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