xref: /openbmc/linux/drivers/base/Kconfig (revision 68198dca)
1# SPDX-License-Identifier: GPL-2.0
2menu "Generic Driver Options"
3
4config 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
19config 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
29config 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
48config 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
63config 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
72config 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
81config 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
89config 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
115config 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
142config 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
150config FW_LOADER_USER_HELPER
151	bool
152
153config 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
167config WANT_DEV_COREDUMP
168	bool
169	help
170	  Drivers should "select" this option if they desire to use the
171	  device coredump mechanism.
172
173config 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
186config DEV_COREDUMP
187	bool
188	default y if WANT_DEV_COREDUMP
189	depends on ALLOW_DEV_COREDUMP
190
191config 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
202config 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
214config 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
226source "drivers/base/test/Kconfig"
227
228config SYS_HYPERVISOR
229	bool
230	default n
231
232config GENERIC_CPU_DEVICES
233	bool
234	default n
235
236config GENERIC_CPU_AUTOPROBE
237	bool
238
239config SOC_BUS
240	bool
241	select GLOB
242
243source "drivers/base/regmap/Kconfig"
244
245config DMA_SHARED_BUFFER
246	bool
247	default n
248	select ANON_INODES
249	help
250	  This option enables the framework for buffer-sharing between
251	  multiple drivers. A buffer is associated with a file using driver
252	  APIs extension; the file's descriptor can then be passed on to other
253	  driver.
254
255config DMA_FENCE_TRACE
256	bool "Enable verbose DMA_FENCE_TRACE messages"
257	depends on DMA_SHARED_BUFFER
258	help
259	  Enable the DMA_FENCE_TRACE printks. This will add extra
260	  spam to the console log, but will make it easier to diagnose
261	  lockup related problems for dma-buffers shared across multiple
262	  devices.
263
264config DMA_CMA
265	bool "DMA Contiguous Memory Allocator"
266	depends on HAVE_DMA_CONTIGUOUS && CMA
267	help
268	  This enables the Contiguous Memory Allocator which allows drivers
269	  to allocate big physically-contiguous blocks of memory for use with
270	  hardware components that do not support I/O map nor scatter-gather.
271
272	  You can disable CMA by specifying "cma=0" on the kernel's command
273	  line.
274
275	  For more information see <include/linux/dma-contiguous.h>.
276	  If unsure, say "n".
277
278if  DMA_CMA
279comment "Default contiguous memory area size:"
280
281config CMA_SIZE_MBYTES
282	int "Size in Mega Bytes"
283	depends on !CMA_SIZE_SEL_PERCENTAGE
284	default 0 if X86
285	default 16
286	help
287	  Defines the size (in MiB) of the default memory area for Contiguous
288	  Memory Allocator.  If the size of 0 is selected, CMA is disabled by
289	  default, but it can be enabled by passing cma=size[MG] to the kernel.
290
291
292config CMA_SIZE_PERCENTAGE
293	int "Percentage of total memory"
294	depends on !CMA_SIZE_SEL_MBYTES
295	default 0 if X86
296	default 10
297	help
298	  Defines the size of the default memory area for Contiguous Memory
299	  Allocator as a percentage of the total memory in the system.
300	  If 0 percent is selected, CMA is disabled by default, but it can be
301	  enabled by passing cma=size[MG] to the kernel.
302
303choice
304	prompt "Selected region size"
305	default CMA_SIZE_SEL_MBYTES
306
307config CMA_SIZE_SEL_MBYTES
308	bool "Use mega bytes value only"
309
310config CMA_SIZE_SEL_PERCENTAGE
311	bool "Use percentage value only"
312
313config CMA_SIZE_SEL_MIN
314	bool "Use lower value (minimum)"
315
316config CMA_SIZE_SEL_MAX
317	bool "Use higher value (maximum)"
318
319endchoice
320
321config CMA_ALIGNMENT
322	int "Maximum PAGE_SIZE order of alignment for contiguous buffers"
323	range 4 12
324	default 8
325	help
326	  DMA mapping framework by default aligns all buffers to the smallest
327	  PAGE_SIZE order which is greater than or equal to the requested buffer
328	  size. This works well for buffers up to a few hundreds kilobytes, but
329	  for larger buffers it just a memory waste. With this parameter you can
330	  specify the maximum PAGE_SIZE order for contiguous buffers. Larger
331	  buffers will be aligned only to this specified order. The order is
332	  expressed as a power of two multiplied by the PAGE_SIZE.
333
334	  For example, if your system defaults to 4KiB pages, the order value
335	  of 8 means that the buffers will be aligned up to 1MiB only.
336
337	  If unsure, leave the default value "8".
338
339endif
340
341config GENERIC_ARCH_TOPOLOGY
342	bool
343	help
344	  Enable support for architectures common topology code: e.g., parsing
345	  CPU capacity information from DT, usage of such information for
346	  appropriate scaling, sysfs interface for changing capacity values at
347	  runtime.
348
349endmenu
350