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 <keescook@chromium.org>
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 154 insertions, 0 deletions

diff --git a/drivers/base/firmware_loader/Kconfig b/drivers/base/firmware_loader/Kconfig
new file mode 100644
index 000000000000..eb15d976a9ea
--- /dev/null
+++ b/drivers/base/firmware_loader/Kconfig
@@ -0,0 +1,154 @@
+menu "Firmware loader"
+
+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:
+
+		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
+
+	  Enabling this feature only increases your kernel image by about
+	  828 bytes, enable this option unless you are certain you don't
+	  need firmware.
+
+	  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).
+
+if FW_LOADER
+
+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.
+
+	  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.
+
+	  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.
+
+	  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.
+
+	  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.
+
+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.
+
+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.
+
+	  The direct filesystem lookup for firmware is always used first now.
+
+	  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.
+
+	  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:
+
+	  https://github.com/teg/firmwared
+
+	  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.
+
+	  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:
+
+	    o CONFIG_LEDS_LP55XX_COMMON
+	    o CONFIG_DELL_RBU
+
+	  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.
+
+	  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.
+
+	  Enabling this option will increase your kernel image size by about
+	  13436 bytes.
+
+	  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.
+
+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:
+
+	       /proc/sys/kernel/firmware_config/force_sysfs_fallback
+
+	  If you are unsure about this, say N here.
+
+endif # FW_LOADER
+endmenu