1# SPDX-License-Identifier: GPL-2.0
2menu "Firmware loader"
3
4config FW_LOADER
5	tristate "Firmware loading facility" if EXPERT
6	default y
7	help
8	  This enables the firmware loading facility in the kernel. The kernel
9	  will first look for built-in firmware, if it has any. Next, it will
10	  look for the requested firmware in a series of filesystem paths:
11
12		o firmware_class path module parameter or kernel boot param
13		o /lib/firmware/updates/UTS_RELEASE
14		o /lib/firmware/updates
15		o /lib/firmware/UTS_RELEASE
16		o /lib/firmware
17
18	  Enabling this feature only increases your kernel image by about
19	  828 bytes, enable this option unless you are certain you don't
20	  need firmware.
21
22	  You typically want this built-in (=y) but you can also enable this
23	  as a module, in which case the firmware_class module will be built.
24	  You also want to be sure to enable this built-in if you are going to
25	  enable built-in firmware (CONFIG_EXTRA_FIRMWARE).
26
27if FW_LOADER
28
29config FW_LOADER_PAGED_BUF
30	bool
31
32config EXTRA_FIRMWARE
33	string "Build named firmware blobs into the kernel binary"
34	help
35	  Device drivers which require firmware can typically deal with
36	  having the kernel load firmware from the various supported
37	  /lib/firmware/ paths. This option enables you to build into the
38	  kernel firmware files. Built-in firmware searches are preceded
39	  over firmware lookups using your filesystem over the supported
40	  /lib/firmware paths documented on CONFIG_FW_LOADER.
41
42	  This may be useful for testing or if the firmware is required early on
43	  in boot and cannot rely on the firmware being placed in an initrd or
44	  initramfs.
45
46	  This option is a string and takes the (space-separated) names of the
47	  firmware files -- the same names that appear in MODULE_FIRMWARE()
48	  and request_firmware() in the source. These files should exist under
49	  the directory specified by the EXTRA_FIRMWARE_DIR option, which is
50	  /lib/firmware by default.
51
52	  For example, you might set CONFIG_EXTRA_FIRMWARE="usb8388.bin", copy
53	  the usb8388.bin file into /lib/firmware, and build the kernel. Then
54	  any request_firmware("usb8388.bin") will be satisfied internally
55	  inside the kernel without ever looking at your filesystem at runtime.
56
57	  WARNING: If you include additional firmware files into your binary
58	  kernel image that are not available under the terms of the GPL,
59	  then it may be a violation of the GPL to distribute the resulting
60	  image since it combines both GPL and non-GPL work. You should
61	  consult a lawyer of your own before distributing such an image.
62
63config EXTRA_FIRMWARE_DIR
64	string "Firmware blobs root directory"
65	depends on EXTRA_FIRMWARE != ""
66	default "/lib/firmware"
67	help
68	  This option controls the directory in which the kernel build system
69	  looks for the firmware files listed in the EXTRA_FIRMWARE option.
70
71config FW_LOADER_USER_HELPER
72	bool "Enable the firmware sysfs fallback mechanism"
73	select FW_LOADER_PAGED_BUF
74	help
75	  This option enables a sysfs loading facility to enable firmware
76	  loading to the kernel through userspace as a fallback mechanism
77	  if and only if the kernel's direct filesystem lookup for the
78	  firmware failed using the different /lib/firmware/ paths, or the
79	  path specified in the firmware_class path module parameter, or the
80	  firmware_class path kernel boot parameter if the firmware_class is
81	  built-in. For details on how to work with the sysfs fallback mechanism
82	  refer to Documentation/driver-api/firmware/fallback-mechanisms.rst.
83
84	  The direct filesystem lookup for firmware is always used first now.
85
86	  If the kernel's direct filesystem lookup for firmware fails to find
87	  the requested firmware a sysfs fallback loading facility is made
88	  available and userspace is informed about this through uevents.
89	  The uevent can be suppressed if the driver explicitly requested it,
90	  this is known as the driver using the custom fallback mechanism.
