--- name: "firmware" section: "9" platform: "freebsd" package: "base" version: "16.0-CURRENT-20261027-61c70dc16a79" release: "FreeBSD 16.0-CURRENT (2026-10-27)" platforms: ["freebsd"] url: "https://new.carta.tech/firmware" --- # firmware(9) firmware image loading and management ## NAME **firmware\_register**, **firmware\_unregister**, **firmware\_get**, **firmware\_get\_flags**, **firmware\_put** – firmware image loading and management ## SYNOPSIS **#include \** **#include \** **#include \** **#include \** ``` 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 */ }; ``` *const struct firmware \**\ **firmware\_register**(*const char \*imagename*, *const void \*data*, *size\_t datasize*, *unsigned int version*, *const struct firmware \*parent*); *int*\ **firmware\_unregister**(*const char \*imagename*); *const struct firmware \**\ **firmware\_get**(*const char \*imagename*); *const struct firmware \**\ **firmware\_get\_flags**(*const char \*imagename*, *uint32\_t flags*); *void*\ **firmware\_put**(*const struct firmware \*fp*, *int flags*); ## DESCRIPTION The **firmware** abstraction provides a convenient interface for loading **firmware** **images** into the kernel, and for accessing such images from kernel components. A **firmware** **image** (or **image** for brevity) is an opaque block of data residing in kernel memory. It is associated to a unique **imagename** which constitutes a search key, and to an integer **version** number, which is also an opaque piece of information for the firmware subsystem. An image is registered with the **firmware** subsystem by calling the function **firmware\_register**(), and unregistered by calling **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 */boot/loader*, manually at runtime, or on demand by the firmware subsystem. Firmware binary files may also be loaded directly rather than embedded into kernel modules. **Clients** of the firmware subsystem can request access to a given image by calling the function **firmware\_get**() with the **imagename** they want as an argument, or by calling **firmware\_get\_flags**() with the **imagename** and **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 **firmware\_register** the same name as the image). ## API DESCRIPTION The kernel **firmware\_register** firmware API is made of the following functions: **firmware\_register**() registers with the kernel an image of size **datasize** located at address **data**, under the name **imagename**. 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 *const* *struct* *firmware* *\** pointer to the image requested. **firmware\_unregister**() tries to unregister the firmware image **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. **firmware\_get**() and **firmware\_get\_flags**() return the requested firmware image. The *flags* argument may be set to FIRMWARE\_GET\_NOWARN to indicate that errors on firmware load or registration should only be logged in case of **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 **firmware\_get**() or **firmware\_get\_flags**() must not be called with any locks (except for *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. On success, **firmware\_get**() and **firmware\_get\_flags**() return a pointer to the image description and increase the reference count for this image. On failure, the functions return NULL. **firmware\_put**() drops a reference to a firmware image. The *flags* argument may be set to 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 [taskqueue(9)](/taskqueue/9.md) thread so the call may be done while holding a lock. In certain cases, such as on driver detach, this cannot be allowed. ## FIRMWARE LOADING VIA MODULES As mentioned before, any component of the system can register firmware images at any time by simply calling **firmware\_register**(). This is typically done when a module containing a firmware image is given control, whether compiled in, or preloaded by */boot/loader*, or manually loaded with [kldload(8)](/kldload/8.md). However, a system can implement additional mechanisms to bring these images into memory before calling **firmware\_register**(). When **firmware\_get**() or **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 **Loadable** **kernel** **modules**. A firmware image named **foo** is looked up by trying to load the module named **foo.ko**, using the facilities described in [kld(4)](/kld/4.md). In particular, images are looked up in the directories specified by the sysctl variable **kern.module\_path** which on most systems defaults to */boot/kernel;/boot/modules*. Note that in case a module contains multiple images, the caller should first request a **firmware\_get**() or **firmware\_get\_flags**() for the first image contained in the module, followed by requests for the other images. ## BUILDING FIRMWARE LOADABLE MODULES A firmware module is built by embedding the **firmware** **image** into a suitable loadable kernel module that calls **firmware\_register**() on loading, and **firmware\_unregister**() on unloading. Various system scripts and makefiles let you build a module by simply writing a Makefile with the following entries: ``` KMOD= imagename FIRMWS= image_file:imagename[:version] .include ``` 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. If you need to embed firmware images into a system, you should write appropriate entries in the \ or \ file, e.g. this example is from **sys/conf/files** ``` iwn1000fw.c optional iwn1000fw | iwnfw \ compile-with "${AWK} -f $S/tools/fw_stub.awk iwn1000.fw:iwn1000fw -miwn1000fw -c${.TARGET}" \ no-ctfconvert no-implicit-rule before-depend local \ clean "iwn1000fw.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. # iwn1000fw.fwo optional iwn1000fw | iwnfw \ dependency "iwn1000.fw" \ compile-with "${NORMAL_FWO}" \ no-implicit-rule \ clean "iwn1000fw.fwo" ``` 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. Note that generating the firmware modules in this way requires the availability of the following tools: [awk(1)](/awk/1.md), [make(1)](/make/1.md), the compiler and the linker. ## LOADING BINARY FIRMWARE FILES ### Binary Firmware Format Binary firmware files can also be loaded, either from */boot/loader*, or when **firmware\_get** cannot find the registered firmware from a kernel module. Binary firmware files are raw binary files that the creator of the firmware made. They offer an easier way to load firmware, but one that lacks the full flexibility and generality of kernel modules with the following restrictions: - Binary firmware files only hold one set of firmware. - They do not offer kernel module dependencies to ensure they are loaded automatically by the boot loader. - They cannot be compiled into the kernel. - The **imagename** is identical to the full path name used to load the module. - The version number is assumed to be zero. ### Loading from Pa /boot/loader Binary firmware files may be loaded either from the command line with “load -t firmware /boot/firmware/filename” or using the [loader.conf(5)](/loader.conf/5.md) mechanism to load modules with a type of “firmware” For example ``` wififw_load="YES" wififw_name="/boot/firmware/wifi2034_fw.bin" wififw_type="firmware" ``` ### On demand loading from Nm firmware\_get If no kernel module with an embedded firmware image named **imagename** is loaded, then **imagename** will be appended to the module path (by default */boot/firmware/*) and if that file exists, it will be loaded and registered using **firmware\_register** using the full path to the filename as **imagename**. ### Searching for imagename **firmware\_get** uses the following algorithm to find firmware images: - If an existing firmware image is registered for *imagename,* that image is returned. - If *imagename* matches the trailing subpath of a registered image with a full path, that image is returned. - The kernel linker searches for a kernel module named *imagename*. If a kernel module is found, it is loaded, and the list of registered firmware images is searched again. If a match is found, the matching image is returned. - The kernel searches for a file named *imagename* in the firmware image path (by default */boot/firmware/*). If that file exists and can be read, it contents are registered as a firmware image with the full path as the **imagename** and that firmware is returned. Currently, there is an 8MB limit on the size of the firmware image. This can be changed by by the sysctl variable **debug.max\_firmware\_size**. ## SEE ALSO [kld(4)](/kld/4.md), [module(9)](/module/9.md) */boot/firmware* */usr/share/examples/kld/firmware* ## HISTORY The **firmware** system was introduced in FreeBSD 6.1. Binary firmware loading was introduced in FreeBSD 15.0. ## AUTHORS This manual page was written by Max Laier ⟨*mlaier@FreeBSD.org*⟩.