drivers/base/Kconfig

   1 # SPDX-License-Identifier: GPL-2.0
   2 menu "Generic Driver Options"
   3
   4 config UEVENT_HELPER
   5         bool "Support for uevent helper"
   6         default y
   7         help
   8           The uevent helper program is forked by the kernel for
   9           every uevent.
  10           Before the switch to the netlink-based uevent source, this was
  11           used to hook hotplug scripts into kernel device events. It
  12           usually pointed to a shell script at /sbin/hotplug.
  13           This should not be used today, because usual systems create
  14           many events at bootup or device discovery in a very short time
  15           frame. One forked process per event can create so many processes
  16           that it creates a high system load, or on smaller systems
  17           it is known to create out-of-memory situations during bootup.
  18
  19 config UEVENT_HELPER_PATH
  20         string "path to uevent helper"
  21         depends on UEVENT_HELPER
  22         default ""
  23         help
  24           To disable user space helper program execution at by default
  25           specify an empty string here. This setting can still be altered
  26           via /proc/sys/kernel/hotplug or via /sys/kernel/uevent_helper
  27           later at runtime.
  28
  29 config DEVTMPFS
  30         bool "Maintain a devtmpfs filesystem to mount at /dev"
  31         help
  32           This creates a tmpfs/ramfs filesystem instance early at bootup.
  33           In this filesystem, the kernel driver core maintains device
  34           nodes with their default names and permissions for all
  35           registered devices with an assigned major/minor number.
  36           Userspace can modify the filesystem content as needed, add
  37           symlinks, and apply needed permissions.
  38           It provides a fully functional /dev directory, where usually
  39           udev runs on top, managing permissions and adding meaningful
  40           symlinks.
  41           In very limited environments, it may provide a sufficient
  42           functional /dev without any further help. It also allows simple
  43           rescue systems, and reliably handles dynamic major/minor numbers.
  44
  45           Notice: if CONFIG_TMPFS isn't enabled, the simpler ramfs
  46           file system will be used instead.
  47
  48 config DEVTMPFS_MOUNT
  49         bool "Automount devtmpfs at /dev, after the kernel mounted the rootfs"
  50         depends on DEVTMPFS
  51         help
  52           This will instruct the kernel to automatically mount the
  53           devtmpfs filesystem at /dev, directly after the kernel has
  54           mounted the root filesystem. The behavior can be overridden
  55           with the commandline parameter: devtmpfs.mount=0|1.
  56           This option does not affect initramfs based booting, here
  57           the devtmpfs filesystem always needs to be mounted manually
  58           after the rootfs is mounted.
  59           With this option enabled, it allows to bring up a system in
  60           rescue mode with init=/bin/sh, even when the /dev directory
  61           on the rootfs is completely empty.
  62
  63 config STANDALONE
  64         bool "Select only drivers that don't need compile-time external firmware"
  65         default y
  66         help
  67           Select this option if you don't have magic firmware for drivers that
  68           need it.
  69
  70           If unsure, say Y.
  71
  72 config PREVENT_FIRMWARE_BUILD
  73         bool "Prevent firmware from being built"
  74         default y
  75         help
  76           Say yes to avoid building firmware. Firmware is usually shipped
  77           with the driver and only when updating the firmware should a
  78           rebuild be made.
  79           If unsure, say Y here.
  80
  81 config FW_LOADER
  82         tristate "Userspace firmware loading support" if EXPERT
  83         default y
  84         ---help---
  85           This option is provided for the case where none of the in-tree modules
  86           require userspace firmware loading support, but a module built
  87           out-of-tree does.
  88
  89 config FIRMWARE_IN_KERNEL
  90         bool "Include in-kernel firmware blobs in kernel binary"
  91         depends on FW_LOADER
  92         default y
  93         help
  94           The kernel source tree includes a number of firmware 'blobs'
  95           that are used by various drivers. The recommended way to
  96           use these is to run "make firmware_install", which, after
  97           converting ihex files to binary, copies all of the needed
  98           binary files in firmware/ to /lib/firmware/ on your system so
  99           that they can be loaded by userspace helpers on request.
 100
 101           Enabling this option will build each required firmware blob
 102           into the kernel directly, where request_firmware() will find
 103           them without having to call out to userspace. This may be
 104           useful if your root file system requires a device that uses
 105           such firmware and do not wish to use an initrd.
 106
 107           This single option controls the inclusion of firmware for
 108           every driver that uses request_firmware() and ships its
 109           firmware in the kernel source tree, which avoids a
 110           proliferation of 'Include firmware for xxx device' options.
