CONF(9) CONF(9)
NAME
conf - native and hosted kernel configuration file
DESCRIPTION
Plan 9 kernels are built for a given target platform using
platform-specific code in directory /sys/src/9/platform and
portable code in /sys/src/9/port, /sys/src/9/ip and else-
where. Existing platforms include alphapc for the DEC
Alpha, iPAQ for the Compaq iPAQ, pc for the Intel x86, and
ppc for the IBM/Motorola PowerPC. Each platform can have
several different kernels with different configurations. A
given configuration is built in the platform's directory
using the mk(1) command:
mk 'CONF=conf'
where conf is a text file that specifies drivers, protocols
and other parameters for that particular kernel: a parts
list. The result of a successful mk is an executable or
bootable file with a name determined by the platform's
mkfile, typically 9conf.
A kernel configuration file has several sections of the form
label
item [ subitem ... ]
...
Each section begins with a label at the start of a line,
which names a configuration category, followed by a list of
each item to select from that category, one line per item,
with white space (ie, blank or tab) at the start of the
line. An item line can optionally list one or more subitems
that must be included in the kernel to support it. A line
that starts with a `#' is a comment. Empty lines are
ignored.
Labels are chosen from the following set, listed in the
order in which they conventionally appear in a configuration
file:
dev Device drivers
ip IP protocols (native kernels only) taken from ../ip
link Hardware-specific parts of device drivers.
misc Architecture-specific files; specific VGA and SCSI
interfaces
lib Libraries to link with the kernel
port C code and declarations to include as-is in the
generated configuration file
boot Configuration for boot(8)
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CONF(9) CONF(9)
bootdir List of files and directories to put in the boot
directory of root(3).
When an item is listed under a given label it causes a cor-
responding component to be included in the kernel. The
details depend on the label, as discussed below. Each
subitem represents a kernel subcomponent required by the
corresponding item. Both items and subitems can be either
portable (platform-independent) or platform-specific. The
source file for a given item or subitem is sought in the
platform-directory (for platform-specific code), and in
directories ../port and ../ip, under control of the
platform's mkfile and ../port/portmkfile (which is included
by mkfile). Resulting object files are left in the platform
directory.
Outside the dev section, each item and subitem x causes the
kernel image to include the code compiled from x.c, (or x.s
for assembly-language support), or portdir/x.c, where
portdir is one of the portable directories mentioned above.
In the dev section, an item x corresponds instead to the
driver source file devx.c in the current (platform-specific)
directory or a portable driver portdir/devx.c. Subitems are
handled as in any other section. Typically they are auxil-
iary files that are needed by the associated driver.
For instance, in a native kernel the portable driver for the
draw device uses platform-specific code from screen.c. That
can be represented as follows:
dev
draw screen
Each item x in the ip section corresponds to a protocol
implementation compiled from ../ip/x.c. Any subitems are
dealt with in the same way as in the dev section.
The link section provides a way for hardware-specific parts
of drivers to link at runtime to the hardware-invariant part
of a device drivers. For each item x, the kernel will call
the function xlink during its initialisation. Typically
that function makes itself known to the device driver by
calling a function provided by that driver, passing the
address of a interface-specific data structure or linkage
table. For example, ethersmc is an interface-specific com-
ponent:
link
...
ethersmc
and its source file ethersmc.c provides a function
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CONF(9) CONF(9)
ethersmclink that calls addethercard in the interface-
invariant part of the driver, devether.c:
void
ethersmclink(void)
{
addethercard("smc91cXX", reset);
}
The boot section configures boot(8), the first user program
run by the kernel. Each line in the section names a possi-
ble boot method (see boot(8) for the current list). The
first will be the default. Also by default, /boot will run
/bin/termrc from cpurc(8), with bootdisk set to #S/sdC0/.
To change the defaults, the line (or lines) containing a
boot label can be given some options:
boot cpu
The kernel is a cpu server: run /bin/cpurc not
/bin/termrc (see cpurc(8)).
boot cpu boot disk
Use disk as the default bootdisk.
The lib section lists the libraries to include when linking
the kernel, in an order that satisfies any dependencies
amongst them. Each item x corresponds to /$objtype/libx.a,
a target-specific library produced by compiling the C source
code in /sys/src/libitem, where objtype is set in the
platform's mkfile to the target system's object type (eg,
386, power, etc).
An item in the bootdir section has one of the forms:
name
source name
where name and source are path names (often absolute path
names). The kernel's initial root file system (see root(3))
will contain a file or directory with the given name. The
contents will come from the file name (which must exist)
unless an explicit source file is given.
The port section usually contains initialisations for
kernel-specific values. The most common one is
int cpuserver = n;
where n is non-zero for cpu servers and file servers, and
zero otherwise.
FILES
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CONF(9) CONF(9)
/sys/src/9/port/mkdevc
/sys/src/9/port/mkdevlist
/sys/src/9/port/mkroot
SEE ALSO
mk(1)
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