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           Various drivers in the kernel source tree may require firmware,
  95           which is generally available in your distribution's linux-firmware
  96           package.
  97
  98           The linux-firmware package should install firmware into
  99           /lib/firmware/ on your system, so they can be loaded by userspace
 100           helpers on request.
 101
 102           Enabling this option will build each required firmware blob
 103           specified by EXTRA_FIRMWARE into the kernel directly, where
 104           request_firmware() will find them without having to call out to
 105           userspace. This may be useful if your root file system requires a
 106           device that uses such firmware and you do not wish to use an
 107           initrd.
 108
 109           This single option controls the inclusion of firmware for
 110           every driver that uses request_firmware(), which avoids a
 111           proliferation of 'Include firmware for xxx device' options.
 112
 113           Say 'N' and let firmware be loaded from userspace.
 114
 115 config EXTRA_FIRMWARE
 116         string "External firmware blobs to build into the kernel binary"
 117         depends on FW_LOADER
 118         help
 119           This option allows firmware to be built into the kernel for the case
 120           where the user either cannot or doesn't want to provide it from
 121           userspace at runtime (for example, when the firmware in question is
 122           required for accessing the boot device, and the user doesn't want to
 123           use an initrd).
 124
 125           This option is a string and takes the (space-separated) names of the
 126           firmware files -- the same names that appear in MODULE_FIRMWARE()
 127           and request_firmware() in the source. These files should exist under
 128           the directory specified by the EXTRA_FIRMWARE_DIR option, which is
 129           by default the firmware subdirectory of the kernel source tree.
 130
 131           For example, you might set CONFIG_EXTRA_FIRMWARE="usb8388.bin", copy
 132           the usb8388.bin file into the firmware directory, and build the kernel.
 133           Then any request_firmware("usb8388.bin") will be satisfied internally
 134           without needing to call out to userspace.
 135
 136           WARNING: If you include additional firmware files into your binary
 137           kernel image that are not available under the terms of the GPL,
 138           then it may be a violation of the GPL to distribute the resulting
 139           image since it combines both GPL and non-GPL work. You should
 140           consult a lawyer of your own before distributing such an image.
 141
 142 config EXTRA_FIRMWARE_DIR
 143         string "Firmware blobs root directory"
 144         depends on EXTRA_FIRMWARE != ""
 145         default "/lib/firmware"
 146         help
 147           This option controls the directory in which the kernel build system
 148           looks for the firmware files listed in the EXTRA_FIRMWARE option.
 149
 150 config FW_LOADER_USER_HELPER
 151         bool
 152
 153 config FW_LOADER_USER_HELPER_FALLBACK
 154         bool "Fallback user-helper invocation for firmware loading"
 155         depends on FW_LOADER
 156         select FW_LOADER_USER_HELPER
 157         help
 158           This option enables / disables the invocation of user-helper
 159           (e.g. udev) for loading firmware files as a fallback after the
 160           direct file loading in kernel fails.  The user-mode helper is
 161           no longer required unless you have a special firmware file that
 162           resides in a non-standard path. Moreover, the udev support has
 163           been deprecated upstream.
 164
 165           If you are unsure about this, say N here.
 166
 167 config WANT_DEV_COREDUMP
 168         bool
 169         help
 170           Drivers should "select" this option if they desire to use the
 171           device coredump mechanism.
 172
 173 config ALLOW_DEV_COREDUMP
 174         bool "Allow device coredump" if EXPERT
 175         default y
 176         help
 177           This option controls if the device coredump mechanism is available or
 178           not; if disabled, the mechanism will be omitted even if drivers that
 179           can use it are enabled.
 180           Say 'N' for more sensitive systems or systems that don't want
 181           to ever access the information to not have the code, nor keep any
 182           data.
 183
 184           If unsure, say Y.
 185
 186 config DEV_COREDUMP
 187         bool
 188         default y if WANT_DEV_COREDUMP
 189         depends on ALLOW_DEV_COREDUMP
 190
 191 config DEBUG_DRIVER
 192         bool "Driver Core verbose debug messages"
 193         depends on DEBUG_KERNEL
 194         help
 195           Say Y here if you want the Driver core to produce a bunch of
 196           debug messages to the system log. Select this if you are having a
 197           problem with the driver core and want to see more of what is
 198           going on.
 199
 200           If you are unsure about this, say N here.
 201
 202 config DEBUG_DEVRES
 203         bool "Managed device resources verbose debug messages"
 204         depends on DEBUG_KERNEL
 205         help
 206           This option enables kernel parameter devres.log. If set to
 207           non-zero, devres debug messages are printed. Select this if
 208           you are having a problem with devres or want to debug
 209           resource management for a managed device. devres.log can be
 210           switched on and off from sysfs node.
