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.Dd $Mdocdate: March 2 2016 $
.Dt FILES.CONF 5
.Os
.Sh NAME
.Nm files.conf
.Nd rules base for the config utility
.Sh DESCRIPTION
The various
.Pa files.*\&
files located in the kernel source tree
contain all the necessary information needed by
.Xr config 8
to parse a kernel configuration file and determine the list of files to
compile.
.Pp
The
.Pa files.*\&
rules base are simple, human-readable, text files.
Empty lines, as well as text prefixed by the
.Sq #
character, are ignored.
.Sh DEVICE TREE CONCEPT
The
.Ox
kernel
.Dq sees
the various devices as a hierarchical tree, where the various devices
.Dq attach
to parent entities, which can either be physical devices themselves
.Pq 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
.Dq mainbus ,
which is itself reported as attached to a fictitious
.Dq root
node.
There is no restriction on the
.Dq children
a device node may have;
some device drivers can attach themselves to different kinds of parent devices.
For example, the logical
.Xr scsibus 4
device can either attach at a SCSI controller device,
or at the logical
.Xr atapiscsi 4
bus.
.Sh LOCATORS
Some device attachments need to provide attachment information.
For example, an
.Xr 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
.Dq locators
for the device.
Most of the buses support default values for unspecified locators, for devices
that either do not require them
.Po
such as
.Xr isa 4
cards not using interrupts
.Pc ,
or which can autoconfigure themselves
.Po
such as
.Xr pci 4
devices
.Pc .
.Pp
Attachment lines in the kernel configuration file must match the locators of
the device they are attaching to.
For example:
.Bd -literal -offset indent
define pci {[dev = -1], [function = -1]}
.Ed
.Pp
With the rule above,
the following kernel configuration lines are valid:
.Bd -literal -offset indent
pciknob0 at pci? dev 2 function 42 # use fixed values
pciknob* at pci? dev ? function ?  # use default values
pciknob* at pci?                   # use default locators
.Ed
.Pp
But the following are not:
.Bd -literal -offset indent
pciknob* at pci? trick ? treat ?               # unknown locators
pciknob* at pci? dev ? function ? usefulness ? # unknown locators
.Ed
.Sh ATTRIBUTES
The following syntax defines a simple attribute,
which can be later used to factorize code dependencies:
.Pp
.Dl define attribute
.Pp
An attachment-like attribute will also require locators to be specified.
If no locators are necessary:
.Pp
.Dl define attribute {}
.Pp
If locators are provided:
.Pp
.Dl define attribute {[locator1 = default1], [locator2 = default2]}
.Sh DEVICES
For simple device attachment, the following syntax
defines a simple device, with no locators:
.Pp
.Dl device devicename {}
.Pp
If locators are necessary, they are specified as:
.Pp
.Dl device devicename {[locator1 = default1], [locator2 = default2]}
.Pp
A device can also reference an attribute with locators.
This is in fact a dependency rule.
For example,
.Pa sys/conf/files
defines the following attribute for SCSI controllers:
.Pp
.Dl define scsi {}			# no locators
.Pp
And SCSI drivers can then be defined as:
.Pp
.Dl device scsictrl: scsi
.Pp
A device may depend on as many attributes as necessary:
.Pp
.Dl device complexdev: simpledev, otherdev, specialattribute
.Sh PSEUDO DEVICES
Pseudo devices are defined as regular devices, except that they do not
need locators, and use a different keyword:
.Bd -literal -offset indent
pseudo-device loop: inet
pseudo-device ksyms
.Ed
.Pp
The rules above define, respectively,
the loopback network interface and the kernel symbols pseudo-device.
.Sh DEVICE ATTACHMENT RULES
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:
.Pp
.Dl attach device at parent, parent2, parent3
.Pp
The rule above lists all the parent attributes a device may attach to.
For example, given the following:
.Bd -literal -offset indent
device smartknob: bells, whistles
attach smartknob at brainbus
.Ed
.Pp
The following configuration line is then valid:
.Pp
.Dl smartknob* at brainbus?
.Pp
Whilst the following is not:
.Pp
.Dl smartknob* at dumbbus?
