CONFIG(9) NetBSD Kernel Manual CONFIG(9)
NAME
config - the autoconfiguration framework ``device definition'' language
DESCRIPTION
In NetBSD, the config(8) program reads and verifies a machine description file specifying the devices to include in the kernel. A table is pro- duced by config(8) 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 (eg. "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 the locate specific devices. Each locator value is simply an integer that represents some sort of device address on the parent bus or con- troller. This can be a memory address, and 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 de- scribes a kind of ``software interface'' and declares the de- vices's ability to support other devices that use that interface. 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'' language 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 ma- chine-independent files. The machine-dependent file is located in sys/arch/<arch>/conf/files.<arch>, where <arch> is the name of NetBSD ar- chitecture. 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 de- fine all attributes and interfaces, establishing the rules that determine 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 ``#'' charac- ter, and any line that begins with white space continues the previous line. Valid statements are: defflag [filename] {options} The space-separated list of pre-processor macros options are de- fined in file filename. This statement permits ``options FOO'' for FOO (i.e, without a value) in the machine description file. config(8) will generate an error if a value is given. If the filename field is not specified, the options are defined on the commandline invocation of make(1). The option is case-sensitive. defparam [filename] {options} The space-separated list of pre-processor macros options are de- fined in file filename. This statement permits ``options FOO=bar'' or ``option FOO="\"com\""'' in the machine description file. config(8) will generate an error if a value is not given. If the filename field is not specified, the options are defined on the commandline invocation of make(1). The option is case- sensitive. defopt [filename] {options} The space-separated list of pre-processor macros options are de- fined in file filename. This statement permits the syntax of ei- ther the defflag and defparam statements and config(8) 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, the options are defined on the command- line invocation of make(1). The option is case-sensitive. deffs [filename] name Define a filesystem name. devclass name Define a device class name. A device class is similar to an at- tribute. define name [{locators}] The attribute name is defined and device definitions can then re- fer to it. If the attribute is an interface attribute and de- fines 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 op- tional 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 descripton 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. major major-list The devices listed in major-list are associated with major device numbers, allowing them to be used for file system roots, swapping and crash dumps. Since major numbers are machine dependent, they should not appear in the machine-independent device definition files. To allow locators to be wildcarded in the machine description file, their default value must be defined in the attribute definition. To allow lo- cators 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
This section describes places within the NetBSD source tree where actual code implementing or utilising the autoconfiguration framework can be found. All pathnames are relative to /usr/src. 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(8), in usr.sbin/config/gram.y.
SEE ALSO
config(8), 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 NetB- SD to support bus-independent drivers and bus-dependent attachments. NetBSD 1.6 June 17, 2001 3
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