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Devtmpfs lets the kernel create a tmpfs instance called devtmpfs very early at kernel initialization, before any driver-core device is registered. Every device with a major/minor will provide a device node in devtmpfs. Devtmpfs can be changed and altered by userspace at any time, and in any way needed - just like today's udev-mounted tmpfs. Unmodified udev versions will run just fine on top of it, and will recognize an already existing kernel-created device node and use it. The default node permissions are root:root 0600. Proper permissions and user/group ownership, meaningful symlinks, all other policy still needs to be applied by userspace. If a node is created by devtmps, devtmpfs will remove the device node when the device goes away. If the device node was created by userspace, or the devtmpfs created node was replaced by userspace, it will no longer be removed by devtmpfs. If it is requested to auto-mount it, it makes init=/bin/sh work without any further userspace support. /dev will be fully populated and dynamic, and always reflect the current device state of the kernel. With the commonly used dynamic device numbers, it solves the problem where static devices nodes may point to the wrong devices. It is intended to make the initial bootup logic simpler and more robust, by de-coupling the creation of the inital environment, to reliably run userspace processes, from a complex userspace bootstrap logic to provide a working /dev. Signed-off-by: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: Jan Blunck <jblunck@suse.de> Tested-By: Harald Hoyer <harald@redhat.com> Tested-By: Scott James Remnant <scott@ubuntu.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
155 lines
5.7 KiB
Plaintext
155 lines
5.7 KiB
Plaintext
menu "Generic Driver Options"
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config UEVENT_HELPER_PATH
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string "path to uevent helper"
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depends on HOTPLUG
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default "/sbin/hotplug"
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help
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Path to uevent helper program forked by the kernel for
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every uevent.
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config DEVTMPFS
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bool "Create a kernel maintained /dev tmpfs (EXPERIMENTAL)"
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depends on HOTPLUG && SHMEM && TMPFS
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help
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This creates a tmpfs filesystem, and mounts it at bootup
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and mounts it at /dev. The kernel driver core creates device
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nodes for all registered devices in that filesystem. All device
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nodes are owned by root and have the default mode of 0600.
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Userspace can add and delete the nodes as needed. This is
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intended to simplify bootup, and make it possible to delay
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the initial coldplug at bootup done by udev in userspace.
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It should also provide a simpler way for rescue systems
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to bring up a kernel with dynamic major/minor numbers.
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Meaningful symlinks, permissions and device ownership must
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still be handled by userspace.
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If unsure, say N here.
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config DEVTMPFS_MOUNT
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bool "Automount devtmpfs at /dev"
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depends on DEVTMPFS
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help
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This will mount devtmpfs at /dev if the kernel mounts the root
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filesystem. It will not affect initramfs based mounting.
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If unsure, say N here.
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config STANDALONE
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bool "Select only drivers that don't need compile-time external firmware" if EXPERIMENTAL
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default y
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help
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Select this option if you don't have magic firmware for drivers that
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need it.
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If unsure, say Y.
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config PREVENT_FIRMWARE_BUILD
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bool "Prevent firmware from being built"
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default y
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help
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Say yes to avoid building firmware. Firmware is usually shipped
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with the driver, and only when updating the firmware a rebuild
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should be made.
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If unsure say Y here.
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config FW_LOADER
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tristate "Userspace firmware loading support" if EMBEDDED
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depends on HOTPLUG
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default y
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---help---
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This option is provided for the case where no in-kernel-tree modules
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require userspace firmware loading support, but a module built outside
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the kernel tree does.
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config FIRMWARE_IN_KERNEL
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bool "Include in-kernel firmware blobs in kernel binary"
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depends on FW_LOADER
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default y
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help
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The kernel source tree includes a number of firmware 'blobs'
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which are used by various drivers. The recommended way to
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use these is to run "make firmware_install" and to copy the
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resulting binary files created in usr/lib/firmware directory
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of the kernel tree to the /lib/firmware on your system so
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that they can be loaded by userspace helpers on request.
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Enabling this option will build each required firmware blob
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into the kernel directly, where request_firmware() will find
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them without having to call out to userspace. This may be
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useful if your root file system requires a device which uses
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such firmware, and do not wish to use an initrd.
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This single option controls the inclusion of firmware for
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every driver which uses request_firmware() and ships its
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firmware in the kernel source tree, to avoid a proliferation
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of 'Include firmware for xxx device' options.
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Say 'N' and let firmware be loaded from userspace.
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config EXTRA_FIRMWARE
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string "External firmware blobs to build into the kernel binary"
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depends on FW_LOADER
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help
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This option allows firmware to be built into the kernel, for the
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cases where the user either cannot or doesn't want to provide it from
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userspace at runtime (for example, when the firmware in question is
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required for accessing the boot device, and the user doesn't want to
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use an initrd).
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This option is a string, and takes the (space-separated) names of the
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firmware files -- the same names which appear in MODULE_FIRMWARE()
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and request_firmware() in the source. These files should exist under
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the directory specified by the EXTRA_FIRMWARE_DIR option, which is
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by default the firmware/ subdirectory of the kernel source tree.
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So, for example, you might set CONFIG_EXTRA_FIRMWARE="usb8388.bin",
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copy the usb8388.bin file into the firmware/ directory, and build the
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kernel. Then any request_firmware("usb8388.bin") will be
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satisfied internally without needing to call out to userspace.
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WARNING: If you include additional firmware files into your binary
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kernel image which are not available under the terms of the GPL,
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then it may be a violation of the GPL to distribute the resulting
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image -- since it combines both GPL and non-GPL work. You should
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consult a lawyer of your own before distributing such an image.
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config EXTRA_FIRMWARE_DIR
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string "Firmware blobs root directory"
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depends on EXTRA_FIRMWARE != ""
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default "firmware"
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help
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This option controls the directory in which the kernel build system
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looks for the firmware files listed in the EXTRA_FIRMWARE option.
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The default is the firmware/ directory in the kernel source tree,
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but by changing this option you can point it elsewhere, such as
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the /lib/firmware/ directory or another separate directory
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containing firmware files.
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config DEBUG_DRIVER
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bool "Driver Core verbose debug messages"
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depends on DEBUG_KERNEL
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help
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Say Y here if you want the Driver core to produce a bunch of
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debug messages to the system log. Select this if you are having a
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problem with the driver core and want to see more of what is
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going on.
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If you are unsure about this, say N here.
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config DEBUG_DEVRES
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bool "Managed device resources verbose debug messages"
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depends on DEBUG_KERNEL
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help
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This option enables kernel parameter devres.log. If set to
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non-zero, devres debug messages are printed. Select this if
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you are having a problem with devres or want to debug
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resource management for a managed device. devres.log can be
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switched on and off from sysfs node.
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If you are unsure about this, Say N here.
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config SYS_HYPERVISOR
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bool
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default n
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endmenu
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