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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.
101 If a matching image is not already registered,
102 the firmware subsystem will try to load it using the
103 mechanisms specified below (typically, a kernel module
112 is made of the following functions:
114 .Fn firmware_register
115 registers with the kernel an image of size
122 The function returns NULL on error (e.g. because an
123 image with the same name already exists, or the image
125 .Ft const struct firmware *
126 pointer to the image requested.
128 .Fn firmware_unregister
129 tries to unregister the firmware image
132 The function is successful and returns 0
133 if there are no pending references to the image, otherwise
134 it does not unregister the image and returns EBUSY.
137 returns the requested firmware image.
138 If the image is not yet registered with the system,
139 the function tries to load it.
140 This involves the linker subsystem and disk access, so
142 must not be called with any locks (except for
144 Note also that if the firmware image is loaded from a filesystem
145 it must already be mounted.
146 In particular this means that it may be necessary to defer requests
147 from a driver attach method unless it is known the root filesystem is
152 returns a pointer to the image description and increases the reference count
154 On failure, the function returns NULL.
157 drops a reference to a firmware image.
160 argument may be set to
163 firmware_put is free to reclaim resources associated with
164 the firmware image if this is the last reference.
165 By default a firmware image will be deferred to a
167 thread so the call may be done while holding a lock.
168 In certain cases, such as on driver detach, this cannot be allowed.
169 .Sh FIRMWARE LOADING MECHANISMS
170 As mentioned before, any component of the system can register
171 firmware images at any time by simply calling
172 .Fn firmware_register .
174 This is typically done when a module containing
175 a firmware image is given control,
176 whether compiled in, or preloaded by
178 or manually loaded with
180 However, a system can implement additional mechanisms to bring
181 these images in memory before calling
182 .Fn firmware_register .
186 does not find the requested image, it tries to load it using
187 one of the available loading mechanisms.
188 At the moment, there is only one, namely
189 .Nm Loadable kernel modules :
191 A firmware image named
193 is looked up by trying to load the module named
195 using the facilities described in
197 In particular, images are looked up in the directories specified
198 by the sysctl variable
200 which on most systems defaults to
201 .Nm /boot/kernel;/boot/modules .
203 Note that in case a module contains multiple images,
204 the caller should first request a
206 for the first image contained in the module, followed by requests
207 for the other images.
208 .Sh BUILDING FIRMWARE LOADABLE MODULES
209 A firmware module is built by embedding the
211 into a suitable loadable kernel module that calls
212 .Fn firmware_register
214 .Fn firmware_unregister
217 Various system scripts and makefiles let you build a module
218 by simply writing a Makefile with the following entries:
222 FIRMWS= image_file:imagename[:version]
223 .include <bsd.kmod.mk>
226 where KMOD is the basename of the module; FIRMWS is a list of
227 colon-separated tuples indicating the image_file's to be embedded
228 in the module, the imagename and version of each firmware image.
230 If you need to embed firmware images into a system, you should write
231 appropriate entries in the <files.arch> file, e.g. this example is
233 .Nm sys/arm/xscale/ixp425/files.ixp425 :
235 ixp425_npe_fw.c optional npe_fw \\
236 compile-with "${AWK} -f $S/tools/fw_stub.awk \\
237 IxNpeMicrocode.dat:npe_fw -mnpe -c${.TARGET}" \\
238 no-implicit-rule before-depend local \\
239 clean "ixp425_npe_fw.c"
241 # NB: ld encodes the path in the binary symbols generated for the
242 # firmware image so link the file to the object directory to
243 # get known values for reference in the _fw.c file.
245 IxNpeMicrocode.fwo optional npe_fw \\
246 dependency "IxNpeMicrocode.dat" \\
247 compile-with "${LD} -b binary -d -warn-common \\
248 -r -d -o ${.TARGET} IxNpeMicrocode.dat" \\
250 clean "IxNpeMicrocode.fwo"
253 Firmware was previously committed to the source tree as uuencoded files,
254 but this is no longer required; the binary firmware file should be committed
255 to the tree as provided by the vendor.
257 Note that generating the firmware modules in this way requires
258 the availability of the following tools:
261 the compiler and the linker.
266 .Pa /usr/share/examples/kld/firmware
270 system was introduced in
273 This manual page was written by
274 .An Max Laier Aq Mt mlaier@FreeBSD.org .