 211
 212           If you are unsure about this, Say N here.
 213
 214 config DEBUG_TEST_DRIVER_REMOVE
 215         bool "Test driver remove calls during probe (UNSTABLE)"
 216         depends on DEBUG_KERNEL
 217         help
 218           Say Y here if you want the Driver core to test driver remove functions
 219           by calling probe, remove, probe. This tests the remove path without
 220           having to unbind the driver or unload the driver module.
 221
 222           This option is expected to find errors and may render your system
 223           unusable. You should say N here unless you are explicitly looking to
 224           test this functionality.
 225
 226 source "drivers/base/test/Kconfig"
 227
 228 config SYS_HYPERVISOR
 229         bool
 230         default n
 231
 232 config GENERIC_CPU_DEVICES
 233         bool
 234         default n
 235
 236 config GENERIC_CPU_AUTOPROBE
 237         bool
 238
 239 config GENERIC_CPU_VULNERABILITIES
 240         bool
 241
 242 config SOC_BUS
 243         bool
 244         select GLOB
 245
 246 source "drivers/base/regmap/Kconfig"
 247
 248 config DMA_SHARED_BUFFER
 249         bool
 250         default n
 251         select ANON_INODES
 252         help
 253           This option enables the framework for buffer-sharing between
 254           multiple drivers. A buffer is associated with a file using driver
 255           APIs extension; the file's descriptor can then be passed on to other
 256           driver.
 257
 258 config DMA_FENCE_TRACE
 259         bool "Enable verbose DMA_FENCE_TRACE messages"
 260         depends on DMA_SHARED_BUFFER
 261         help
 262           Enable the DMA_FENCE_TRACE printks. This will add extra
 263           spam to the console log, but will make it easier to diagnose
 264           lockup related problems for dma-buffers shared across multiple
 265           devices.
 266
 267 config DMA_CMA
 268         bool "DMA Contiguous Memory Allocator"
 269         depends on HAVE_DMA_CONTIGUOUS && CMA
 270         help
 271           This enables the Contiguous Memory Allocator which allows drivers
 272           to allocate big physically-contiguous blocks of memory for use with
 273           hardware components that do not support I/O map nor scatter-gather.
 274
 275           You can disable CMA by specifying "cma=0" on the kernel's command
 276           line.
 277
 278           For more information see <include/linux/dma-contiguous.h>.
 279           If unsure, say "n".
 280
 281 if  DMA_CMA
 282 comment "Default contiguous memory area size:"
 283
 284 config CMA_SIZE_MBYTES
 285         int "Size in Mega Bytes"
 286         depends on !CMA_SIZE_SEL_PERCENTAGE
 287         default 0 if X86
 288         default 16
 289         help
 290           Defines the size (in MiB) of the default memory area for Contiguous
 291           Memory Allocator.  If the size of 0 is selected, CMA is disabled by
 292           default, but it can be enabled by passing cma=size[MG] to the kernel.
 293
 294
 295 config CMA_SIZE_PERCENTAGE
 296         int "Percentage of total memory"
 297         depends on !CMA_SIZE_SEL_MBYTES
 298         default 0 if X86
 299         default 10
 300         help
 301           Defines the size of the default memory area for Contiguous Memory
 302           Allocator as a percentage of the total memory in the system.
 303           If 0 percent is selected, CMA is disabled by default, but it can be
 304           enabled by passing cma=size[MG] to the kernel.
 305
 306 choice
 307         prompt "Selected region size"
 308         default CMA_SIZE_SEL_MBYTES
 309
 310 config CMA_SIZE_SEL_MBYTES
 311         bool "Use mega bytes value only"
 312
 313 config CMA_SIZE_SEL_PERCENTAGE
 314         bool "Use percentage value only"
 315
 316 config CMA_SIZE_SEL_MIN
 317         bool "Use lower value (minimum)"
 318
 319 config CMA_SIZE_SEL_MAX
 320         bool "Use higher value (maximum)"
 321
 322 endchoice
 323
 324 config CMA_ALIGNMENT
 325         int "Maximum PAGE_SIZE order of alignment for contiguous buffers"
 326         range 4 12
 327         default 8
 328         help
 329           DMA mapping framework by default aligns all buffers to the smallest
 330           PAGE_SIZE order which is greater than or equal to the requested buffer
 331           size. This works well for buffers up to a few hundreds kilobytes, but
 332           for larger buffers it just a memory waste. With this parameter you can
 333           specify the maximum PAGE_SIZE order for contiguous buffers. Larger
 334           buffers will be aligned only to this specified order. The order is
 335           expressed as a power of two multiplied by the PAGE_SIZE.
 336
 337           For example, if your system defaults to 4KiB pages, the order value
 338           of 8 means that the buffers will be aligned up to 1MiB only.
 339
 340           If unsure, leave the default value "8".
 341
 342 endif
 343
 344 config GENERIC_ARCH_TOPOLOGY
 345         bool
 346         help
 347           Enable support for architectures common topology code: e.g., parsing
 348           CPU capacity information from DT, usage of such information for
 349           appropriate scaling, sysfs interface for changing capacity values at
 350           runtime.
 351
 352 endmenu