91	  If the custom fallback mechanism is used userspace must always
92	  acknowledge failure to find firmware as the timeout for the fallback
93	  mechanism is disabled, and failed requests will linger forever.
94
95	  This used to be the default firmware loading facility, and udev used
96	  to listen for uvents to load firmware for the kernel. The firmware
97	  loading facility functionality in udev has been removed, as such it
98	  can no longer be relied upon as a fallback mechanism. Linux no longer
99	  relies on or uses a fallback mechanism in userspace. If you need to
100	  rely on one refer to the permissively licensed firmwared:
101
102	  https://github.com/teg/firmwared
103
104	  Since this was the default firmware loading facility at one point,
105	  old userspace may exist which relies upon it, and as such this
106	  mechanism can never be removed from the kernel.
107
108	  You should only enable this functionality if you are certain you
109	  require a fallback mechanism and have a userspace mechanism ready to
110	  load firmware in case it is not found. One main reason for this may
111	  be if you have drivers which require firmware built-in and for
112	  whatever reason cannot place the required firmware in initramfs.
113	  Another reason kernels may have this feature enabled is to support a
114	  driver which explicitly relies on this fallback mechanism. Only two
115	  drivers need this today:
116
117	    o CONFIG_LEDS_LP55XX_COMMON
118	    o CONFIG_DELL_RBU
119
120	  Outside of supporting the above drivers, another reason for needing
121	  this may be that your firmware resides outside of the paths the kernel
122	  looks for and cannot possibly be specified using the firmware_class
123	  path module parameter or kernel firmware_class path boot parameter
124	  if firmware_class is built-in.
125
126	  A modern use case may be to temporarily mount a custom partition
127	  during provisioning which is only accessible to userspace, and then
128	  to use it to look for and fetch the required firmware. Such type of
129	  driver functionality may not even ever be desirable upstream by
130	  vendors, and as such is only required to be supported as an interface
131	  for provisioning. Since udev's firmware loading facility has been
132	  removed you can use firmwared or a fork of it to customize how you
133	  want to load firmware based on uevents issued.
134
135	  Enabling this option will increase your kernel image size by about
136	  13436 bytes.
137
138	  If you are unsure about this, say N here, unless you are Linux
139	  distribution and need to support the above two drivers, or you are
140	  certain you need to support some really custom firmware loading
141	  facility in userspace.
142
143config FW_LOADER_USER_HELPER_FALLBACK
144	bool "Force the firmware sysfs fallback mechanism when possible"
145	depends on FW_LOADER_USER_HELPER
146	help
147	  Enabling this option forces a sysfs userspace fallback mechanism
148	  to be used for all firmware requests which explicitly do not disable a
149	  a fallback mechanism. Firmware calls which do prohibit a fallback
150	  mechanism is request_firmware_direct(). This option is kept for
151	  backward compatibility purposes given this precise mechanism can also
152	  be enabled by setting the proc sysctl value to true:
153
154	       /proc/sys/kernel/firmware_config/force_sysfs_fallback
155
156	  If you are unsure about this, say N here.
157
158config FW_LOADER_COMPRESS
159	bool "Enable compressed firmware support"
160	select FW_LOADER_PAGED_BUF
161	select XZ_DEC
162	help
163	  This option enables the support for loading compressed firmware
164	  files. The caller of firmware API receives the decompressed file
165	  content. The compressed file is loaded as a fallback, only after
166	  loading the raw file failed at first.
167
168	  Currently only XZ-compressed files are supported, and they have to
169	  be compressed with either none or crc32 integrity check type (pass
170	  "-C crc32" option to xz command).
171
172config FW_CACHE
173	bool "Enable firmware caching during suspend"
174	depends on PM_SLEEP
175	default y if PM_SLEEP
176	help
177	  Because firmware caching generates uevent messages that are sent
178	  over a netlink socket, it can prevent suspend on many platforms.
179	  It is also not always useful, so on such platforms we have the
180	  option.
181
182	  If unsure, say Y.
183
184endif # FW_LOADER
185endmenu
186