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24.\" $FreeBSD$ 25.\" 26.Dd March 14, 2019 27.Dt FIRMWARE 9 28.Os 29.Sh NAME 30.Nm firmware_register , 31.Nm firmware_unregister , 32.Nm firmware_get , 33.Nm firmware_put 34.Nd firmware image loading and management 35.Sh SYNOPSIS 36.In sys/param.h 37.In sys/systm.h 38.In sys/linker.h 39.In sys/firmware.h 40.Bd -literal 41struct firmware { 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 */ 46}; 47.Ed 48.Ft "const struct firmware *" 49.Fo firmware_register 50.Fa "const char *imagename" 51.Fa "const void *data" 52.Fa "size_t datasize" 53.Fa "unsigned int version" 54.Fa "const struct firmware *parent" 55.Fc 56.Ft int 57.Fn firmware_unregister "const char *imagename" 58.Ft "const struct firmware *" 59.Fn firmware_get "const char *imagename" 60.Ft void 61.Fn firmware_put "const struct firmware *fp" "int flags" 62.Sh DESCRIPTION 63The 64.Nm firmware 65abstraction provides a convenient interface for loading 66.Nm firmware images 67into the kernel, and for accessing such images from kernel components. 68.Pp 69A 70.Nm firmware image 71(or 72.Nm image 73for brevity) 74is an opaque block of data residing in kernel memory. 75It is associated to a unique 76.Nm imagename 77which constitutes a search key, and to an integer 78.Nm version 79number, which is also an opaque piece of information for the 80firmware subsystem. 81.Pp 82An image is registered with the 83.Nm firmware 84subsystem by calling the function 85.Fn firmware_register , 86and unregistered by calling 87.Fn firmware_unregister . 88These functions are usually (but not exclusively) called by 89specially crafted kernel modules that contain the firmware image. 90The modules can be statically compiled in the kernel, or loaded by 91.Nm /boot/loader , 92manually at runtime, or on demand by the firmware subsystem. 93.Pp 94.Nm Clients 95of the firmware subsystem can request access to a given image 96by calling the function 97.Fn firmware_get 98with the 99.Nm imagename 100they want as an argument. 101If a matching image is not already registered, 102the firmware subsystem will try to load it using the 103mechanisms specified below (typically, a kernel module 104with 105.Nm 106the same name 107as the image). 108.Sh API DESCRIPTION 109The kernel 110.Nm 111firmware API 112is made of the following functions: 113.Pp 114.Fn firmware_register 115registers with the kernel an image of size 116.Nm datasize 117located at address 118.Nm data , 119under the name 120.Nm imagename . 121.Pp 122The function returns NULL on error (e.g. because an 123image with the same name already exists, or the image 124table is full), or a 125.Ft const struct firmware * 126pointer to the image requested. 127.Pp 128.Fn firmware_unregister 129tries to unregister the firmware image 130.Nm imagename 131from the system. 132The function is successful and returns 0 133if there are no pending references to the image, otherwise 134it does not unregister the image and returns EBUSY. 135.Pp 136.Fn firmware_get 137returns the requested firmware image. 138If the image is not yet registered with the system, 139the function tries to load it. 140This involves the linker subsystem and disk access, so 141.Fn firmware_get 142must not be called with any locks (except for 143.Va Giant ) . 144Note also that if the firmware image is loaded from a filesystem 145it must already be mounted. 146In particular this means that it may be necessary to defer requests 147from a driver attach method unless it is known the root filesystem is 148already mounted. 149.Pp 150On success, 151.Fn firmware_get 152returns a pointer to the image description and increases the reference count 153for this image. 154On failure, the function returns NULL. 155.Pp 156.Fn firmware_put 157drops a reference to a firmware image. 158The 159.Fa flags 160argument may be set to 161.Dv FIRMWARE_UNLOAD 162to indicate that 163firmware_put is free to reclaim resources associated with 164the firmware image if this is the last reference. 165By default a firmware image will be deferred to a 166.Xr taskqueue 9 167thread so the call may be done while holding a lock. 168In certain cases, such as on driver detach, this cannot be allowed. 169.Sh FIRMWARE LOADING MECHANISMS 170As mentioned before, any component of the system can register 171firmware images at any time by simply calling 172.Fn firmware_register . 173.Pp 174This is typically done when a module containing 175a firmware image is given control, 176whether compiled in, or preloaded by 177.Nm /boot/loader , 178or manually loaded with 179.Xr kldload 8 . 180However, a system can implement additional mechanisms to bring 181these images in memory before calling 182.Fn firmware_register . 183.Pp 184When 185.Fn firmware_get 186does not find the requested image, it tries to load it using 187one of the available loading mechanisms. 188At the moment, there is only one, namely 189.Nm Loadable kernel modules : 190.Pp 191A firmware image named 192.Nm foo 193is looked up by trying to load the module named 194.Nm foo.ko , 195using the facilities described in 196.Xr kld 4 . 197In particular, images are looked up in the directories specified 198by the sysctl variable 199.Nm kern.module_path 200which on most systems defaults to 201.Nm /boot/kernel;/boot/modules . 202.Pp 203Note that in case a module contains multiple images, 204the caller should first request a 205.Fn firmware_get 206for the first image contained in the module, followed by requests 207for the other images. 208.Sh BUILDING FIRMWARE LOADABLE MODULES 209A firmware module is built by embedding the 210.Nm firmware image 211into a suitable loadable kernel module that calls 212.Fn firmware_register 213on loading, and 214.Fn firmware_unregister 215on unloading. 216.Pp 217Various system scripts and makefiles let you build a module 218by simply writing a Makefile with the following entries: 219.Bd -literal 220 221 KMOD= imagename 222 FIRMWS= image_file:imagename[:version] 223 .include <bsd.kmod.mk> 224 225.Ed 226where KMOD is the basename of the module; FIRMWS is a list of 227colon-separated tuples indicating the image_file's to be embedded 228in the module, the imagename and version of each firmware image. 229.Pp 230If you need to embed firmware images into a system, you should write 231appropriate entries in the <files.arch> file, e.g. this example is 232from 233.Nm sys/arm/xscale/ixp425/files.ixp425 : 234.Bd -literal 235ixp425_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" 240# 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. 244# 245IxNpeMicrocode.fwo optional npe_fw \\ 246 dependency "IxNpeMicrocode.dat" \\ 247 compile-with "${LD} -b binary -d -warn-common \\ 248 -r -d -o ${.TARGET} IxNpeMicrocode.dat" \\ 249 no-implicit-rule \\ 250 clean "IxNpeMicrocode.fwo" 251.Ed 252.Pp 253Firmware was previously committed to the source tree as uuencoded files, 254but this is no longer required; the binary firmware file should be committed 255to the tree as provided by the vendor. 256.Pp 257Note that generating the firmware modules in this way requires 258the availability of the following tools: 259.Xr awk 1 , 260.Xr make 1 , 261the compiler and the linker. 262.Sh SEE ALSO 263.Xr kld 4 , 264.Xr module 9 265.Pp 266.Pa /usr/share/examples/kld/firmware 267.Sh HISTORY 268The 269.Nm firmware 270system was introduced in 271.Fx 6.1 . 272.Sh AUTHORS 273This manual page was written by 274.An Max Laier Aq Mt mlaier@FreeBSD.org . 275