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24.\" $FreeBSD$ 25.\" 26.Dd January 27, 2021 27.Dt FIRMWARE 9 28.Os 29.Sh NAME 30.Nm firmware_register , 31.Nm firmware_unregister , 32.Nm firmware_get , 33.Nm firmware_get_flags , 34.Nm firmware_put 35.Nd firmware image loading and management 36.Sh SYNOPSIS 37.In sys/param.h 38.In sys/systm.h 39.In sys/linker.h 40.In sys/firmware.h 41.Bd -literal 42struct firmware { 43 const char *name; /* system-wide name */ 44 const void *data; /* location of image */ 45 size_t datasize; /* size of image in bytes */ 46 unsigned int version; /* version of the image */ 47}; 48.Ed 49.Ft "const struct firmware *" 50.Fo firmware_register 51.Fa "const char *imagename" 52.Fa "const void *data" 53.Fa "size_t datasize" 54.Fa "unsigned int version" 55.Fa "const struct firmware *parent" 56.Fc 57.Ft int 58.Fn firmware_unregister "const char *imagename" 59.Ft "const struct firmware *" 60.Fn firmware_get "const char *imagename" 61.Ft "const struct firmware *" 62.Fn firmware_get_flags "const char *imagename" "uint32_t flags" 63.Ft void 64.Fn firmware_put "const struct firmware *fp" "int flags" 65.Sh DESCRIPTION 66The 67.Nm firmware 68abstraction provides a convenient interface for loading 69.Nm firmware images 70into the kernel, and for accessing such images from kernel components. 71.Pp 72A 73.Nm firmware image 74(or 75.Nm image 76for brevity) 77is an opaque block of data residing in kernel memory. 78It is associated to a unique 79.Nm imagename 80which constitutes a search key, and to an integer 81.Nm version 82number, which is also an opaque piece of information for the 83firmware subsystem. 84.Pp 85An image is registered with the 86.Nm firmware 87subsystem by calling the function 88.Fn firmware_register , 89and unregistered by calling 90.Fn firmware_unregister . 91These functions are usually (but not exclusively) called by 92specially crafted kernel modules that contain the firmware image. 93The modules can be statically compiled in the kernel, or loaded by 94.Nm /boot/loader , 95manually at runtime, or on demand by the firmware subsystem. 96.Pp 97.Nm Clients 98of the firmware subsystem can request access to a given image 99by calling the function 100.Fn firmware_get 101with the 102.Nm imagename 103they want as an argument, or by calling 104.Fn firmware_get_flags 105with the 106.Nm imagename 107and 108.Nm flags 109they want as an arguments. 110If a matching image is not already registered, 111the firmware subsystem will try to load it using the 112mechanisms specified below (typically, a kernel module 113with 114.Nm 115the same name 116as the image). 117.Sh API DESCRIPTION 118The kernel 119.Nm 120firmware API 121is made of the following functions: 122.Pp 123.Fn firmware_register 124registers with the kernel an image of size 125.Nm datasize 126located at address 127.Nm data , 128under the name 129.Nm imagename . 130.Pp 131The function returns NULL on error (e.g. because an 132image with the same name already exists, or the image 133table is full), or a 134.Ft const struct firmware * 135pointer to the image requested. 136.Pp 137.Fn firmware_unregister 138tries to unregister the firmware image 139.Nm imagename 140from the system. 141The function is successful and returns 0 142if there are no pending references to the image, otherwise 143it does not unregister the image and returns EBUSY. 144.Pp 145.Fn firmware_get 146and 147.Fn firmware_get_flags 148return the requested firmware image. 149The 150.Fa flags 151argument may be set to 152.Dv FIRMWARE_GET_NOWARN 153to indicate that errors on firmware load or registration should 154only be logged in case of 155.Nm booverbose . 156If the image is not yet registered with the system, 157the functions try to load it. 158This involves the linker subsystem and disk access, so 159.Fn firmware_get 160or 161.Fn firmware_get_flags 162must not be called with any locks (except for 163.Va Giant ) . 164Note also that if the firmware image is loaded from a filesystem 165it must already be mounted. 166In particular this means that it may be necessary to defer requests 167from a driver attach method unless it is known the root filesystem is 168already mounted. 