset_tag_t pc" "pcitag_t tag" "int reg" 39.Ft void 40.Fn pci_conf_write "pci_chipset_tag_t pc" "pcitag_t tag" "int reg" \ 41"pcireg_t val" 42.Sh DESCRIPTION 43These functions provide a way to access PCI configuration space. 44.Pp 45The following types are defined in the machine dependent include file 46.In pci_machdep.h . 47.Pp 48.Bl -tag -width pci_chipset_tag_t -offset indent -compact 49.It pci_chipset_tag_t 50a PCI chipset descriptor; 51.It pcitag_t 52a PCI device tag; 53.It pcireg_t 54a PCI register datum. 55.El 56.Pp 57In order to access PCI configuration space, a device tag shall be made using 58.Nm pci_make_tag 59given the PCI chipset tag 60.Ar pc 61and the device specification in a tuple of 62.Ar bus , 63.Ar device , 64.Ar function . 65The PCI tag composition is a PCI chipset dependent operation 66although often as simple as a shift and logical OR combination. 67.Pp 68The 69.Nm pci_decompose_tag 70provides a reverse operation. 71Once a tag is composed, it is possible to perform configuration 72space read and write with 73.Nm pci_conf_read 74and 75.Nm pci_conf_write , 76respectively. 77Access to PCI configuration space is only provided for whole 78.Nm pcireg_t 79items, which is usually a 32-bit integer. 80Access to non-existent PCI devices do not (or should not) generate 81any kinds of faults or interruptions and thus allow for an easy device 82scanning by cycling through all possible device and function numbers 83for a given bus. 84.Pp 85Below is an overview of defined PCI configuration space registers for 86devices: 87.Bl -tag -width 0xff -offset indent 88.It 0x00 89Vendor (lower word) and Product (higher word) identification 90(see 91.Pa /sys/dev/pci/pcidevs 92for a comprehensive list). 93.It 0x04 94Commands and Status register. 95.It 0x08 96PCI device's class and subclass IDs. 97See 98.Pa /sys/dev/pci/pcireg.h 99for PCI_CLASS_* and PCI_SUBCLASS_* definitions. 100.It 0x0c 101Specify (low byte to high): cache line size, PCI latency timer, header type, 102and BIST. 103.It 0x10 - 0x28 104Base address registers for I/O and memory space mapped registers. 105.It 0x28 106CardBus CIS register. 107.It 0x2c 108Similar to 0x00 register's definitions for a subsystem identification. 109.It 0x34 110A pointer to the capabilities list. 111Each item is an offset in the configuration space itself. 112.It 0x3c 113Interrupt line and pin numbers. 114.El 115.Sh SEE ALSO 116.Xr cardbus 4 , 117.Xr pci 4 , 118.Xr pci_intr_map 9 119.Sh HISTORY 120These functions first appeared in 121.Ox 1.2 . 122.\" .Sh AUTHORS 123