Kconfig (9256B)
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 27if FW_LOADER 28 29config FW_LOADER_PAGED_BUF 30 bool 31 32config FW_LOADER_SYSFS 33 bool 34 35config EXTRA_FIRMWARE 36 string "Build named firmware blobs into the kernel binary" 37 help 38 Device drivers which require firmware can typically deal with 39 having the kernel load firmware from the various supported 40 /lib/firmware/ paths. This option enables you to build into the 41 kernel firmware files. Built-in firmware searches are preceded 42 over firmware lookups using your filesystem over the supported 43 /lib/firmware paths documented on CONFIG_FW_LOADER. 44 45 This may be useful for testing or if the firmware is required early on 46 in boot and cannot rely on the firmware being placed in an initrd or 47 initramfs. 48 49 This option is a string and takes the (space-separated) names of the 50 firmware files -- the same names that appear in MODULE_FIRMWARE() 51 and request_firmware() in the source. These files should exist under 52 the directory specified by the EXTRA_FIRMWARE_DIR option, which is 53 /lib/firmware by default. 54 55 For example, you might set CONFIG_EXTRA_FIRMWARE="usb8388.bin", copy 56 the usb8388.bin file into /lib/firmware, and build the kernel. Then 57 any request_firmware("usb8388.bin") will be satisfied internally 58 inside the kernel without ever looking at your filesystem at runtime. 59 60 WARNING: If you include additional firmware files into your binary 61 kernel image that are not available under the terms of the GPL, 62 then it may be a violation of the GPL to distribute the resulting 63 image since it combines both GPL and non-GPL work. You should 64 consult a lawyer of your own before distributing such an image. 65 66 NOTE: Compressed files are not supported in EXTRA_FIRMWARE. 67 68config EXTRA_FIRMWARE_DIR 69 string "Firmware blobs root directory" 70 depends on EXTRA_FIRMWARE != "" 71 default "/lib/firmware" 72 help 73 This option controls the directory in which the kernel build system 74 looks for the firmware files listed in the EXTRA_FIRMWARE option. 75 76config FW_LOADER_USER_HELPER 77 bool "Enable the firmware sysfs fallback mechanism" 78 select FW_LOADER_SYSFS 79 select FW_LOADER_PAGED_BUF 80 help 81 This option enables a sysfs loading facility to enable firmware 82 loading to the kernel through userspace as a fallback mechanism 83 if and only if the kernel's direct filesystem lookup for the 84 firmware failed using the different /lib/firmware/ paths, or the 85 path specified in the firmware_class path module parameter, or the 86 firmware_class path kernel boot parameter if the firmware_class is 87 built-in. For details on how to work with the sysfs fallback mechanism 88 refer to Documentation/driver-api/firmware/fallback-mechanisms.rst. 89 90 The direct filesystem lookup for firmware is always used first now. 91 92 If the kernel's direct filesystem lookup for firmware fails to find 93 the requested firmware a sysfs fallback loading facility is made 94 available and userspace is informed about this through uevents. 95 The uevent can be suppressed if the driver explicitly requested it, 96 this is known as the driver using the custom fallback mechanism. 97 If the custom fallback mechanism is used userspace must always 98 acknowledge failure to find firmware as the timeout for the fallback 99 mechanism is disabled, and failed requests will linger forever. 100 101 This used to be the default firmware loading facility, and udev used 102 to listen for uvents to load firmware for the kernel. The firmware 103 loading facility functionality in udev has been removed, as such it 104 can no longer be relied upon as a fallback mechanism. Linux no longer 105 relies on or uses a fallback mechanism in userspace. If you need to 106 rely on one refer to the permissively licensed firmwared: 107 108 https://github.com/teg/firmwared 109 110 Since this was the default firmware loading facility at one point, 111 old userspace may exist which relies upon it, and as such this 112 mechanism can never be removed from the kernel. 113 114 You should only enable this functionality if you are certain you 115 require a fallback mechanism and have a userspace mechanism ready to 116 load firmware in case it is not found. One main reason for this may 117 be if you have drivers which require firmware built-in and for 118 whatever reason cannot place the required firmware in initramfs. 