273 lines
8.7 KiB
Groff
273 lines
8.7 KiB
Groff
.\" Copyright (c) 2006 Max Laier <mlaier@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd August 2, 2008
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.Dt FIRMWARE 9
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.Os
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.Sh NAME
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.Nm firmware_register ,
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.Nm firmware_unregister ,
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.Nm firmware_get ,
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.Nm firmware_put
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.Nd firmware image loading and management
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.Sh SYNOPSIS
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.In sys/param.h
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.In sys/systm.h
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.In sys/linker.h
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.In sys/firmware.h
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.Bd -literal
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struct firmware {
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const char *name; /* system-wide name */
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const void *data; /* location of image */
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size_t datasize; /* size of image in bytes */
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unsigned int version; /* version of the image */
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};
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.Ed
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.Ft "const struct firmware *"
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.Fo firmware_register
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.Fa "const char *imagename"
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.Fa "const void *data"
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.Fa "size_t datasize"
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.Fa "unsigned int version"
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.Fa "const struct firmware *parent"
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.Fc
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.Ft int
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.Fn firmware_unregister "const char *imagename"
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.Ft "const struct firmware *"
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.Fn firmware_get "const char *imagename"
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.Ft void
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.Fn firmware_put "const struct firmware *fp" "int flags"
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.Sh DESCRIPTION
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The
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.Nm firmware
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abstraction provides a convenient interface for loading
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.Nm firmware images
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into the kernel, and for accessing such images from kernel components.
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.Pp
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A
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.Nm firmware image
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(or
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.Nm image
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for brevity)
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is an opaque block of data residing in kernel memory.
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It is associated to a unique
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.Nm imagename
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which constitutes a search key, and to an integer
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.Nm version
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number, which is also an opaque piece of information for the
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firmware subsystem.
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.Pp
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An image is registered with the
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.Nm firmware
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subsystem by calling the function
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.Fn firmware_register ,
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and unregistered by calling
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.Fn firmware_unregister .
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These functions are usually (but not exclusively) called by
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specially crafted kernel modules that contain the firmware image.
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The modules can be statically compiled in the kernel, or loaded by
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.Nm /boot/loader ,
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manually at runtime, or on demand by the firmware subsystem.
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.Pp
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.Nm Clients
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of the firmware subsystem can request access to a given image
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by calling the function
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.Fn firmware_get
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with the
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.Nm imagename
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they want as an argument. If a matching image is not already registered,
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the firmware subsystem will try to load it using the
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mechanisms specified below (typically, a kernel module
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with
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.Nm
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the same name
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as the image).
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.Sh API DESCRIPTION
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The kernel
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.Nm
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firmware API
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is made of the following functions:
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.Pp
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.Fn firmware_register
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registers with the kernel an image of size
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.Nm datasize
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located at address
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.Nm data ,
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under the name
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.Nm imagename .
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.Pp
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The function returns NULL on error (e.g. because an
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image with the same name already exists, or the image
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table is full), or a
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.Ft const struct firmware *
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pointer to the image requested.
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.Pp
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.Fn firmware_unregister
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tries to unregister the firmware image
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.Nm imagename
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from the system. The function is successful and returns 0
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if there are no pending references to the image, otherwise
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it does not unregister the image and returns EBUSY.
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.Pp
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.Fn firmware_get
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returns the requested firmware image.
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If the image is not yet registered with the system,
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the function tries to load it.
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This involves the linker subsystem and disk access, so
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.Fn firmware_get
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must not be called with any locks (except for
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.Va Giant ) .
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Note also that if the firmware image is loaded from a filesystem
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it must already be mounted.
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In particular this means that it may be necessary to defer requests
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from a driver attach method unless it is known the root filesystem is
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already mounted.
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.Pp
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On success,
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.Fn firmware_get
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returns a pointer to the image description and increases the reference count
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for this image. On failure, the function returns NULL.
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.Pp
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.Fn firmware_put
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drops a reference to a firmware image.
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The
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.Fa flags
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argument may be set to
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.Dv FIRMWARE_UNLOAD
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to indicate that
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firmware_put is free to reclaim resources associated with
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the firmware image if this is the last reference.
