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