The pciconf utility provides a command line interface to functionality provided by the pci(4) ioctl(2) interface. As such, some of the functions are only available to users with write access to /dev/pci, normally only the super-user.
With the -l option, it lists all devices found by the boot probe in the following format:
foo0@pci0:4:0: class=0x010000 card=0x00000000 chip=0x000f1000 rev=0x01 hdr=0x00
bar0@pci0:5:0: class=0x000100 card=0x00000000 chip=0x88c15333 rev=0x00 hdr=0x00
none0@pci0:6:0: class=0x020000 card=0x00000000 chip=0x802910ec rev=0x00 hdr=0x00
If the -v option is supplied, pciconf will attempt to load the vendor/device information database, and print vendor, device, class and subclass identification strings for each device.
The first column gives the device name, unit number, and selector. If there is no device configured in the kernel for the PCI device in question, the device name will be "none". Unit numbers for unconfigured devices start at zero and are incremented for each unconfigured device that is encountered. The selector is in a form which may directly be used for the other forms of the command. The second column is the class code, with the class byte printed as two hex digits, followed by the sub-class and the interface bytes. The third column gives the contents of the subvendorid register, introduced in revision 2.1 of the PCI standard. It is 0 for most current (2.0) PCI cards, but is supposed to be loaded with a unique card identification code in newly developed PCI cards. The field consists of the card ID in the upper half and the card vendor ID in the lower half of the value.
The fourth column contains the chip device ID, which identifies the chip this card is based on. It consists of two fields, identifying the chip and its vendor, as above. The fifth column prints the chips revision. The sixth column describes the header type. Currently assigned header types are 0 for all devices except PCI to PCI bridges, and 1 for such bridge chips. If the most significant bit of the header type register is set for function 0 of a PCI device, it is a multi-function device, which contains several (similar or independent) functions on one chip.
All invocations of pciconf except for -l require a selector of the form pci bus : device (optionally followed by : function). A final colon may be appended and will be ignored; this is so that the first column in the output of pciconf -l can be used without modification. All numbers are base 10.
With the -a flag, pciconf determines whether any driver has been assigned to the device identified by selector. An exit status of zero indicates that the device has a driver; non-zero indicates that it does not.
The -r option reads a configuration space register at byte offset addr of device selector and prints out its value in hexadecimal. The optional second address addr2 specifies a range to read. The -w option writes the value into a configuration space register at byte offset addr of device selector. For both operations, the flags -b and -h select the width of the operation; -b indicates a byte operation, and -h indicates a halfword (two-byte) operation. The default is to read or write a longword (four bytes).
The PCI vendor/device information database is normally read from /usr/share/misc/pci_vendors. This path can be overridden by setting the environment variable PCICONF_VENDOR_DATABASE.