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