Root/drivers/base/Kconfig

1menu "Generic Driver Options"
2
3config UEVENT_HELPER_PATH
4    string "path to uevent helper"
5    depends on HOTPLUG
6    default ""
7    help
8      Path to uevent helper program 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      To disable user space helper program execution at early boot
20      time specify an empty string here. This setting can be altered
21      via /proc/sys/kernel/hotplug or via /sys/kernel/uevent_helper
22      later at runtime.
23
24config DEVTMPFS
25    bool "Maintain a devtmpfs filesystem to mount at /dev"
26    depends on HOTPLUG
27    help
28      This creates a tmpfs/ramfs filesystem instance early at bootup.
29      In this filesystem, the kernel driver core maintains device
30      nodes with their default names and permissions for all
31      registered devices with an assigned major/minor number.
32      Userspace can modify the filesystem content as needed, add
33      symlinks, and apply needed permissions.
34      It provides a fully functional /dev directory, where usually
35      udev runs on top, managing permissions and adding meaningful
36      symlinks.
37      In very limited environments, it may provide a sufficient
38      functional /dev without any further help. It also allows simple
39      rescue systems, and reliably handles dynamic major/minor numbers.
40
41      Notice: if CONFIG_TMPFS isn't enabled, the simpler ramfs
42      file system will be used instead.
43
44config DEVTMPFS_MOUNT
45    bool "Automount devtmpfs at /dev, after the kernel mounted the rootfs"
46    depends on DEVTMPFS
47    help
48      This will instruct the kernel to automatically mount the
49      devtmpfs filesystem at /dev, directly after the kernel has
50      mounted the root filesystem. The behavior can be overridden
51      with the commandline parameter: devtmpfs.mount=0|1.
52      This option does not affect initramfs based booting, here
53      the devtmpfs filesystem always needs to be mounted manually
54      after the roots is mounted.
55      With this option enabled, it allows to bring up a system in
56      rescue mode with init=/bin/sh, even when the /dev directory
57      on the rootfs is completely empty.
58
59config STANDALONE
60    bool "Select only drivers that don't need compile-time external firmware"
61    default y
62    help
63      Select this option if you don't have magic firmware for drivers that
64      need it.
65
66      If unsure, say Y.
67
68config PREVENT_FIRMWARE_BUILD
69    bool "Prevent firmware from being built"
70    default y
71    help
72      Say yes to avoid building firmware. Firmware is usually shipped
73      with the driver and only when updating the firmware should a
74      rebuild be made.
75      If unsure, say Y here.
76
77config FW_LOADER
78    tristate "Userspace firmware loading support" if EXPERT
79    default y
80    ---help---
81      This option is provided for the case where none of the in-tree modules
82      require userspace firmware loading support, but a module built
83      out-of-tree does.
84
85config FIRMWARE_IN_KERNEL
86    bool "Include in-kernel firmware blobs in kernel binary"
87    depends on FW_LOADER
88    default y
89    help
90      The kernel source tree includes a number of firmware 'blobs'
91      that are used by various drivers. The recommended way to
92      use these is to run "make firmware_install", which, after
93      converting ihex files to binary, copies all of the needed
94      binary files in firmware/ to /lib/firmware/ on your system so
95      that they can be loaded by userspace helpers on request.
96
97      Enabling this option will build each required firmware blob
98      into the kernel directly, where request_firmware() will find
99      them without having to call out to userspace. This may be
100      useful if your root file system requires a device that uses
101      such firmware and do not wish to use an initrd.
102
103      This single option controls the inclusion of firmware for
104      every driver that uses request_firmware() and ships its
105      firmware in the kernel source tree, which avoids a
106      proliferation of 'Include firmware for xxx device' options.
107
108      Say 'N' and let firmware be loaded from userspace.
109
110config EXTRA_FIRMWARE
111    string "External firmware blobs to build into the kernel binary"
112    depends on FW_LOADER
113    help
114      This option allows firmware to be built into the kernel for the case
115      where the user either cannot or doesn't want to provide it from
116      userspace at runtime (for example, when the firmware in question is
117      required for accessing the boot device, and the user doesn't want to
118      use an initrd).
119
120      This option is a string and takes the (space-separated) names of the
121      firmware files -- the same names that appear in MODULE_FIRMWARE()
122      and request_firmware() in the source. These files should exist under
123      the directory specified by the EXTRA_FIRMWARE_DIR option, which is
124      by default the firmware subdirectory of the kernel source tree.
125
126      For example, you might set CONFIG_EXTRA_FIRMWARE="usb8388.bin", copy
127      the usb8388.bin file into the firmware directory, and build the kernel.
128      Then any request_firmware("usb8388.bin") will be satisfied internally
129      without needing to call out to userspace.
130
131      WARNING: If you include additional firmware files into your binary
132      kernel image that are not available under the terms of the GPL,
133      then it may be a violation of the GPL to distribute the resulting
134      image since it combines both GPL and non-GPL work. You should
135      consult a lawyer of your own before distributing such an image.
136
137config EXTRA_FIRMWARE_DIR
138    string "Firmware blobs root directory"
139    depends on EXTRA_FIRMWARE != ""
140    default "firmware"
141    help
142      This option controls the directory in which the kernel build system
143      looks for the firmware files listed in the EXTRA_FIRMWARE option.