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By default a firmware image will be deferred to a
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.Xr taskqueue 9
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thread so the call may be done while holding a lock.
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In certain cases, such as on driver detach, this cannot be allowed.
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.Sh FIRMWARE LOADING MECHANISMS
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As mentioned before, any component of the system can register
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firmware images at any time by simply calling
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.Fn firmware_register .
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.Pp
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This is typically done when a module containing
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a firmware image is given control,
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whether compiled in, or preloaded by
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.Nm /boot/loader ,
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or manually loaded with
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.Xr kldload 8 .
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However, a system can implement additional mechanisms to bring
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these images in memory before calling
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.Fn firmware_register .
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.Pp
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When
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.Fn firmware_get
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does not find the requested image, it tries to load it using
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one of the available loading mechanisms.
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At the moment, there is only one, namely
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.Nm Loadable kernel modules :
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.Pp
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A firmware image named
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.Nm foo
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is looked up by trying to load the module named
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.Nm foo.ko ,
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using the facilities described in
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.Xr kld 4 .
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In particular, images are looked up in the directories specified
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by the sysctl variable
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.Nm kern.module_path
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which on most systems defaults to
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.Nm /boot/kernel;/boot/modules .
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.Pp
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Note that in case a module contains multiple images,
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the caller should first request a
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.Fn firmware_get
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for the first image contained in the module, followed by requests
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for the other images.
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.Sh BUILDING FIRMWARE LOADABLE MODULES
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A firmware module is built by embedding the
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.Nm firmware image
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into a suitable loadable kernel module that calls
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.Fn firmware_register
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on loading, and
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.Fn firmware_unregister
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on unloading.
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.Pp
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Various system scripts and makefiles let you build a module
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by simply writing a Makefile with the following entries:
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.Bd -literal
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KMOD= imagename
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FIRMWS= image_file:imagename[:version]
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.include <bsd.kmod.mk>
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.Ed
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where KMOD is the basename of the module; FIRMWS is a list of
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colon-separated tuples indicating the image_file's to be embedded
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in the module, the imagename and version of each firmware image.
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.Pp
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If you need to embed firmware images into a system, you should write
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appropriate entries in the <files.arch> file, e.g. this example is
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from
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.Nm sys/arm/xscale/ixp425/files.ixp425 :
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.Bd -literal
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ixp425_npe_fw.c optional npe_fw \\
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compile-with "${AWK} -f $S/tools/fw_stub.awk \\
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IxNpeMicrocode.dat:npe_fw -mnpe -c${.TARGET}" \\
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no-implicit-rule before-depend local \\
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clean "ixp425_npe_fw.c"
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#
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# NB: ld encodes the path in the binary symbols generated for the
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# firmware image so link the file to the object directory to
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# get known values for reference in the _fw.c file.
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#
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IxNpeMicrocode.fwo optional npe_fw \\
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dependency "IxNpeMicrocode.dat" \\
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compile-with "${LD} -b binary -d -warn-common \\
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-r -d -o ${.TARGET} IxNpeMicrocode.dat" \\
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no-implicit-rule \\
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clean "IxNpeMicrocode.fwo"
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IxNpeMicrocode.dat optional npe_fw \\
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dependency ".PHONY" \\
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compile-with "uudecode < $S/contrib/dev/npe/IxNpeMicrocode.dat.uu" \\
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no-obj no-implicit-rule \\
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clean "IxNpeMicrocode.dat"
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.Ed
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.Pp
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Note that generating the firmware modules in this way requires
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the availability of the following tools:
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.Xr awk 1 ,
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.Xr make 1 ,
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the compiler and the linker.
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.Sh SEE ALSO
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.Xr kld 4 ,
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.Xr module 9
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.Pp
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.Pa /usr/share/examples/kld/firmware
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.Sh HISTORY
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The
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.Nm firmware
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system was introduced in
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.Fx 6.1 .
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.Sh AUTHORS
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This manual page was written by
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.An Max Laier Aq Mt mlaier@FreeBSD.org .
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