1# SPDX-License-Identifier: GPL-2.0 2menu "Firmware loader" 3 4config FW_LOADER 5 tristate "Firmware loading facility" if EXPERT 6 select CRYPTO_LIB_SHA256 if FW_LOADER_DEBUG 7 default y 8 help 9 This enables the firmware loading facility in the kernel. The kernel 10 will first look for built-in firmware, if it has any. Next, it will 11 look for the requested firmware in a series of filesystem paths: 12 13 o firmware_class path module parameter or kernel boot param 14 o /lib/firmware/updates/UTS_RELEASE 15 o /lib/firmware/updates 16 o /lib/firmware/UTS_RELEASE 17 o /lib/firmware 18 19 Enabling this feature only increases your kernel image by about 20 828 bytes, enable this option unless you are certain you don't 21 need firmware. 22 23 You typically want this built-in (=y) but you can also enable this 24 as a module, in which case the firmware_class module will be built. 25 You also want to be sure to enable this built-in if you are going to 26 enable built-in firmware (CONFIG_EXTRA_FIRMWARE). 27 28config FW_LOADER_DEBUG 29 bool "Log filenames and checksums for loaded firmware" 30 depends on DYNAMIC_DEBUG 31 depends on FW_LOADER 32 default FW_LOADER 33 help 34 Select this option to use dynamic debug to log firmware filenames and 35 SHA256 checksums to the kernel log for each firmware file that is 36 loaded. 37 38config RUST_FW_LOADER_ABSTRACTIONS 39 bool "Rust Firmware Loader abstractions" 40 depends on RUST 41 depends on FW_LOADER=y 42 help 43 This enables the Rust abstractions for the firmware loader API. 44 45if FW_LOADER 46 47config FW_LOADER_PAGED_BUF 48 bool 49 50config FW_LOADER_SYSFS 51 bool 52 53config EXTRA_FIRMWARE 54 string "Build named firmware blobs into the kernel binary" 55 help 56 Device drivers which require firmware can typically deal with 57 having the kernel load firmware from the various supported 58 /lib/firmware/ paths. This option enables you to build into the 59 kernel firmware files. Built-in firmware searches are preceded 60 over firmware lookups using your filesystem over the supported 61 /lib/firmware paths documented on CONFIG_FW_LOADER. 62 63 This may be useful for testing or if the firmware is required early on 64 in boot and cannot rely on the firmware being placed in an initrd or 65 initramfs. 66 67 This option is a string and takes the (space-separated) names of the 68 firmware files -- the same names that appear in MODULE_FIRMWARE() 69 and request_firmware() in the source. These files should exist under 70 the directory specified by the EXTRA_FIRMWARE_DIR option, which is 71 /lib/firmware by default. 72 73 For example, you might set CONFIG_EXTRA_FIRMWARE="usb8388.bin", copy 74 the usb8388.bin file into /lib/firmware, and build the kernel. Then 75 any request_firmware("usb8388.bin") will be satisfied internally 76 inside the kernel without ever looking at your filesystem at runtime. 77 78 WARNING: If you include additional firmware files into your binary 79 kernel image that are not available under the terms of the GPL, 80 then it may be a violation of the GPL to distribute the resulting 81 image since it combines both GPL and non-GPL work. You should 82 consult a lawyer of your own before distributing such an image. 83 84 NOTE: Compressed files are not supported in EXTRA_FIRMWARE. 85 86config EXTRA_FIRMWARE_DIR 87 string "Firmware blobs root directory" 88 depends on EXTRA_FIRMWARE != "" 89 default "/lib/firmware" 90 help 91 This option controls the directory in which the kernel build system 92 looks for the firmware files listed in the EXTRA_FIRMWARE option. 93 94config FW_LOADER_USER_HELPER 95 bool "Enable the firmware sysfs fallback mechanism" 96 select FW_LOADER_SYSFS 97 select FW_LOADER_PAGED_BUF 98 help 99 This option enables a sysfs loading facility to enable firmware 100 loading to the kernel through userspace as a fallback mechanism 101 if and only if the kernel's direct filesystem lookup for the 102 firmware failed using the different /lib/firmware/ paths, or the 103 path specified in the firmware_class path module parameter, or the 104 firmware_class path kernel boot parameter if the firmware_class is 105 built-in. For details on how to work with the sysfs fallback mechanism 106 refer to Documentation/driver-api/firmware/fallback-mechanisms.rst. 107 108 The direct filesystem lookup for firmware is always used first now. 109 110 If the kernel's direct filesystem lookup for firmware fails to find 111 the requested firmware a sysfs fallback loading facility is made 112 available and userspace is informed about this through uevents. 113 The uevent can be suppressed if the driver explicitly requested it, 114 this is known as the driver using the custom fallback mechanism. 115 If the custom fallback mechanism is used userspace must always 116 acknowledge failure to find firmware as the timeout for the fallback 117 mechanism is disabled, and failed requests will linger forever. 