 111
 112           Say 'N' and let firmware be loaded from userspace.
 113
 114 config EXTRA_FIRMWARE
 115         string "External firmware blobs to build into the kernel binary"
 116         depends on FW_LOADER
 117         help
 118           This option allows firmware to be built into the kernel for the case
 119           where the user either cannot or doesn't want to provide it from
 120           userspace at runtime (for example, when the firmware in question is
 121           required for accessing the boot device, and the user doesn't want to
 122           use an initrd).
 123
 124           This option is a string and takes the (space-separated) names of the
 125           firmware files -- the same names that appear in MODULE_FIRMWARE()
 126           and request_firmware() in the source. These files should exist under
 127           the directory specified by the EXTRA_FIRMWARE_DIR option, which is
 128           by default the firmware subdirectory of the kernel source tree.
 129
 130           For example, you might set CONFIG_EXTRA_FIRMWARE="usb8388.bin", copy
 131           the usb8388.bin file into the firmware directory, and build the kernel.
 132           Then any request_firmware("usb8388.bin") will be satisfied internally
 133           without needing to call out to userspace.
 134
 135           WARNING: If you include additional firmware files into your binary
 136           kernel image that are not available under the terms of the GPL,
 137           then it may be a violation of the GPL to distribute the resulting
 138           image since it combines both GPL and non-GPL work. You should
 139           consult a lawyer of your own before distributing such an image.
 140
 141 config EXTRA_FIRMWARE_DIR
 142         string "Firmware blobs root directory"
 143         depends on EXTRA_FIRMWARE != ""
 144         default "/lib/firmware"
 145         help
 146           This option controls the directory in which the kernel build system
 147           looks for the firmware files listed in the EXTRA_FIRMWARE option.
 148
 149 config FW_LOADER_USER_HELPER
 150         bool
 151
 152 config FW_LOADER_USER_HELPER_FALLBACK
 153         bool "Fallback user-helper invocation for firmware loading"
 154         depends on FW_LOADER
 155         select FW_LOADER_USER_HELPER
 156         help
 157           This option enables / disables the invocation of user-helper
 158           (e.g. udev) for loading firmware files as a fallback after the
 159           direct file loading in kernel fails.  The user-mode helper is
 160           no longer required unless you have a special firmware file that
 161           resides in a non-standard path. Moreover, the udev support has
 162           been deprecated upstream.
 163
 164           If you are unsure about this, say N here.
 165
 166 config WANT_DEV_COREDUMP
 167         bool
 168         help
 169           Drivers should "select" this option if they desire to use the
 170           device coredump mechanism.
 171
 172 config ALLOW_DEV_COREDUMP
 173         bool "Allow device coredump" if EXPERT
 174         default y
 175         help
 176           This option controls if the device coredump mechanism is available or
 177           not; if disabled, the mechanism will be omitted even if drivers that
 178           can use it are enabled.
 179           Say 'N' for more sensitive systems or systems that don't want
 180           to ever access the information to not have the code, nor keep any
 181           data.
 182
 183           If unsure, say Y.
 184
 185 config DEV_COREDUMP
 186         bool
 187         default y if WANT_DEV_COREDUMP
 188         depends on ALLOW_DEV_COREDUMP
 189
 190 config DEBUG_DRIVER
 191         bool "Driver Core verbose debug messages"
 192         depends on DEBUG_KERNEL
 193         help
 194           Say Y here if you want the Driver core to produce a bunch of
 195           debug messages to the system log. Select this if you are having a
 196           problem with the driver core and want to see more of what is
 197           going on.
 198
 199           If you are unsure about this, say N here.
 200
 201 config DEBUG_DEVRES
 202         bool "Managed device resources verbose debug messages"
 203         depends on DEBUG_KERNEL
 204         help
 205           This option enables kernel parameter devres.log. If set to
 206           non-zero, devres debug messages are printed. Select this if
 207           you are having a problem with devres or want to debug
 208           resource management for a managed device. devres.log can be
 209           switched on and off from sysfs node.
 210
 211           If you are unsure about this, Say N here.
 212
 213 config DEBUG_TEST_DRIVER_REMOVE
 214         bool "Test driver remove calls during probe (UNSTABLE)"
 215         depends on DEBUG_KERNEL
 216         help
 217           Say Y here if you want the Driver core to test driver remove functions
 218           by calling probe, remove, probe. This tests the remove path without
 219           having to unbind the driver or unload the driver module.
 220
 221           This option is expected to find errors and may render your system
 222           unusable. You should say N here unless you are explicitly looking to
 223           test this functionality.