169.Pp 170On success, 171.Fn firmware_get 172and 173.Fn firmware_get_flags 174return a pointer to the image description and increase the reference count 175for this image. 176On failure, the functions return NULL. 177.Pp 178.Fn firmware_put 179drops a reference to a firmware image. 180The 181.Fa flags 182argument may be set to 183.Dv FIRMWARE_UNLOAD 184to indicate that 185firmware_put is free to reclaim resources associated with 186the firmware image if this is the last reference. 187By default a firmware image will be deferred to a 188.Xr taskqueue 9 189thread so the call may be done while holding a lock. 190In certain cases, such as on driver detach, this cannot be allowed. 191.Sh FIRMWARE LOADING MECHANISMS 192As mentioned before, any component of the system can register 193firmware images at any time by simply calling 194.Fn firmware_register . 195.Pp 196This is typically done when a module containing 197a firmware image is given control, 198whether compiled in, or preloaded by 199.Nm /boot/loader , 200or manually loaded with 201.Xr kldload 8 . 202However, a system can implement additional mechanisms to bring 203these images in memory before calling 204.Fn firmware_register . 205.Pp 206When 207.Fn firmware_get 208or 209.Fn firmware_get_flags 210does not find the requested image, it tries to load it using 211one of the available loading mechanisms. 212At the moment, there is only one, namely 213.Nm Loadable kernel modules . 214.Pp 215A firmware image named 216.Nm foo 217is looked up by trying to load the module named 218.Nm foo.ko , 219using the facilities described in 220.Xr kld 4 . 221In particular, images are looked up in the directories specified 222by the sysctl variable 223.Nm kern.module_path 224which on most systems defaults to 225.Nm /boot/kernel;/boot/modules . 226.Pp 227Note that in case a module contains multiple images, 228the caller should first request a 229.Fn firmware_get 230or 231.Fn firmware_get_flags 232for the first image contained in the module, followed by requests 233for the other images. 234.Sh BUILDING FIRMWARE LOADABLE MODULES 235A firmware module is built by embedding the 236.Nm firmware image 237into a suitable loadable kernel module that calls 238.Fn firmware_register 239on loading, and 240.Fn firmware_unregister 241on unloading. 242.Pp 243Various system scripts and makefiles let you build a module 244by simply writing a Makefile with the following entries: 245.Bd -literal 246 247 KMOD= imagename 248 FIRMWS= image_file:imagename[:version] 249 .include <bsd.kmod.mk> 250 251.Ed 252where KMOD is the basename of the module; FIRMWS is a list of 253colon-separated tuples indicating the image_file's to be embedded 254in the module, the imagename and version of each firmware image. 255.Pp 256If you need to embed firmware images into a system, you should write 257appropriate entries in the <files.arch> file, e.g. this example is 258from 259.Nm sys/arm/xscale/ixp425/files.ixp425 : 260.Bd -literal 261ixp425_npe_fw.c optional npe_fw \\ 262 compile-with "${AWK} -f $S/tools/fw_stub.awk \\ 263 IxNpeMicrocode.dat:npe_fw -mnpe -c${.TARGET}" \\ 264 no-implicit-rule before-depend local \\ 265 clean "ixp425_npe_fw.c" 266# 267# NB: ld encodes the path in the binary symbols generated for the 268# firmware image so link the file to the object directory to 269# get known values for reference in the _fw.c file. 270# 271IxNpeMicrocode.fwo optional npe_fw \\ 272 dependency "IxNpeMicrocode.dat" \\ 273 compile-with "${LD} -b binary -d -warn-common \\ 274 -r -d -o ${.TARGET} IxNpeMicrocode.dat" \\ 275 no-implicit-rule \\ 276 clean "IxNpeMicrocode.fwo" 277.Ed 278.Pp 279Firmware was previously committed to the source tree as uuencoded files, 280but this is no longer required; the binary firmware file should be committed 281to the tree as provided by the vendor. 282.Pp 283Note that generating the firmware modules in this way requires 284the availability of the following tools: 285.Xr awk 1 , 286.Xr make 1 , 287the compiler and the linker. 288.Sh SEE ALSO 289.Xr kld 4 , 290.Xr module 9 291.Pp 292.Pa /usr/share/examples/kld/firmware 293.Sh HISTORY 294The 295.Nm firmware 296system was introduced in 297.Fx 6.1 . 298.Sh AUTHORS 299This manual page was written by 300.An Max Laier Aq Mt mlaier@FreeBSD.org . 301