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30 .Nm firmware_register ,
31 .Nm firmware_unregister ,
34 .Nd firmware image loading and management
42 const char *name; /* system-wide name */
43 const void *data; /* location of image */
44 size_t datasize; /* size of image in bytes */
45 unsigned int version; /* version of the image */
48 .Ft "const struct firmware *"
50 .Fa "const char *imagename"
51 .Fa "const void *data"
53 .Fa "unsigned int version"
54 .Fa "const struct firmware *parent"
57 .Fn firmware_unregister "const char *imagename"
58 .Ft "const struct firmware *"
59 .Fn firmware_get "const char *imagename"
61 .Fn firmware_put "const struct firmware *fp" "int flags"
65 abstraction provides a convenient interface for loading
67 into the kernel, and for accessing such images from kernel components.
74 is an opaque block of data residing in kernel memory.
75 It is associated to a unique
77 which constitutes a search key, and to an integer
79 number, which is also an opaque piece of information for the
82 An image is registered with the
84 subsystem by calling the function
85 .Fn firmware_register ,
86 and unregistered by calling
87 .Fn firmware_unregister .
88 These functions are usually (but not exclusively) called by
89 specially crafted kernel modules that contain the firmware image.
90 The modules can be statically compiled in the kernel, or loaded by
92 manually at runtime, or on demand by the firmware subsystem.
95 of the firmware subsystem can request access to a given image
96 by calling the function
100 they want as an argument. If a matching image is not already registered,
101 the firmware subsystem will try to load it using the
102 mechanisms specified below (typically, a kernel module
109 is made of the following functions:
111 .Fn firmware_register
112 registers with the kernel an image of size
119 The function returns NULL on error (e.g. because an
120 image with the same name already exists, or the image
122 .Ft const struct firmware *
123 pointer to the image requested.
125 .Fn firmware_unregister
126 tries to unregister the firmware image
128 from the system. The function is successful and returns 0
129 if there are no pending references to the image, otherwise
130 it does not unregister the image and returns EBUSY.
133 returns the requested firmware image.
134 If the image is not yet registered with the system,
135 the function tries to load it.
136 This involves the linker subsystem and disk access, so
138 must not be called with any locks (except for
140 Note also that if the firmware image is loaded from a filesystem
141 it must already be mounted.
142 In particular this means that it may be necessary to defer requests
143 from a driver attach method unless it is known the root filesystem is
148 returns a pointer to the image description and increases the reference count
149 for this image. On failure, the function returns NULL.
152 drops a reference to a firmware image.
155 argument may be set to
158 firmware_put is free to reclaim resources associated with
159 the firmware image if this is the last reference.
160 By default a firmware image will be deferred to a
162 thread so the call may be done while holding a lock.
163 In certain cases, such as on driver detach, this cannot be allowed.
164 .Sh FIRMWARE LOADING MECHANISMS
165 As mentioned before, any component of the system can register
166 firmware images at any time by simply calling
167 .Fn firmware_register .
169 This is typically done when a module containing
170 a firmware image is given control,
171 whether compiled in, or preloaded by
173 or manually loaded with
175 However, a system can implement additional mechanisms to bring
176 these images in memory before calling
177 .Fn firmware_register .
181 does not find the requested image, it tries to load it using
182 one of the available loading mechanisms.
183 At the moment, there is only one, namely
184 .Nm Loadable kernel modules :
186 A firmware image named
188 is looked up by trying to load the module named
190 using the facilities described in
192 In particular, images are looked up in the directories specified
193 by the sysctl variable
195 which on most systems defaults to
196 .Nm /boot/kernel;/boot/modules .
198 Note that in case a module contains multiple images,
199 the caller should first request a
201 for the first image contained in the module, followed by requests
202 for the other images.
203 .Sh BUILDING FIRMWARE LOADABLE MODULES
204 A firmware module is built by embedding the
206 into a suitable loadable kernel module that calls
207 .Fn firmware_register
209 .Fn firmware_unregister
212 Various system scripts and makefiles let you build a module
213 by simply writing a Makefile with the following entries:
217 FIRMWS= image_file:imagename[:version]
218 .include <bsd.kmod.mk>
221 where KMOD is the basename of the module; FIRMWS is a list of
222 colon-separated tuples indicating the image_file's to be embedded
223 in the module, the imagename and version of each firmware image.
225 If you need to embed firmware images into a system, you should write
226 appropriate entries in the <files.arch> file, e.g. this example is
228 .Nm sys/arm/xscale/ixp425/files.ixp425:
230 ixp425_npe_fw.c optional npe_fw \\
231 compile-with "${AWK} -f $S/tools/fw_stub.awk \\
232 IxNpeMicrocode.dat:npe_fw -mnpe -c${.TARGET}" \\
233 no-implicit-rule before-depend local \\
234 clean "ixp425_npe_fw.c"
236 # NB: ld encodes the path in the binary symbols generated for the
237 # firmware image so link the file to the object directory to
238 # get known values for reference in the _fw.c file.
240 IxNpeMicrocode.fwo optional npe_fw \\
241 dependency "IxNpeMicrocode.dat" \\
242 compile-with "${LD} -b binary -d -warn-common \\
243 -r -d -o ${.TARGET} IxNpeMicrocode.dat" \\
245 clean "IxNpeMicrocode.fwo"
246 IxNpeMicrocode.dat optional npe_fw \\
247 dependency ".PHONY" \\
248 compile-with "uudecode < $S/contrib/dev/npe/IxNpeMicrocode.dat.uu" \\
249 no-obj no-implicit-rule \\
250 clean "IxNpeMicrocode.dat"
253 Note that generating the firmware modules in this way requires
254 the availability of the following tools:
257 the compiler and the linker.
262 .Pa /usr/share/examples/kld/firmware
266 system was introduced in
269 This manual page was written by
270 .An Max Laier Aq mlaier@FreeBSD.org .