118 119 This used to be the default firmware loading facility, and udev used 120 to listen for uvents to load firmware for the kernel. The firmware 121 loading facility functionality in udev has been removed, as such it 122 can no longer be relied upon as a fallback mechanism. Linux no longer 123 relies on or uses a fallback mechanism in userspace. If you need to 124 rely on one refer to the permissively licensed firmwared: 125 126 https://github.com/teg/firmwared 127 128 Since this was the default firmware loading facility at one point, 129 old userspace may exist which relies upon it, and as such this 130 mechanism can never be removed from the kernel. 131 132 You should only enable this functionality if you are certain you 133 require a fallback mechanism and have a userspace mechanism ready to 134 load firmware in case it is not found. One main reason for this may 135 be if you have drivers which require firmware built-in and for 136 whatever reason cannot place the required firmware in initramfs. 137 Another reason kernels may have this feature enabled is to support a 138 driver which explicitly relies on this fallback mechanism. Only two 139 drivers need this today: 140 141 o CONFIG_LEDS_LP55XX_COMMON 142 o CONFIG_DELL_RBU 143 144 Outside of supporting the above drivers, another reason for needing 145 this may be that your firmware resides outside of the paths the kernel 146 looks for and cannot possibly be specified using the firmware_class 147 path module parameter or kernel firmware_class path boot parameter 148 if firmware_class is built-in. 149 150 A modern use case may be to temporarily mount a custom partition 151 during provisioning which is only accessible to userspace, and then 152 to use it to look for and fetch the required firmware. Such type of 153 driver functionality may not even ever be desirable upstream by 154 vendors, and as such is only required to be supported as an interface 155 for provisioning. Since udev's firmware loading facility has been 156 removed you can use firmwared or a fork of it to customize how you 157 want to load firmware based on uevents issued. 158 159 Enabling this option will increase your kernel image size by about 160 13436 bytes. 161 162 If you are unsure about this, say N here, unless you are Linux 163 distribution and need to support the above two drivers, or you are 164 certain you need to support some really custom firmware loading 165 facility in userspace. 166 167config FW_LOADER_USER_HELPER_FALLBACK 168 bool "Force the firmware sysfs fallback mechanism when possible" 169 depends on FW_LOADER_USER_HELPER 170 help 171 Enabling this option forces a sysfs userspace fallback mechanism 172 to be used for all firmware requests which explicitly do not disable a 173 a fallback mechanism. Firmware calls which do prohibit a fallback 174 mechanism is request_firmware_direct(). This option is kept for 175 backward compatibility purposes given this precise mechanism can also 176 be enabled by setting the proc sysctl value to true: 177 178 /proc/sys/kernel/firmware_config/force_sysfs_fallback 179 180 If you are unsure about this, say N here. 181 182config FW_LOADER_COMPRESS 183 bool "Enable compressed firmware support" 184 help 185 This option enables the support for loading compressed firmware 186 files. The caller of firmware API receives the decompressed file 187 content. The compressed file is loaded as a fallback, only after 188 loading the raw file failed at first. 189 190 Compressed firmware support does not apply to firmware images 191 that are built into the kernel image (CONFIG_EXTRA_FIRMWARE). 192 193if FW_LOADER_COMPRESS 194config FW_LOADER_COMPRESS_XZ 195 bool "Enable XZ-compressed firmware support" 196 select FW_LOADER_PAGED_BUF 197 select XZ_DEC 198 default y 199 help 200 This option adds the support for XZ-compressed files. 201 The files have to be compressed with either none or crc32 202 integrity check type (pass "-C crc32" option to xz command). 203 204config FW_LOADER_COMPRESS_ZSTD 205 bool "Enable ZSTD-compressed firmware support" 206 select ZSTD_DECOMPRESS 207 help 208 This option adds the support for ZSTD-compressed files. 209 210endif # FW_LOADER_COMPRESS 211 212config FW_CACHE 213 bool "Enable firmware caching during suspend" 214 depends on PM_SLEEP 215 default y if PM_SLEEP 216 help 217 Because firmware caching generates uevent messages that are sent 218 over a netlink socket, it can prevent suspend on many platforms. 219 It is also not always useful, so on such platforms we have the 220 option. 221 222 If unsure, say Y. 223 224config FW_UPLOAD 225 bool "Enable users to initiate firmware updates using sysfs" 226 select FW_LOADER_SYSFS 227 select FW_LOADER_PAGED_BUF 228 help 229 Enabling this option will allow device drivers to expose a persistent 230 sysfs interface that allows firmware updates to be initiated from 231 userspace. For example, FPGA based PCIe cards load firmware and FPGA 232 images from local FLASH when the card boots. The images in FLASH may 233 be updated with new images provided by the user. Enable this device 234 to support cards that rely on user-initiated updates for firmware files. 235 236 If unsure, say N. 237 238endif # FW_LOADER 239endmenu 240