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FILES.CONF(5) File Formats Manual FILES.CONF(5)

files.confrules base for the config utility

The various files.* files located in the kernel source tree contain all the necessary information needed by config(8) to parse a kernel configuration file and determine the list of files to compile.

The files.* rules base are simple, human-readable, text files. Empty lines, as well as text prefixed by the ‘#’ character, are ignored.

The OpenBSD kernel “sees” the various devices as a hierarchical tree, where the various devices “attach” to parent entities, which can either be physical devices themselves (such as a computer bus), or logical entities, designed to make the driver code simpler. Usually, the top-most devices are attached to the pseudo-device “mainbus”, which is itself reported as attached to a fictitious “root” node. There is no restriction on the “children” a device node may have; some device drivers can attach themselves to different kinds of parent devices. For example, the logical scsibus(4) device can either attach at a SCSI controller device, or at the logical atapiscsi(4) bus.

Some device attachments need to provide attachment information. For example, an isa(4) device will use a range of I/O ports, one or more DMA channels, and one interrupt vector. This attachment information is known as the “locators” for the device. Most of the buses support default values for unspecified locators, for devices that either do not require them (such as isa(4) cards not using interrupts), or which can autoconfigure themselves (such as pci(4) devices).

Attachment lines in the kernel configuration file must match the locators of the device they are attaching to. For example:

define pci {[dev = -1], [function = -1]}

With the rule above, the following kernel configuration lines are valid:

pciknob0 at pci? dev 2 function 42 # use fixed values
pciknob* at pci? dev ? function ?  # use default values
pciknob* at pci?                   # use default locators

But the following are not:

pciknob* at pci? trick ? treat ?               # unknown locators
pciknob* at pci? dev ? function ? usefulness ? # unknown locators

The following syntax defines a simple attribute, which can be later used to factorize code dependencies:

define attribute

An attachment-like attribute will also require locators to be specified. If no locators are necessary:

define attribute {}

If locators are provided:

define attribute {[locator1 = default1], [locator2 = default2]}

For simple device attachment, the following syntax defines a simple device, with no locators:

device devicename {}

If locators are necessary, they are specified as:

device devicename {[locator1 = default1], [locator2 = default2]}

A device can also reference an attribute with locators. This is in fact a dependency rule. For example, sys/conf/files defines the following attribute for SCSI controllers:

define scsi {} # no locators

And SCSI drivers can then be defined as:

device scsictrl: scsi

A device may depend on as many attributes as necessary:

device complexdev: simpledev, otherdev, specialattribute

Pseudo devices are defined as regular devices, except that they do not need locators, and use a different keyword:

pseudo-device loop: inet
pseudo-device ksyms

The rules above define, respectively, the loopback network interface and the kernel symbols pseudo-device.

Due to the tree structure of the device nodes, every device but the pseudo devices need to attach to some parent node. A device driver has to specify to which parents it can attach, with the following syntax:

attach device at parent, parent2, parent3

The rule above lists all the parent attributes a device may attach to. For example, given the following:

device smartknob: bells, whistles
attach smartknob at brainbus

The following configuration line is then valid:

smartknob* at brainbus?

Whilst the following is not:

smartknob* at dumbbus?

If a device supports attachments to multiple parents, using different “glue” routines every time, the following syntax specifies the details:

attach device at parent with device_parent_glue
attach device at parent2 with device_parent2_glue

This will define more required attributes, depending on the kernel configuration file's contents.

It is possible to include other rules files anywhere in a file, using the “include” keyword:

include "dev/pci/files.pci"

The above rule will include the rules for machine-independent PCI code.

The files sys/arch/machine/conf/files.machine, for every “machine” listed in the machine line in the kernel configuration file, as well as sys/conf/files, are always processed, and do not need to be included.

The kernel configuration file description passed to config(8) lists several compilation options, as well as several device definitions. From this list, config(8) will build a list of required attributes, which are:

Kernel source files are defined as:

file file-list	dependencies	need-rules

“file-list” typically only specifies a single filename. If instead it contains a list of filenames separated by the ‘|’ character, config(8) will select the first file from the list which exists. If “${MACHINE_ARCH}” or “${MACHINE}” is found in the filename, it will be substituted with the relevant base architecture name.

If the “dependencies” part is empty, the file will always be compiled in. This is the case for the core kernel files. Otherwise, the file will only be added to the list if the dependencies are met. Dependencies are based upon attributes and device names. Multiple dependencies can be written using the “|” and “&” operators. For example:

file netinet/ipsec_input.c (inet | inet6) & ipsec

The above rule teaches config(8) to only add sys/netinet/ipsec_input.c to the filelist if the “ipsec” attribute, and at least one of the “inet” and “inet6” attributes, are required.

The “need” rules can be empty, or one of the following keywords:

Create an attribute header file, defining whether or not this attribute is compiled in.
Create an attribute header file, defining how many instances of this attribute are to be compiled in. This rule is mostly used for pseudo-devices.

The “attribute header files” are simple C header files created in the kernel compilation directory, with the name attribute.h and containing the following line:

#define NATTRIBUTE 0

This would substitute the attribute name and its uppercase form, prefixed with the letter “N”, to “attribute” and “NATTRIBUTE”, respectively. For a “needs-flag” rule, the value on the “#define” line is either 1 if the attribute is required, or 0 if it is not required. For a “needs-count” rule, the value is the number of device instances required, or 0 if the device is not required.

Attribute files are created for every attribute listed with a “need” rule, even if it is never referenced from the kernel configuration file.

sys/arch/machine/conf/files.machine must also supply the following special commands:

Defines how many partitions are available on disk block devices, usually 16. This value is used by config(8) to set up various device information structures.
Defines the bounds, and the default value, for the “maxusers” parameter in the kernel configuration file. The usual values are 2 8 64 ; config(8) will report an error if the “maxusers parameter” in the kernel configuration file does not fit in the specified range.

Rules for architecture-dependent files, for the “machine” architecture.
Rules for the “class” class of devices.
Rules for the common SCSI subsystem.


March 2, 2016 OpenBSD-6.7