diff options
| author | Luis R. Rodriguez <mcgrof@kernel.org> | 2016-12-16 03:10:36 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-01-11 09:42:59 +0100 |
| commit | 113ccc38378b6f0b24c0993040c6044e35163a51 (patch) | |
| tree | 2a1fbd9a1ad5144dc316834ccf52505a84191cb3 /Documentation/driver-api/firmware/built-in-fw.rst | |
| parent | 880444e214cfd293a2e8cc4bd3505f7ffa6ce33a (diff) | |
firmware: revamp firmware documentation
Understanding this code is getting out of control without any
notes. Give the firmware_class driver a much needed documentation love,
and while at it convert it to the new sphinx documentation format.
v2: typos and small fixes
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation/driver-api/firmware/built-in-fw.rst')
| -rw-r--r-- | Documentation/driver-api/firmware/built-in-fw.rst | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/Documentation/driver-api/firmware/built-in-fw.rst b/Documentation/driver-api/firmware/built-in-fw.rst new file mode 100644 index 000000000000..7300e66857f8 --- /dev/null +++ b/Documentation/driver-api/firmware/built-in-fw.rst @@ -0,0 +1,38 @@ +================= +Built-in firmware +================= + +Firmware can be built-in to the kernel, this means building the firmware +into vmlinux directly, to enable avoiding having to look for firmware from +the filesystem. Instead, firmware can be looked for inside the kernel +directly. You can enable built-in firmware using the kernel configuration +options: + + * CONFIG_EXTRA_FIRMWARE + * CONFIG_EXTRA_FIRMWARE_DIR + +This should not be confused with CONFIG_FIRMWARE_IN_KERNEL, this is for drivers +which enables firmware to be built as part of the kernel build process. This +option, CONFIG_FIRMWARE_IN_KERNEL, will build all firmware for all drivers +enabled which ship its firmware inside the Linux kernel source tree. + +There are a few reasons why you might want to consider building your firmware +into the kernel with CONFIG_EXTRA_FIRMWARE though: + +* Speed +* Firmware is needed for accessing the boot device, and the user doesn't + want to stuff the firmware into the boot initramfs. + +Even if you have these needs there are a few reasons why you may not be +able to make use of built-in firmware: + +* Legalese - firmware is non-GPL compatible +* Some firmware may be optional +* Firmware upgrades are possible, therefore a new firmware would implicate + a complete kernel rebuild. +* Some firmware files may be really large in size. The remote-proc subsystem + is an example subsystem which deals with these sorts of firmware +* The firmware may need to be scraped out from some device specific location + dynamically, an example is calibration data for for some WiFi chipsets. This + calibration data can be unique per sold device. + |