1# SPDX-License-Identifier: GPL-2.0 2menu "Firmware loader" 3 4config FW_LOADER 5 tristate "Firmware loading facility" if EXPERT 6 select CRYPTO_HASH if FW_LOADER_DEBUG 7 select CRYPTO_SHA256 if FW_LOADER_DEBUG 8 default y 9 help 10 This enables the firmware loading facility in the kernel. The kernel 11 will first look for built-in firmware, if it has any. Next, it will 12 look for the requested firmware in a series of filesystem paths: 13 14 o firmware_class path module parameter or kernel boot param 15 o /lib/firmware/updates/UTS_RELEASE 16 o /lib/firmware/updates 17 o /lib/firmware/UTS_RELEASE 18 o /lib/firmware 19 20 Enabling this feature only increases your kernel image by about 21 828 bytes, enable this option unless you are certain you don't 22 need firmware. 23 24 You typically want this built-in (=y) but you can also enable this 25 as a module, in which case the firmware_class module will be built. 26 You also want to be sure to enable this built-in if you are going to 27 enable built-in firmware (CONFIG_EXTRA_FIRMWARE). 28 29config FW_LOADER_DEBUG 30 bool "Log filenames and checksums for loaded firmware" 31 depends on CRYPTO = FW_LOADER || CRYPTO=y 32 depends on DYNAMIC_DEBUG 33 depends on FW_LOADER 34 default FW_LOADER 35 help 36 Select this option to use dynamic debug to log firmware filenames and 37 SHA256 checksums to the kernel log for each firmware file that is 38 loaded. 39 40config RUST_FW_LOADER_ABSTRACTIONS 41 bool "Rust Firmware Loader abstractions" 42 depends on RUST 43 depends on FW_LOADER=y 44 help 45 This enables the Rust abstractions for the firmware loader API. 46 47if FW_LOADER 48 49config FW_LOADER_PAGED_BUF 50 bool 51 52config FW_LOADER_SYSFS 53 bool 54 55config EXTRA_FIRMWARE 56 string "Build named firmware blobs into the kernel binary" 57 help 58 Device drivers which require firmware can typically deal with 59 having the kernel load firmware from the various supported 60 /lib/firmware/ paths. This option enables you to build into the 61 kernel firmware files. Built-in firmware searches are preceded 62 over firmware lookups using your filesystem over the supported 63 /lib/firmware paths documented on CONFIG_FW_LOADER. 64 65 This may be useful for testing or if the firmware is required early on 66 in boot and cannot rely on the firmware being placed in an initrd or 67 initramfs. 68 69 This option is a string and takes the (space-separated) names of the 70 firmware files -- the same names that appear in MODULE_FIRMWARE() 71 and request_firmware() in the source. These files should exist under 72 the directory specified by the EXTRA_FIRMWARE_DIR option, which is 73 /lib/firmware by default. 74 75 For example, you might set CONFIG_EXTRA_FIRMWARE="usb8388.bin", copy 76 the usb8388.bin file into /lib/firmware, and build the kernel. Then 77 any request_firmware("usb8388.bin") will be satisfied internally 78 inside the kernel without ever looking at your filesystem at runtime. 79 80 WARNING: If you include additional firmware files into your binary 81 kernel image that are not available under the terms of the GPL, 82 then it may be a violation of the GPL to distribute the resulting 83 image since it combines both GPL and non-GPL work. You should 84 consult a lawyer of your own before distributing such an image. 85 86 NOTE: Compressed files are not supported in EXTRA_FIRMWARE. 87 88config EXTRA_FIRMWARE_DIR 89 string "Firmware blobs root directory" 90 depends on EXTRA_FIRMWARE != "" 91 default "/lib/firmware" 92 help 93 This option controls the directory in which the kernel build system 94 looks for the firmware files listed in the EXTRA_FIRMWARE option. 95 96config FW_LOADER_USER_HELPER 97 bool "Enable the firmware sysfs fallback mechanism" 98 select FW_LOADER_SYSFS 99 select FW_LOADER_PAGED_BUF 100 help 101 This option enables a sysfs loading facility to enable firmware 102 loading to the kernel through userspace as a fallback mechanism 103 if and only if the kernel's direct filesystem lookup for the 104 firmware failed using the different /lib/firmware/ paths, or the 105 path specified in the firmware_class path module parameter, or the 106 firmware_class path kernel boot parameter if the firmware_class is 107 built-in. For details on how to work with the sysfs fallback mechanism 108 refer to Documentation/driver-api/firmware/fallback-mechanisms.rst. 109 110 The direct filesystem lookup for firmware is always used first now. 111 112 If the kernel's direct filesystem lookup for firmware fails to find 113 the requested firmware a sysfs fallback loading facility is made 114 available and userspace is informed about this through uevents. 115 The uevent can be suppressed if the driver explicitly requested it, 116 this is known as the driver using the custom fallback mechanism. 117 If the custom fallback mechanism is used userspace must always 118 acknowledge failure to find firmware as the timeout for the fallback 119 mechanism is disabled, and failed requests will linger forever. 