 224
 225 source "drivers/base/test/Kconfig"
 226
 227 config SYS_HYPERVISOR
 228         bool
 229         default n
 230
 231 config GENERIC_CPU_DEVICES
 232         bool
 233         default n
 234
 235 config GENERIC_CPU_AUTOPROBE
 236         bool
 237
 238 config SOC_BUS
 239         bool
 240         select GLOB
 241
 242 source "drivers/base/regmap/Kconfig"
 243
 244 config DMA_SHARED_BUFFER
 245         bool
 246         default n
 247         select ANON_INODES
 248         help
 249           This option enables the framework for buffer-sharing between
 250           multiple drivers. A buffer is associated with a file using driver
 251           APIs extension; the file's descriptor can then be passed on to other
 252           driver.
 253
 254 config DMA_FENCE_TRACE
 255         bool "Enable verbose DMA_FENCE_TRACE messages"
 256         depends on DMA_SHARED_BUFFER
 257         help
 258           Enable the DMA_FENCE_TRACE printks. This will add extra
 259           spam to the console log, but will make it easier to diagnose
 260           lockup related problems for dma-buffers shared across multiple
 261           devices.
 262
 263 config DMA_CMA
 264         bool "DMA Contiguous Memory Allocator"
 265         depends on HAVE_DMA_CONTIGUOUS && CMA
 266         help
 267           This enables the Contiguous Memory Allocator which allows drivers
 268           to allocate big physically-contiguous blocks of memory for use with
 269           hardware components that do not support I/O map nor scatter-gather.
 270
 271           You can disable CMA by specifying "cma=0" on the kernel's command
 272           line.
 273
 274           For more information see <include/linux/dma-contiguous.h>.
 275           If unsure, say "n".
 276
 277 if  DMA_CMA
 278 comment "Default contiguous memory area size:"
 279
 280 config CMA_SIZE_MBYTES
 281         int "Size in Mega Bytes"
 282         depends on !CMA_SIZE_SEL_PERCENTAGE
 283         default 0 if X86
 284         default 16
 285         help
 286           Defines the size (in MiB) of the default memory area for Contiguous
 287           Memory Allocator.  If the size of 0 is selected, CMA is disabled by
 288           default, but it can be enabled by passing cma=size[MG] to the kernel.
 289
 290
 291 config CMA_SIZE_PERCENTAGE
 292         int "Percentage of total memory"
 293         depends on !CMA_SIZE_SEL_MBYTES
 294         default 0 if X86
 295         default 10
 296         help
 297           Defines the size of the default memory area for Contiguous Memory
 298           Allocator as a percentage of the total memory in the system.
 299           If 0 percent is selected, CMA is disabled by default, but it can be
 300           enabled by passing cma=size[MG] to the kernel.
 301
 302 choice
 303         prompt "Selected region size"
 304         default CMA_SIZE_SEL_MBYTES
 305
 306 config CMA_SIZE_SEL_MBYTES
 307         bool "Use mega bytes value only"
 308
 309 config CMA_SIZE_SEL_PERCENTAGE
 310         bool "Use percentage value only"
 311
 312 config CMA_SIZE_SEL_MIN
 313         bool "Use lower value (minimum)"
 314
 315 config CMA_SIZE_SEL_MAX
 316         bool "Use higher value (maximum)"
 317
 318 endchoice
 319
 320 config CMA_ALIGNMENT
 321         int "Maximum PAGE_SIZE order of alignment for contiguous buffers"
 322         range 4 12
 323         default 8
 324         help
 325           DMA mapping framework by default aligns all buffers to the smallest
 326           PAGE_SIZE order which is greater than or equal to the requested buffer
 327           size. This works well for buffers up to a few hundreds kilobytes, but
 328           for larger buffers it just a memory waste. With this parameter you can
 329           specify the maximum PAGE_SIZE order for contiguous buffers. Larger
 330           buffers will be aligned only to this specified order. The order is
 331           expressed as a power of two multiplied by the PAGE_SIZE.
 332
 333           For example, if your system defaults to 4KiB pages, the order value
 334           of 8 means that the buffers will be aligned up to 1MiB only.
 335
 336           If unsure, leave the default value "8".
 337
 338 endif
 339
 340 config GENERIC_ARCH_TOPOLOGY
 341         bool
 342         help
 343           Enable support for architectures common topology code: e.g., parsing
 344           CPU capacity information from DT, usage of such information for
 345           appropriate scaling, sysfs interface for changing capacity values at
 346           runtime.
 347
 348 endmenu