menu "Generic Driver Options"
string "path to uevent helper"
Path to uevent helper program forked by the kernel for
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.
To disable user space helper program execution at early boot
time specify an empty string here. This setting can be altered
via /proc/sys/kernel/hotplug or via /sys/kernel/uevent_helper
later at runtime.
bool "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
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.
bool "Automount devtmpfs at /dev, after the kernel mounted the rootfs"
depends on DEVTMPFS
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 rootfs 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.
bool "Select only drivers that don't need compile-time external firmware"
Select this option if you don't have magic firmware for drivers that
If unsure, say Y.
bool "Prevent firmware from being built"
Say yes to avoid building firmware. Firmware is usually shipped
with the driver and only when updating the firmware should a
rebuild be made.
If unsure, say Y here.
tristate "Userspace firmware loading support" if EXPERT
This option is provided for the case where none of the in-tree modules
require userspace firmware loading support, but a module built
bool "Include in-kernel firmware blobs in kernel binary"
depends on FW_LOADER
The kernel source tree includes a number of firmware 'blobs'
that are used by various drivers. The recommended way to
use these is to run "make firmware_install", which, after
converting ihex files to binary, copies all of the needed
binary files in firmware/ to /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 that uses
such firmware and do not wish to use an initrd.
This single option controls the inclusion of firmware for
every driver that uses request_firmware() and ships its
firmware in the kernel source tree, which avoids a
proliferation of 'Include firmware for xxx device' options.
Say 'N' and let firmware be loaded from userspace.
string "External firmware blobs to build into the kernel binary"
depends on FW_LOADER
This option allows firmware to be built into the kernel for the case
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 that 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.
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 that 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.
string "Firmware blobs root directory"
depends on EXTRA_FIRMWARE != ""
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 firmware/ in the kernel source tree, but by changing
this option you can point it elsewhere, such as /lib/firmware/ or
some other directory containing the firmware files.
bool "Fallback user-helper invocation for firmware loading"
depends on FW_LOADER
This option enables / disables the invocation of user-helper
(e.g. udev) for loading firmware files as a fallback after the
direct file loading in kernel fails. The user-mode helper is
no longer required unless you have a special firmware file that
resides in a non-standard path.
bool "Driver Core verbose debug messages"
depends on DEBUG_KERNEL
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
If you are unsure about this, say N here.
bool "Managed device resources verbose debug messages"
depends on DEBUG_KERNEL
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.
This option enables the framework for buffer-sharing between
multiple drivers. A buffer is associated with a file using driver
APIs extension; the file's descriptor can then be passed on to other
bool "DMA Contiguous Memory Allocator"
depends on HAVE_DMA_CONTIGUOUS && CMA
This enables the Contiguous Memory Allocator which allows drivers
to allocate big physically-contiguous blocks of memory for use with
hardware components that do not support I/O map nor scatter-gather.
For more information see <include/linux/dma-contiguous.h>.
If unsure, say "n".
comment "Default contiguous memory area size:"
int "Size in Mega Bytes"
depends on !CMA_SIZE_SEL_PERCENTAGE
Defines the size (in MiB) of the default memory area for Contiguous
int "Percentage of total memory"
depends on !CMA_SIZE_SEL_MBYTES
Defines the size of the default memory area for Contiguous Memory
Allocator as a percentage of the total memory in the system.
prompt "Selected region size"
bool "Use mega bytes value only"
bool "Use percentage value only"
bool "Use lower value (minimum)"
bool "Use higher value (maximum)"
int "Maximum PAGE_SIZE order of alignment for contiguous buffers"
range 4 9
DMA mapping framework by default aligns all buffers to the smallest
PAGE_SIZE order which is greater than or equal to the requested buffer
size. This works well for buffers up to a few hundreds kilobytes, but
for larger buffers it just a memory waste. With this parameter you can
specify the maximum PAGE_SIZE order for contiguous buffers. Larger
buffers will be aligned only to this specified order. The order is
expressed as a power of two multiplied by the PAGE_SIZE.
For example, if your system defaults to 4KiB pages, the order value
of 8 means that the buffers will be aligned up to 1MiB only.
If unsure, leave the default value "8".
int "Maximum count of the CMA device-private areas"
CMA allows to create CMA areas for particular devices. This parameter
sets the maximum number of such device private CMA areas in the
If unsure, leave the default value "7".