120 121 This used to be the default firmware loading facility, and udev used 122 to listen for uvents to load firmware for the kernel. The firmware 123 loading facility functionality in udev has been removed, as such it 124 can no longer be relied upon as a fallback mechanism. Linux no longer 125 relies on or uses a fallback mechanism in userspace. If you need to 126 rely on one refer to the permissively licensed firmwared: 127 128 https://github.com/teg/firmwared 129 130 Since this was the default firmware loading facility at one point, 131 old userspace may exist which relies upon it, and as such this 132 mechanism can never be removed from the kernel. 133 134 You should only enable this functionality if you are certain you 135 require a fallback mechanism and have a userspace mechanism ready to 136 load firmware in case it is not found. One main reason for this may 137 be if you have drivers which require firmware built-in and for 138 whatever reason cannot place the required firmware in initramfs. 139 Another reason kernels may have this feature enabled is to support a 140 driver which explicitly relies on this fallback mechanism. Only two 141 drivers need this today: 142 143 o CONFIG_LEDS_LP55XX_COMMON 144 o CONFIG_DELL_RBU 145 146 Outside of supporting the above drivers, another reason for needing 147 this may be that your firmware resides outside of the paths the kernel 148 looks for and cannot possibly be specified using the firmware_class 149 path module parameter or kernel firmware_class path boot parameter 150 if firmware_class is built-in. 151 152 A modern use case may be to temporarily mount a custom partition 153 during provisioning which is only accessible to userspace, and then 154 to use it to look for and fetch the required firmware. Such type of 155 driver functionality may not even ever be desirable upstream by 156 vendors, and as such is only required to be supported as an interface 157 for provisioning. Since udev's firmware loading facility has been 158 removed you can use firmwared or a fork of it to customize how you 159 want to load firmware based on uevents issued. 160 161 Enabling this option will increase your kernel image size by about 162 13436 bytes. 163 164 If you are unsure about this, say N here, unless you are Linux 165 distribution and need to support the above two drivers, or you are 166 certain you need to support some really custom firmware loading 167 facility in userspace. 168 169config FW_LOADER_USER_HELPER_FALLBACK 170 bool "Force the firmware sysfs fallback mechanism when possible" 171 depends on FW_LOADER_USER_HELPER 172 help 173 Enabling this option forces a sysfs userspace fallback mechanism 174 to be used for all firmware requests which explicitly do not disable a 175 a fallback mechanism. Firmware calls which do prohibit a fallback 176 mechanism is request_firmware_direct(). This option is kept for 177 backward compatibility purposes given this precise mechanism can also 178 be enabled by setting the proc sysctl value to true: 179 180 /proc/sys/kernel/firmware_config/force_sysfs_fallback 181 182 If you are unsure about this, say N here. 183 184config FW_LOADER_COMPRESS 185 bool "Enable compressed firmware support" 186 help 187 This option enables the support for loading compressed firmware 188 files. The caller of firmware API receives the decompressed file 189 content. The compressed file is loaded as a fallback, only after 190 loading the raw file failed at first. 191 192 Compressed firmware support does not apply to firmware images 193 that are built into the kernel image (CONFIG_EXTRA_FIRMWARE). 194 195if FW_LOADER_COMPRESS 196config FW_LOADER_COMPRESS_XZ 197 bool "Enable XZ-compressed firmware support" 198 select FW_LOADER_PAGED_BUF 199 select XZ_DEC 200 default y 201 help 202 This option adds the support for XZ-compressed files. 203 The files have to be compressed with either none or crc32 204 integrity check type (pass "-C crc32" option to xz command). 205 206config FW_LOADER_COMPRESS_ZSTD 207 bool "Enable ZSTD-compressed firmware support" 208 select ZSTD_DECOMPRESS 209 help 210 This option adds the support for ZSTD-compressed files. 211 212endif # FW_LOADER_COMPRESS 213 214config FW_CACHE 215 bool "Enable firmware caching during suspend" 216 depends on PM_SLEEP 217 default y if PM_SLEEP 218 help 219 Because firmware caching generates uevent messages that are sent 220 over a netlink socket, it can prevent suspend on many platforms. 221 It is also not always useful, so on such platforms we have the 222 option. 223 224 If unsure, say Y. 225 226config FW_UPLOAD 227 bool "Enable users to initiate firmware updates using sysfs" 228 select FW_LOADER_SYSFS 229 select FW_LOADER_PAGED_BUF 230 help 231 Enabling this option will allow device drivers to expose a persistent 232 sysfs interface that allows firmware updates to be initiated from 233 userspace. For example, FPGA based PCIe cards load firmware and FPGA 234 images from local FLASH when the card boots. The images in FLASH may 235 be updated with new images provided by the user. Enable this device 236 to support cards that rely on user-initiated updates for firmware files. 237 238 If unsure, say N. 239 240endif # FW_LOADER 241endmenu 242