119 Another reason kernels may have this feature enabled is to support a 120 driver which explicitly relies on this fallback mechanism. Only two 121 drivers need this today: 122 123 o CONFIG_LEDS_LP55XX_COMMON 124 o CONFIG_DELL_RBU 125 126 Outside of supporting the above drivers, another reason for needing 127 this may be that your firmware resides outside of the paths the kernel 128 looks for and cannot possibly be specified using the firmware_class 129 path module parameter or kernel firmware_class path boot parameter 130 if firmware_class is built-in. 131 132 A modern use case may be to temporarily mount a custom partition 133 during provisioning which is only accessible to userspace, and then 134 to use it to look for and fetch the required firmware. Such type of 135 driver functionality may not even ever be desirable upstream by 136 vendors, and as such is only required to be supported as an interface 137 for provisioning. Since udev's firmware loading facility has been 138 removed you can use firmwared or a fork of it to customize how you 139 want to load firmware based on uevents issued. 140 141 Enabling this option will increase your kernel image size by about 142 13436 bytes. 143 144 If you are unsure about this, say N here, unless you are Linux 145 distribution and need to support the above two drivers, or you are 146 certain you need to support some really custom firmware loading 147 facility in userspace. 148 149config FW_LOADER_USER_HELPER_FALLBACK 150 bool "Force the firmware sysfs fallback mechanism when possible" 151 depends on FW_LOADER_USER_HELPER 152 help 153 Enabling this option forces a sysfs userspace fallback mechanism 154 to be used for all firmware requests which explicitly do not disable a 155 a fallback mechanism. Firmware calls which do prohibit a fallback 156 mechanism is request_firmware_direct(). This option is kept for 157 backward compatibility purposes given this precise mechanism can also 158 be enabled by setting the proc sysctl value to true: 159 160 /proc/sys/kernel/firmware_config/force_sysfs_fallback 161 162 If you are unsure about this, say N here. 163 164config FW_LOADER_COMPRESS 165 bool "Enable compressed firmware support" 166 help 167 This option enables the support for loading compressed firmware 168 files. The caller of firmware API receives the decompressed file 169 content. The compressed file is loaded as a fallback, only after 170 loading the raw file failed at first. 171 172 Compressed firmware support does not apply to firmware images 173 that are built into the kernel image (CONFIG_EXTRA_FIRMWARE). 174 175if FW_LOADER_COMPRESS 176config FW_LOADER_COMPRESS_XZ 177 bool "Enable XZ-compressed firmware support" 178 select FW_LOADER_PAGED_BUF 179 select XZ_DEC 180 default y 181 help 182 This option adds the support for XZ-compressed files. 183 The files have to be compressed with either none or crc32 184 integrity check type (pass "-C crc32" option to xz command). 185 186config FW_LOADER_COMPRESS_ZSTD 187 bool "Enable ZSTD-compressed firmware support" 188 select ZSTD_DECOMPRESS 189 help 190 This option adds the support for ZSTD-compressed files. 191 192endif # FW_LOADER_COMPRESS 193 194config FW_CACHE 195 bool "Enable firmware caching during suspend" 196 depends on PM_SLEEP 197 default y if PM_SLEEP 198 help 199 Because firmware caching generates uevent messages that are sent 200 over a netlink socket, it can prevent suspend on many platforms. 201 It is also not always useful, so on such platforms we have the 202 option. 203 204 If unsure, say Y. 205 206config FW_UPLOAD 207 bool "Enable users to initiate firmware updates using sysfs" 208 select FW_LOADER_SYSFS 209 select FW_LOADER_PAGED_BUF 210 help 211 Enabling this option will allow device drivers to expose a persistent 212 sysfs interface that allows firmware updates to be initiated from 213 userspace. For example, FPGA based PCIe cards load firmware and FPGA 214 images from local FLASH when the card boots. The images in FLASH may 215 be updated with new images provided by the user. Enable this device 216 to support cards that rely on user-initiated updates for firmware files. 217 218 If unsure, say N. 219 220endif # FW_LOADER 221endmenu