.\" Copyright (c) 2006 Max Laier .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. .\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd January 27, 2021 .Dt FIRMWARE 9 .Os .Sh NAME .Nm firmware_register , .Nm firmware_unregister , .Nm firmware_get , .Nm firmware_get_flags , .Nm firmware_put .Nd firmware image loading and management .Sh SYNOPSIS .In sys/param.h .In sys/systm.h .In sys/linker.h .In sys/firmware.h .Bd -literal struct firmware { const char *name; /* system-wide name */ const void *data; /* location of image */ size_t datasize; /* size of image in bytes */ unsigned int version; /* version of the image */ }; .Ed .Ft "const struct firmware *" .Fo firmware_register .Fa "const char *imagename" .Fa "const void *data" .Fa "size_t datasize" .Fa "unsigned int version" .Fa "const struct firmware *parent" .Fc .Ft int .Fn firmware_unregister "const char *imagename" .Ft "const struct firmware *" .Fn firmware_get "const char *imagename" .Ft "const struct firmware *" .Fn firmware_get_flags "const char *imagename" "uint32_t flags" .Ft void .Fn firmware_put "const struct firmware *fp" "int flags" .Sh DESCRIPTION The .Nm firmware abstraction provides a convenient interface for loading .Nm firmware images into the kernel, and for accessing such images from kernel components. .Pp A .Nm firmware image (or .Nm image for brevity) is an opaque block of data residing in kernel memory. It is associated to a unique .Nm imagename which constitutes a search key, and to an integer .Nm version number, which is also an opaque piece of information for the firmware subsystem. .Pp An image is registered with the .Nm firmware subsystem by calling the function .Fn firmware_register , and unregistered by calling .Fn firmware_unregister . These functions are usually (but not exclusively) called by specially crafted kernel modules that contain the firmware image. The modules can be statically compiled in the kernel, or loaded by .Nm /boot/loader , manually at runtime, or on demand by the firmware subsystem. .Pp .Nm Clients of the firmware subsystem can request access to a given image by calling the function .Fn firmware_get with the .Nm imagename they want as an argument, or by calling .Fn firmware_get_flags with the .Nm imagename and .Nm flags they want as an arguments. If a matching image is not already registered, the firmware subsystem will try to load it using the mechanisms specified below (typically, a kernel module with .Nm the same name as the image). .Sh API DESCRIPTION The kernel .Nm firmware API is made of the following functions: .Pp .Fn firmware_register registers with the kernel an image of size .Nm datasize located at address .Nm data , under the name .Nm imagename . .Pp The function returns NULL on error (e.g. because an image with the same name already exists, or the image table is full), or a .Ft const struct firmware * pointer to the image requested. .Pp .Fn firmware_unregister tries to unregister the firmware image .Nm imagename from the system. The function is successful and returns 0 if there are no pending references to the image, otherwise it does not unregister the image and returns EBUSY. .Pp .Fn firmware_get and .Fn firmware_get_flags return the requested firmware image. The .Fa flags argument may be set to .Dv FIRMWARE_GET_NOWARN to indicate that errors on firmware load or registration should only be logged in case of .Nm booverbose . If the image is not yet registered with the system, the functions try to load it. This involves the linker subsystem and disk access, so .Fn firmware_get or .Fn firmware_get_flags must not be called with any locks (except for .Va Giant ) . Note also that if the firmware image is loaded from a filesystem it must already be mounted. In particular this means that it may be necessary to defer requests from a driver attach method unless it is known the root filesystem is already mounted. .Pp On success, .Fn firmware_get and .Fn firmware_get_flags return a pointer to the image description and increase the reference count for this image. On failure, the functions return NULL. .Pp .Fn firmware_put drops a reference to a firmware image. The .Fa flags argument may be set to .Dv FIRMWARE_UNLOAD to indicate that firmware_put is free to reclaim resources associated with the firmware image if this is the last reference. By default a firmware image will be deferred to a .Xr taskqueue 9 thread so the call may be done while holding a lock. In certain cases, such as on driver detach, this cannot be allowed. .Sh FIRMWARE LOADING MECHANISMS As mentioned before, any component of the system can register firmware images at any time by simply calling .Fn firmware_register . .Pp This is typically done when a module containing a firmware image is given control, whether compiled in, or preloaded by .Nm /boot/loader , or manually loaded with .Xr kldload 8 . However, a system can implement additional mechanisms to bring these images in memory before calling .Fn firmware_register . .Pp When .Fn firmware_get or .Fn firmware_get_flags does not find the requested image, it tries to load it using one of the available loading mechanisms. At the moment, there is only one, namely .Nm Loadable kernel modules . .Pp A firmware image named .Nm foo is looked up by trying to load the module named .Nm foo.ko , using the facilities described in .Xr kld 4 . In particular, images are looked up in the directories specified by the sysctl variable .Nm kern.module_path which on most systems defaults to .Nm /boot/kernel;/boot/modules . .Pp Note that in case a module contains multiple images, the caller should first request a .Fn firmware_get or .Fn firmware_get_flags for the first image contained in the module, followed by requests for the other images. .Sh BUILDING FIRMWARE LOADABLE MODULES A firmware module is built by embedding the .Nm firmware image into a suitable loadable kernel module that calls .Fn firmware_register on loading, and .Fn firmware_unregister on unloading. .Pp Various system scripts and makefiles let you build a module by simply writing a Makefile with the following entries: .Bd -literal KMOD= imagename FIRMWS= image_file:imagename[:version] .include .Ed where KMOD is the basename of the module; FIRMWS is a list of colon-separated tuples indicating the image_file's to be embedded in the module, the imagename and version of each firmware image. .Pp If you need to embed firmware images into a system, you should write appropriate entries in the file, e.g. this example is from .Nm sys/arm/xscale/ixp425/files.ixp425 : .Bd -literal ixp425_npe_fw.c optional npe_fw \\ compile-with "${AWK} -f $S/tools/fw_stub.awk \\ IxNpeMicrocode.dat:npe_fw -mnpe -c${.TARGET}" \\ no-implicit-rule before-depend local \\ clean "ixp425_npe_fw.c" # # NB: ld encodes the path in the binary symbols generated for the # firmware image so link the file to the object directory to # get known values for reference in the _fw.c file. # IxNpeMicrocode.fwo optional npe_fw \\ dependency "IxNpeMicrocode.dat" \\ compile-with "${LD} -b binary -d -warn-common \\ -r -d -o ${.TARGET} IxNpeMicrocode.dat" \\ no-implicit-rule \\ clean "IxNpeMicrocode.fwo" .Ed .Pp Firmware was previously committed to the source tree as uuencoded files, but this is no longer required; the binary firmware file should be committed to the tree as provided by the vendor. .Pp Note that generating the firmware modules in this way requires the availability of the following tools: .Xr awk 1 , .Xr make 1 , the compiler and the linker. .Sh SEE ALSO .Xr kld 4 , .Xr module 9 .Pp .Pa /usr/share/examples/kld/firmware .Sh HISTORY The .Nm firmware system was introduced in .Fx 6.1 . .Sh AUTHORS This manual page was written by .An Max Laier Aq Mt mlaier@FreeBSD.org .