NAME
pci_make_tag,
pci_decompose_tag,
pci_conf_read,
pci_conf_write —
PCI config space manipulation
functions
SYNOPSIS
#include
<alpha/pci/pci_machdep.h>
#include
<i386/pci/pci_machdep.h>
#include
<powerpc/pci/pci_machdep.h>
#include
<machine/pci_machdep.h>
pcitag_t
pci_make_tag(pci_chipset_tag_t
pc, int bus,
int dev,
int func);
void
pci_decompose_tag(pci_chipset_tag_t
pc, pcitag_t tag,
int *busp,
int *devp,
int *funcp);
pcireg_t
pci_conf_read(pci_chipset_tag_t
pc, pcitag_t tag,
int reg);
void
pci_conf_write(pci_chipset_tag_t
pc, pcitag_t tag,
int reg,
pcireg_t val);
DESCRIPTION
These functions provide a way to access PCI configuration space.
The following types are defined in the machine dependent include
file <pci_machdep.h>.
- pci_chipset_tag_t
- a PCI chipset descriptor;
- pcitag_t
- a PCI device tag;
- pcireg_t
- a PCI register datum.
In order to access PCI configuration space, a device tag shall be
made using pci_make_tag given the PCI chipset tag
pc and the device specification in a tuple of
bus, device,
function. The PCI tag composition is a PCI chipset
dependent operation although often as simple as a shift and logical OR
combination.
The pci_decompose_tag provides a reverse
operation. Once a tag is composed, it is possible to perform configuration
space read and write with pci_conf_read and
pci_conf_write, respectively. Access to PCI
configuration space is only provided for whole
pcireg_t items, which is usually a 32-bit integer.
Access to non-existent PCI devices do not (or should not) generate any kinds
of faults or interruptions and thus allow for an easy device scanning by
cycling through all possible device and function numbers for a given
bus.
Below is an overview of defined PCI configuration space registers for devices:
- 0x00
- Vendor (lower word) and Product (higher word) identification (see /sys/dev/pci/pcidevs for a comprehensive list).
- 0x04
- Commands and Status register.
- 0x08
- PCI device's class and subclass IDs. See /sys/dev/pci/pcireg.h for PCI_CLASS_* and PCI_SUBCLASS_* definitions.
- 0x0c
- Specify (low byte to high): cache line size, PCI latency timer, header type, and BIST.
- 0x10 - 0x28
- Base address registers for I/O and memory space mapped registers.
- 0x28
- CardBus CIS register.
- 0x2c
- Similar to 0x00 register's definitions for a subsystem identification.
- 0x34
- A pointer to the capabilities list. Each item is an offset in the configuration space itself.
- 0x3c
- Interrupt line and pin numbers.
SEE ALSO
HISTORY
These functions first appeared in OpenBSD 1.2.