CONFIG(9) BSD Kernel Developer's Manual CONFIG(9)NAMEconfig — the autoconfiguration framework “device definition” language
DESCRIPTION
In NetBSD, the config(1) program reads and verifies a machine description
file (documented in config(5)) that specifies the devices to include in
the kernel. A table is produced by config(1) which is used by the kernel
during autoconfiguration (see autoconf(9)) giving needed hints and
details on matching hardware devices with device drivers.
Each device in the machine description file has:
A Name The name is simply an alphanumeric string that ends in a unit
number (e.g., "sd0", "sd1", and so forth). These unit numbers
identify particular instances of a base device name; the base
name in turn maps directly to a device driver. Device unit num‐
bers are independent of hardware features.
A Parent
Every device must have a parent. The pairing is denoted by
"child at parent". These pairings form the links in a directed
graph. The root device is the only exception, as it does not
have a parent.
Locators
Locators are used to augment the parent/child pairings that
locate specific devices. Each locator value is simply an integer
that represents some sort of device address on the parent bus or
controller. This can be a memory address, an I/O port, a driver
number, or any other value. Locators can sometimes be wildcarded
on devices that support direct connection.
Attributes
An attribute describes the device's relationship with the code;
it then serves to constrain the device graph. A plain attribute
describes some attribute of a device. An interface attribute
describes a kind of “software interface” and declares the
device's ability to support other devices that use that inter‐
face. In addition, an interface attribute usually identifies
additional locators.
During autoconfiguration, the directed graph is turned into a tree by
nominating one device as the root node and matching drivers with devices
by doing a depth-first traversal through the graph starting at this root
node.
However, there must be constraints on the parent/child pairings that are
possible. These constraints are embedded in the “device definition”
files. The remainder of this page describes the “device definition” lan‐
guage and how to use this language to add new functionality to the NetBSD
kernel.
DEVICE DEFINITION FILES
The device definition files are separated into machine-dependent and
machine-independent files. The machine-dependent file is located in
sys/arch/<arch>/conf/files.<arch>, where <arch> is the name of NetBSD
architecture. The machine-independent file is located in sys/conf/files.
It in turn includes files for the machine-independent drivers located in
sys/dev/<bus>/files.<bus>, where <bus> is the name of the machine-inde‐
pendent bus.
These files define all legal devices and pseudo-devices. They also
define all attributes and interfaces, establishing the rules that deter‐
mine allowable machine descriptions, and list the source files that make
up the kernel.
Each device definition file consists of a list of statements, typically
one per line. Comments may be inserted anywhere using the “#” character,
and any line that begins with white space continues the previous line.
Valid statements are:
cinclude filename
Conditionally include contents of file filename to currently pro‐
cessed configuration. If the specified filename doesn't exist, a
warning is printed, but the error ignored.
defflag [filename] {options}
The space-separated list of pre-processor macros options are
defined in file filename. This statement permits ``options FOO''
for FOO (i.e, without a value) in the machine description file.
config(1) will generate an error if a value is given. If the
filename field is not specified, it will be constructed based
upon the lower-case of the option name, ``opt_foo.h'' for exam‐
ple. The option is case-sensitive.
defparam [filename] {options}
The space-separated list of pre-processor macros options are
defined in file filename. This statement permits ``options
FOO=bar'' or ``option FOO="\"com\""'' in the machine description
file. config(1) will generate an error if a value is not given.
If the filename field is not specified, it will be constructed
based upon the lower-case of the option name, ``opt_foo.h'' for
example. The option is case-sensitive.
defopt [filename] {options}
The space-separated list of pre-processor macros options are
defined in file filename. This statement permits the syntax of
either the defflag and defparam statements and config(1) does not
perform any checking of whether ``options FOO'' takes a value.
Therefore, the use of the defopt statement is deprecated in
favour of the defflag and defparam statements. If the filename
field is not specified, it will be constructed based upon the
lower-case of the option name, ``opt_foo.h'' for example. The
option is case-sensitive.
deffs name [[name] ...]
Define a filesystem name.
devclass name
Define a device class name. A device class is similar to an
attribute.
define name [{locators}]
The attribute name is defined and device definitions can then
refer to it. If the attribute is an interface attribute and
defines optional locators, device attributes that refer to name
are assumed to share the interface and require the same locators.
device name [{locators}]: [attributes]
The device name is defined and requires the optional comma-sepa‐
rated list of locators locators. The optional attributes define
attribute dependencies.
attach name at interface [with ifname]: [attributes]
The device name is defined and supports the interface interface.
If ifname is specified, it is used to specify the interface to
the driver for device name (see driver(9) for details). The
optional attributes define attribute dependencies.
defpseudo name: [{locators}]
The pseudo-device name is defined. The optional locators may be
defined, but are largely pointless since no device can attach to
a pseudo-device.
file pathname [attributes [flags]] [rule]
The file pathname is added to the list of files used to build the
kernel. If no attributes are specified, the file is always added
to the kernel compilation. If any of the attributes are speci‐
fied by other devices in the machine description file, then the
file is included in compilation, otherwise it is omitted. Valid
values for the optional flags are:
needs-count
Specify that config should generate a file for each of
the attributes notifying the driver how many of some par‐
ticular device or set of devices are configured in the
kernel. This flag allows drivers to make calculations of
driver used at compile time. This option prevents auto‐
configuration cloning.
needs-flag
This flag performs the same operation as needs-count but
only records if the number is nonzero. Since the count
is not exact, needs-flag does not prevent autoconfigura‐
tion cloning.
device-major name char [block] [attributes]
The character device switch name associated with a character
major device number is added to the list of device switches used
to build the kernel. If block is specified, the block device
switch associated with a block major device number is also added.
If all of attributes are specified by devices in the machine
description files, then device switches are added into the device
switches' table of the kernel in compilation, otherwise they are
omitted.
include filename
Include contents of file filename to currently processed configu‐
ration. If the specified filename doesn't exist, config(1) exits
with error.
package filename
Changes prefix to directory of filename, processes contents of
filename, and switches back to previous prefix. This is syntac‐
tic sugar for:
prefix dirname(filename)
include basename(filename)
prefix
prefix [dirname]
If dirname is specified, it is pushed on top of prefix stack.
Any further files specified via option file would have the prefix
implicitly prepended before its filename. If dirname is not
specified, pops (removes) a prefix from prefix stack.
To allow locators to be wildcarded in the machine description file, their
default value must be defined in the attribute definition. To allow
locators to be omitted entirely in the machine description file, enclose
the locator in square brackets. This can be used when some locators do
not make sense for some devices, but the software interface requires
them.
CODE REFERENCES
The device definition files are in sys/conf/files,
sys/arch/<arch>/conf/files.<arch>, and sys/dev/<bus>/files.<bus>.
The grammar for machine description files can be found in config(1), in
usr.bin/config/gram.y.
SEE ALSOconfig(1), config(5), autoconf(9), driver(9)
Building 4.4 BSD Systems with Config.
Chris Torek, Device Configuration in 4.4BSD, 1992.
HISTORY
Autoconfiguration first appeared in 4.1BSD. The autoconfiguration frame‐
work was completely revised in 4.4BSD. It has been modified within
NetBSD to support bus-independent drivers and bus-dependent attachments.
BSD March 3, 2010 BSD