.Pp
If a device supports attachments to multiple parents, using different
.Dq glue
routines every time, the following syntax specifies the details:
.Bd -literal -offset indent
attach device at parent with device_parent_glue
attach device at parent2 with device_parent2_glue
.Ed
.Pp
This will define more required attributes, depending on the kernel
configuration file's contents.
.Sh RULE FILE INCLUSION
It is possible to include other rules files anywhere in a file, using the
.Dq include
keyword:
.Pp
.Dl include \&"dev/pci/files.pci\&"
.Pp
The above rule will include the rules for machine-independent PCI code.
.Pp
The files
.Pa sys/arch/machine/conf/files.machine ,
for every
.Dq machine
listed in the machine line in the kernel configuration file, as well as
.Pa sys/conf/files ,
are always processed, and do not need to be included.
.Sh ATTRIBUTE REQUIREMENTS
The kernel configuration file description passed to
.Xr config 8
lists several compilation options, as well as several device definitions.
From this list,
.Xr config 8
will build a list of required attributes, which are:
.Pp
.Bl -bullet -offset indent -compact
.It
The
.Dq option
lines, with the option name translated to lowercase (for example, an
.Dq option INET6
line will produce the
.Dq inet6
attribute).
.It
The device and pseudo-device names, except for
.Dq root .
.El
.Sh KERNEL FILE LIST
Kernel source files are defined as:
.Bd -literal -offset indent
file file-list	dependencies	need-rules
.Ed
.Pp
.Dq file-list
typically only specifies a single filename.
If instead it contains a list of filenames separated by the
.Sq \&|
character,
.Xr config 8
will select the first file from the list which exists.
If
.Dq ${MACHINE_ARCH}
or
.Dq ${MACHINE}
is found in the filename, it will be substituted with the
relevant base architecture name.
.Pp
If the
.Dq 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
.Dq \&|
and
.Dq &
operators.
For example:
.Pp
.Dl file netinet/ipsec_input.c	(inet | inet6) & ipsec
.Pp
The above rule teaches
.Xr config 8
to only add
.Pa sys/netinet/ipsec_input.c
to the filelist if the
.Dq ipsec
attribute, and at least one of the
.Dq inet
and
.Dq inet6
attributes, are required.
.Pp
The
.Dq need
rules can be empty, or one of the following keywords:
.Pp
.Bl -tag -width "needs-count" -compact
.It Ar needs-flag
Create an attribute header file, defining whether or not this
attribute is compiled in.
.It Ar needs-count
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.
.El
.Pp
The
.Dq attribute header files
are simple C header files created in the kernel compilation directory,
with the name
.Pa attribute.h
and containing the following line:
.Pp
.Dl #define NATTRIBUTE	0
.Pp
This would substitute the attribute name and its uppercase form, prefixed with
the letter
.Dq N ,
to
.Dq attribute
and
.Dq NATTRIBUTE ,
respectively.
For a
.Dq needs-flag
rule, the value on the
.Dq #define
line is either 1 if the attribute is required, or 0 if it is not required.
For a
.Dq needs-count
rule, the value is the number of device instances required, or 0
if the device is not required.
.Pp
Attribute files are created for every attribute listed with a
.Dq need
rule, even if it is never referenced from the kernel configuration file.
.Sh MISCELLANEOUS ITEMS
.Pa sys/arch/machine/conf/files.machine
must also supply the following special commands:
.Bl -tag -width maxpartitions
.It Ar maxpartitions
Defines how many partitions are available on disk block devices, usually 16.
This value is used by
.Xr config 8
to set up various device information structures.
.It Ar maxusers
Defines the bounds, and the default value, for the
.Dq maxusers
parameter in the kernel configuration file.
The usual values are 2 8 64 ;
.Xr config 8
will report an error if the
.Dq maxusers parameter
in the kernel configuration file does not fit in the specified range.
.El
.Sh FILES
.Bl -tag -width Ds
.It Pa sys/arch/machine/conf/files.machine
Rules for architecture-dependent files, for the
.Dq machine
architecture.
.It Pa sys/dev/class/files.class
Rules for the
.Dq class
class of devices.
.It Pa sys/scsi/files.scsi
Rules for the common SCSI subsystem.
.El
.Sh SEE ALSO
.Xr config 8