144      The default is firmware/ in the kernel source tree, but by changing
145      this option you can point it elsewhere, such as /lib/firmware/ or
146      some other directory containing the firmware files.
147
148config FW_LOADER_USER_HELPER
149    bool "Fallback user-helper invocation for firmware loading"
150    depends on FW_LOADER
151    default y
152    help
153      This option enables / disables the invocation of user-helper
154      (e.g. udev) for loading firmware files as a fallback after the
155      direct file loading in kernel fails. The user-mode helper is
156      no longer required unless you have a special firmware file that
157      resides in a non-standard path.
158
159config DEBUG_DRIVER
160    bool "Driver Core verbose debug messages"
161    depends on DEBUG_KERNEL
162    help
163      Say Y here if you want the Driver core to produce a bunch of
164      debug messages to the system log. Select this if you are having a
165      problem with the driver core and want to see more of what is
166      going on.
167
168      If you are unsure about this, say N here.
169
170config DEBUG_DEVRES
171    bool "Managed device resources verbose debug messages"
172    depends on DEBUG_KERNEL
173    help
174      This option enables kernel parameter devres.log. If set to
175      non-zero, devres debug messages are printed. Select this if
176      you are having a problem with devres or want to debug
177      resource management for a managed device. devres.log can be
178      switched on and off from sysfs node.
179
180      If you are unsure about this, Say N here.
181
182config SYS_HYPERVISOR
183    bool
184    default n
185
186config GENERIC_CPU_DEVICES
187    bool
188    default n
189
190config SOC_BUS
191    bool
192
193source "drivers/base/regmap/Kconfig"
194
195config DMA_SHARED_BUFFER
196    bool
197    default n
198    select ANON_INODES
199    help
200      This option enables the framework for buffer-sharing between
201      multiple drivers. A buffer is associated with a file using driver
202      APIs extension; the file's descriptor can then be passed on to other
203      driver.
204
205config CMA
206    bool "Contiguous Memory Allocator"
207    depends on HAVE_DMA_CONTIGUOUS && HAVE_MEMBLOCK
208    select MIGRATION
209    select MEMORY_ISOLATION
210    help
211      This enables the Contiguous Memory Allocator which allows drivers
212      to allocate big physically-contiguous blocks of memory for use with
213      hardware components that do not support I/O map nor scatter-gather.
214
215      For more information see <include/linux/dma-contiguous.h>.
216      If unsure, say "n".
217
218if CMA
219
220config CMA_DEBUG
221    bool "CMA debug messages (DEVELOPMENT)"
222    depends on DEBUG_KERNEL
223    help
224      Turns on debug messages in CMA. This produces KERN_DEBUG
225      messages for every CMA call as well as various messages while
226      processing calls such as dma_alloc_from_contiguous().
227      This option does not affect warning and error messages.
228
229comment "Default contiguous memory area size:"
230
231config CMA_SIZE_MBYTES
232    int "Size in Mega Bytes"
233    depends on !CMA_SIZE_SEL_PERCENTAGE
234    default 16
235    help
236      Defines the size (in MiB) of the default memory area for Contiguous
237      Memory Allocator.
238
239config CMA_SIZE_PERCENTAGE
240    int "Percentage of total memory"
241    depends on !CMA_SIZE_SEL_MBYTES
242    default 10
243    help
244      Defines the size of the default memory area for Contiguous Memory
245      Allocator as a percentage of the total memory in the system.
246
247choice
248    prompt "Selected region size"
249    default CMA_SIZE_SEL_MBYTES
250
251config CMA_SIZE_SEL_MBYTES
252    bool "Use mega bytes value only"
253
254config CMA_SIZE_SEL_PERCENTAGE
255    bool "Use percentage value only"
256
257config CMA_SIZE_SEL_MIN
258    bool "Use lower value (minimum)"
259
260config CMA_SIZE_SEL_MAX
261    bool "Use higher value (maximum)"
262
263endchoice
264
265config CMA_ALIGNMENT
266    int "Maximum PAGE_SIZE order of alignment for contiguous buffers"
267    range 4 9
268    default 8
269    help
270      DMA mapping framework by default aligns all buffers to the smallest
271      PAGE_SIZE order which is greater than or equal to the requested buffer
272      size. This works well for buffers up to a few hundreds kilobytes, but
273      for larger buffers it just a memory waste. With this parameter you can
274      specify the maximum PAGE_SIZE order for contiguous buffers. Larger
275      buffers will be aligned only to this specified order. The order is
276      expressed as a power of two multiplied by the PAGE_SIZE.
277
278      For example, if your system defaults to 4KiB pages, the order value
279      of 8 means that the buffers will be aligned up to 1MiB only.
280
281      If unsure, leave the default value "8".
282
283config CMA_AREAS
284    int "Maximum count of the CMA device-private areas"
285    default 7
286    help
287      CMA allows to create CMA areas for particular devices. This parameter
288      sets the maximum number of such device private CMA areas in the
289      system.
290
291      If unsure, leave the default value "7".
292
293endif
294
295endmenu
296

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