drivers/base/Kconfig v3.0-rc7


Menu: Generic Driver Options

UEVENT_HELPER_PATH

path to uevent helper

Path to uevent helper program forked by the kernel for
every uevent.
Before the switch to the netlink-based uevent source, this was
used to hook hotplug scripts into kernel device events. It
usually pointed to a shell script at /sbin/hotplug.
This should not be used today, because usual systems create
many events at bootup or device discovery in a very short time
frame. One forked process per event can create so many processes
that it creates a high system load, or on smaller systems
it is known to create out-of-memory situations during bootup.

DEVTMPFS

Maintain a devtmpfs filesystem to mount at /dev

This creates a tmpfs/ramfs filesystem instance early at bootup.
In this filesystem, the kernel driver core maintains device
nodes with their default names and permissions for all
registered devices with an assigned major/minor number.
Userspace can modify the filesystem content as needed, add
symlinks, and apply needed permissions.
It provides a fully functional /dev directory, where usually
udev runs on top, managing permissions and adding meaningful
symlinks.
In very limited environments, it may provide a sufficient
functional /dev without any further help. It also allows simple
rescue systems, and reliably handles dynamic major/minor numbers.

Notice: if CONFIG_TMPFS isn't enabled, the simpler ramfs
file system will be used instead.

DEVTMPFS_MOUNT

Automount devtmpfs at /dev, after the kernel mounted the rootfs

This will instruct the kernel to automatically mount the
devtmpfs filesystem at /dev, directly after the kernel has
mounted the root filesystem. The behavior can be overridden
with the commandline parameter: devtmpfs.mount=0|1.
This option does not affect initramfs based booting, here
the devtmpfs filesystem always needs to be mounted manually
after the roots is mounted.
With this option enabled, it allows to bring up a system in
rescue mode with init=/bin/sh, even when the /dev directory
on the rootfs is completely empty.

STANDALONE

Select only drivers that don't need compile-time external firmware

Select this option if you don't have magic firmware for drivers that
need it.

If unsure, say Y.

PREVENT_FIRMWARE_BUILD

Prevent firmware from being built

Say yes to avoid building firmware. Firmware is usually shipped
with the driver, and only when updating the firmware a rebuild
should be made.
If unsure say Y here.

FW_LOADER

Userspace firmware loading support

This option is provided for the case where no in-kernel-tree modules
require userspace firmware loading support, but a module built outside
the kernel tree does.

FIRMWARE_IN_KERNEL

Include in-kernel firmware blobs in kernel binary

The kernel source tree includes a number of firmware 'blobs'
which are used by various drivers. The recommended way to
use these is to run "make firmware_install" and to copy the
resulting binary files created in usr/lib/firmware directory
of the kernel tree to the /lib/firmware on your system so
that they can be loaded by userspace helpers on request.

Enabling this option will build each required firmware blob
into the kernel directly, where request_firmware() will find
them without having to call out to userspace. This may be
useful if your root file system requires a device which uses
such firmware, and do not wish to use an initrd.

This single option controls the inclusion of firmware for
every driver which uses request_firmware() and ships its
firmware in the kernel source tree, to avoid a proliferation
of 'Include firmware for xxx device' options.

Say 'N' and let firmware be loaded from userspace.

EXTRA_FIRMWARE

External firmware blobs to build into the kernel binary

This option allows firmware to be built into the kernel, for the
cases where the user either cannot or doesn't want to provide it from
userspace at runtime (for example, when the firmware in question is
required for accessing the boot device, and the user doesn't want to
use an initrd).

This option is a string, and takes the (space-separated) names of the
firmware files -- the same names which appear in MODULE_FIRMWARE()
and request_firmware() in the source. These files should exist under
the directory specified by the EXTRA_FIRMWARE_DIR option, which is
by default the firmware/ subdirectory of the kernel source tree.

So, for example, you might set CONFIG_EXTRA_FIRMWARE="usb8388.bin",
copy the usb8388.bin file into the firmware/ directory, and build the
kernel. Then any request_firmware("usb8388.bin") will be
satisfied internally without needing to call out to userspace.

WARNING: If you include additional firmware files into your binary
kernel image which are not available under the terms of the GPL,
then it may be a violation of the GPL to distribute the resulting
image -- since it combines both GPL and non-GPL work. You should
consult a lawyer of your own before distributing such an image.

EXTRA_FIRMWARE_DIR

Firmware blobs root directory

This option controls the directory in which the kernel build system
looks for the firmware files listed in the EXTRA_FIRMWARE option.
The default is the firmware/ directory in the kernel source tree,
but by changing this option you can point it elsewhere, such as
the /lib/firmware/ directory or another separate directory
containing firmware files.

DEBUG_DRIVER

Driver Core verbose debug messages

Say Y here if you want the Driver core to produce a bunch of
debug messages to the system log. Select this if you are having a
problem with the driver core and want to see more of what is
going on.

If you are unsure about this, say N here.

DEBUG_DEVRES

Managed device resources verbose debug messages

This option enables kernel parameter devres.log. If set to
non-zero, devres debug messages are printed. Select this if
you are having a problem with devres or want to debug
resource management for a managed device. devres.log can be
switched on and off from sysfs node.

If you are unsure about this, Say N here.