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firmware_loader: move kconfig FW_LOADER entries to its own file
This will make it easier to track and easier to understand what components and features are part of the FW_LOADER. There are some components related to firmware which have *nothing* to do with the FW_LOADER, souch as PREVENT_FIRMWARE_BUILD. Reviewed-by: Kees Cook <[email protected]> Signed-off-by: Luis R. Rodriguez <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
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| menu "Firmware loader" | ||
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| config FW_LOADER | ||
| tristate "Firmware loading facility" if EXPERT | ||
| default y | ||
| help | ||
| This enables the firmware loading facility in the kernel. The kernel | ||
| will first look for built-in firmware, if it has any. Next, it will | ||
| look for the requested firmware in a series of filesystem paths: | ||
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| o firmware_class path module parameter or kernel boot param | ||
| o /lib/firmware/updates/UTS_RELEASE | ||
| o /lib/firmware/updates | ||
| o /lib/firmware/UTS_RELEASE | ||
| o /lib/firmware | ||
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| Enabling this feature only increases your kernel image by about | ||
| 828 bytes, enable this option unless you are certain you don't | ||
| need firmware. | ||
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| You typically want this built-in (=y) but you can also enable this | ||
| as a module, in which case the firmware_class module will be built. | ||
| You also want to be sure to enable this built-in if you are going to | ||
| enable built-in firmware (CONFIG_EXTRA_FIRMWARE). | ||
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| if FW_LOADER | ||
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| config EXTRA_FIRMWARE | ||
| string "Build named firmware blobs into the kernel binary" | ||
| help | ||
| Device drivers which require firmware can typically deal with | ||
| having the kernel load firmware from the various supported | ||
| /lib/firmware/ paths. This option enables you to build into the | ||
| kernel firmware files. Built-in firmware searches are preceded | ||
| over firmware lookups using your filesystem over the supported | ||
| /lib/firmware paths documented on CONFIG_FW_LOADER. | ||
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| This may be useful for testing or if the firmware is required early on | ||
| in boot and cannot rely on the firmware being placed in an initrd or | ||
| initramfs. | ||
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| This option is a string and takes the (space-separated) names of the | ||
| firmware files -- the same names that appear in MODULE_FIRMWARE() | ||
| and request_firmware() in the source. These files should exist under | ||
| the directory specified by the EXTRA_FIRMWARE_DIR option, which is | ||
| /lib/firmware by default. | ||
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| For example, you might set CONFIG_EXTRA_FIRMWARE="usb8388.bin", copy | ||
| the usb8388.bin file into /lib/firmware, and build the kernel. Then | ||
| any request_firmware("usb8388.bin") will be satisfied internally | ||
| inside the kernel without ever looking at your filesystem at runtime. | ||
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| WARNING: If you include additional firmware files into your binary | ||
| kernel image that are not available under the terms of the GPL, | ||
| then it may be a violation of the GPL to distribute the resulting | ||
| image since it combines both GPL and non-GPL work. You should | ||
| consult a lawyer of your own before distributing such an image. | ||
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| config EXTRA_FIRMWARE_DIR | ||
| string "Firmware blobs root directory" | ||
| depends on EXTRA_FIRMWARE != "" | ||
| default "/lib/firmware" | ||
| help | ||
| This option controls the directory in which the kernel build system | ||
| looks for the firmware files listed in the EXTRA_FIRMWARE option. | ||
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| config FW_LOADER_USER_HELPER | ||
| bool "Enable the firmware sysfs fallback mechanism" | ||
| help | ||
| This option enables a sysfs loading facility to enable firmware | ||
| loading to the kernel through userspace as a fallback mechanism | ||
| if and only if the kernel's direct filesystem lookup for the | ||
| firmware failed using the different /lib/firmware/ paths, or the | ||
| path specified in the firmware_class path module parameter, or the | ||
| firmware_class path kernel boot parameter if the firmware_class is | ||
| built-in. For details on how to work with the sysfs fallback mechanism | ||
| refer to Documentation/driver-api/firmware/fallback-mechanisms.rst. | ||
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| The direct filesystem lookup for firmware is always used first now. | ||
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| If the kernel's direct filesystem lookup for firmware fails to find | ||
| the requested firmware a sysfs fallback loading facility is made | ||
| available and userspace is informed about this through uevents. | ||
| The uevent can be suppressed if the driver explicitly requested it, | ||
| this is known as the driver using the custom fallback mechanism. | ||
| If the custom fallback mechanism is used userspace must always | ||
| acknowledge failure to find firmware as the timeout for the fallback | ||
| mechanism is disabled, and failed requests will linger forever. | ||
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| This used to be the default firmware loading facility, and udev used | ||
| to listen for uvents to load firmware for the kernel. The firmware | ||
| loading facility functionality in udev has been removed, as such it | ||
| can no longer be relied upon as a fallback mechanism. Linux no longer | ||
| relies on or uses a fallback mechanism in userspace. If you need to | ||
| rely on one refer to the permissively licensed firmwared: | ||
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| https://github.com/teg/firmwared | ||
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| Since this was the default firmware loading facility at one point, | ||
| old userspace may exist which relies upon it, and as such this | ||
| mechanism can never be removed from the kernel. | ||
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| You should only enable this functionality if you are certain you | ||
| require a fallback mechanism and have a userspace mechanism ready to | ||
| load firmware in case it is not found. One main reason for this may | ||
| be if you have drivers which require firmware built-in and for | ||
| whatever reason cannot place the required firmware in initramfs. | ||
| Another reason kernels may have this feature enabled is to support a | ||
| driver which explicitly relies on this fallback mechanism. Only two | ||
| drivers need this today: | ||
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| o CONFIG_LEDS_LP55XX_COMMON | ||
| o CONFIG_DELL_RBU | ||
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| Outside of supporting the above drivers, another reason for needing | ||
| this may be that your firmware resides outside of the paths the kernel | ||
| looks for and cannot possibly be specified using the firmware_class | ||
| path module parameter or kernel firmware_class path boot parameter | ||
| if firmware_class is built-in. | ||
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| A modern use case may be to temporarily mount a custom partition | ||
| during provisioning which is only accessible to userspace, and then | ||
| to use it to look for and fetch the required firmware. Such type of | ||
| driver functionality may not even ever be desirable upstream by | ||
| vendors, and as such is only required to be supported as an interface | ||
| for provisioning. Since udev's firmware loading facility has been | ||
| removed you can use firmwared or a fork of it to customize how you | ||
| want to load firmware based on uevents issued. | ||
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| Enabling this option will increase your kernel image size by about | ||
| 13436 bytes. | ||
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| If you are unsure about this, say N here, unless you are Linux | ||
| distribution and need to support the above two drivers, or you are | ||
| certain you need to support some really custom firmware loading | ||
| facility in userspace. | ||
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| config FW_LOADER_USER_HELPER_FALLBACK | ||
| bool "Force the firmware sysfs fallback mechanism when possible" | ||
| depends on FW_LOADER_USER_HELPER | ||
| help | ||
| Enabling this option forces a sysfs userspace fallback mechanism | ||
| to be used for all firmware requests which explicitly do not disable a | ||
| a fallback mechanism. Firmware calls which do prohibit a fallback | ||
| mechanism is request_firmware_direct(). This option is kept for | ||
| backward compatibility purposes given this precise mechanism can also | ||
| be enabled by setting the proc sysctl value to true: | ||
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| /proc/sys/kernel/firmware_config/force_sysfs_fallback | ||
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| If you are unsure about this, say N here. | ||
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| endif # FW_LOADER | ||
| endmenu |