1menu "Firmware loader"
2
3config FW_LOADER
4	tristate "Firmware loading facility" if EXPERT
5	default y
6	help
7	  This enables the firmware loading facility in the kernel. The kernel
8	  will first look for built-in firmware, if it has any. Next, it will
9	  look for the requested firmware in a series of filesystem paths:
10
11		o firmware_class path module parameter or kernel boot param
12		o /lib/firmware/updates/UTS_RELEASE
13		o /lib/firmware/updates
14		o /lib/firmware/UTS_RELEASE
15		o /lib/firmware
16
17	  Enabling this feature only increases your kernel image by about
18	  828 bytes, enable this option unless you are certain you don't
19	  need firmware.
20
21	  You typically want this built-in (=y) but you can also enable this
22	  as a module, in which case the firmware_class module will be built.
23	  You also want to be sure to enable this built-in if you are going to
24	  enable built-in firmware (CONFIG_EXTRA_FIRMWARE).
25
26if FW_LOADER
27
28config EXTRA_FIRMWARE
29	string "Build named firmware blobs into the kernel binary"
30	help
31	  Device drivers which require firmware can typically deal with
32	  having the kernel load firmware from the various supported
33	  /lib/firmware/ paths. This option enables you to build into the
34	  kernel firmware files. Built-in firmware searches are preceded
35	  over firmware lookups using your filesystem over the supported
36	  /lib/firmware paths documented on CONFIG_FW_LOADER.
37
38	  This may be useful for testing or if the firmware is required early on
39	  in boot and cannot rely on the firmware being placed in an initrd or
40	  initramfs.
41
42	  This option is a string and takes the (space-separated) names of the
43	  firmware files -- the same names that appear in MODULE_FIRMWARE()
44	  and request_firmware() in the source. These files should exist under
45	  the directory specified by the EXTRA_FIRMWARE_DIR option, which is
46	  /lib/firmware by default.
47
48	  For example, you might set CONFIG_EXTRA_FIRMWARE="usb8388.bin", copy
49	  the usb8388.bin file into /lib/firmware, and build the kernel. Then
50	  any request_firmware("usb8388.bin") will be satisfied internally
51	  inside the kernel without ever looking at your filesystem at runtime.
52
53	  WARNING: If you include additional firmware files into your binary
54	  kernel image that are not available under the terms of the GPL,
55	  then it may be a violation of the GPL to distribute the resulting
56	  image since it combines both GPL and non-GPL work. You should
57	  consult a lawyer of your own before distributing such an image.
58
59config EXTRA_FIRMWARE_DIR
60	string "Firmware blobs root directory"
61	depends on EXTRA_FIRMWARE != ""
62	default "/lib/firmware"
63	help
64	  This option controls the directory in which the kernel build system
65	  looks for the firmware files listed in the EXTRA_FIRMWARE option.
66
67config FW_LOADER_USER_HELPER
68	bool "Enable the firmware sysfs fallback mechanism"
69	help
70	  This option enables a sysfs loading facility to enable firmware
71	  loading to the kernel through userspace as a fallback mechanism
72	  if and only if the kernel's direct filesystem lookup for the
73	  firmware failed using the different /lib/firmware/ paths, or the
74	  path specified in the firmware_class path module parameter, or the
75	  firmware_class path kernel boot parameter if the firmware_class is
76	  built-in. For details on how to work with the sysfs fallback mechanism
77	  refer to Documentation/driver-api/firmware/fallback-mechanisms.rst.
78
79	  The direct filesystem lookup for firmware is always used first now.
80
81	  If the kernel's direct filesystem lookup for firmware fails to find
82	  the requested firmware a sysfs fallback loading facility is made
83	  available and userspace is informed about this through uevents.
84	  The uevent can be suppressed if the driver explicitly requested it,
85	  this is known as the driver using the custom fallback mechanism.
86	  If the custom fallback mechanism is used userspace must always
87	  acknowledge failure to find firmware as the timeout for the fallback
88	  mechanism is disabled, and failed requests will linger forever.
89
90	  This used to be the default firmware loading facility, and udev used
91	  to listen for uvents to load firmware for the kernel. The firmware
92	  loading facility functionality in udev has been removed, as such it
93	  can no longer be relied upon as a fallback mechanism. Linux no longer
94	  relies on or uses a fallback mechanism in userspace. If you need to
95	  rely on one refer to the permissively licensed firmwared:
96
97	  https://github.com/teg/firmwared
98
99	  Since this was the default firmware loading facility at one point,
100	  old userspace may exist which relies upon it, and as such this
101	  mechanism can never be removed from the kernel.
102
103	  You should only enable this functionality if you are certain you
104	  require a fallback mechanism and have a userspace mechanism ready to
105	  load firmware in case it is not found. One main reason for this may
106	  be if you have drivers which require firmware built-in and for
107	  whatever reason cannot place the required firmware in initramfs.
108	  Another reason kernels may have this feature enabled is to support a
109	  driver which explicitly relies on this fallback mechanism. Only two
110	  drivers need this today:
111
112	    o CONFIG_LEDS_LP55XX_COMMON
113	    o CONFIG_DELL_RBU
114
115	  Outside of supporting the above drivers, another reason for needing
116	  this may be that your firmware resides outside of the paths the kernel
117	  looks for and cannot possibly be specified using the firmware_class
118	  path module parameter or kernel firmware_class path boot parameter
119	  if firmware_class is built-in.
120
121	  A modern use case may be to temporarily mount a custom partition
122	  during provisioning which is only accessible to userspace, and then
123	  to use it to look for and fetch the required firmware. Such type of
124	  driver functionality may not even ever be desirable upstream by
125	  vendors, and as such is only required to be supported as an interface
126	  for provisioning. Since udev's firmware loading facility has been
127	  removed you can use firmwared or a fork of it to customize how you
128	  want to load firmware based on uevents issued.
129
130	  Enabling this option will increase your kernel image size by about
131	  13436 bytes.
132
133	  If you are unsure about this, say N here, unless you are Linux
134	  distribution and need to support the above two drivers, or you are
135	  certain you need to support some really custom firmware loading
136	  facility in userspace.
137
138config FW_LOADER_USER_HELPER_FALLBACK
139	bool "Force the firmware sysfs fallback mechanism when possible"
140	depends on FW_LOADER_USER_HELPER
141	help
142	  Enabling this option forces a sysfs userspace fallback mechanism
143	  to be used for all firmware requests which explicitly do not disable a
144	  a fallback mechanism. Firmware calls which do prohibit a fallback
145	  mechanism is request_firmware_direct(). This option is kept for
146          backward compatibility purposes given this precise mechanism can also
147	  be enabled by setting the proc sysctl value to true:
148
149	       /proc/sys/kernel/firmware_config/force_sysfs_fallback
150
151	  If you are unsure about this, say N here.
152
153endif # FW_LOADER
154endmenu
155