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<!DOCTYPE html> <html class="writer-html5" lang="en" data-content_root="./"> <head> <meta charset="utf-8" /> <meta name="readthedocs-addons-api-version" content="1"><meta name="viewport" content="width=device-width, initial-scale=1" /> <meta name="viewport" content="width=device-width, initial-scale=1.0" /> <title>The U-Boot Documentation — Das U-Boot unknown version documentation</title> <link rel="stylesheet" href="_static/theme_overrides.css" type="text/css" /> <link rel="canonical" href="https://docs.u-boot.org/en/latest/index.html" /> <script src="_static/jquery.js?v=5d32c60e"></script> <script src="_static/_sphinx_javascript_frameworks_compat.js?v=2cd50e6c"></script> <script src="_static/documentation_options.js?v=44a24b83"></script> <script src="_static/doctools.js?v=9bcbadda"></script> <script src="_static/sphinx_highlight.js?v=dc90522c"></script> <script src="_static/js/theme.js"></script> <script src="_static/js/versions.js"></script> <link rel="index" title="Index" href="genindex.html" /> <link rel="search" title="Search" href="search.html" /> <link rel="next" title="Build U-Boot" href="build/index.html" /> <script async type="text/javascript" src="/_/static/javascript/readthedocs-addons.js"></script><meta name="readthedocs-project-slug" content="u-boot" /><meta name="readthedocs-version-slug" content="latest" /><meta name="readthedocs-resolver-filename" content="/" /><meta name="readthedocs-http-status" content="200" /></head> <body class="wy-body-for-nav"> <div class="wy-grid-for-nav"> <nav data-toggle="wy-nav-shift" class="wy-nav-side"> <div class="wy-side-scroll"> <div class="wy-side-nav-search" > <a href="#" class="icon icon-home"> Das U-Boot <img src="_static/u-boot_logo.svg" class="logo" alt="Logo"/> </a> <div class="switch-menus"> <div class="version-switch"></div> <div class="language-switch"></div> </div> <div role="search"> <form id="rtd-search-form" class="wy-form" action="search.html" method="get"> <input type="text" name="q" placeholder="Search docs" aria-label="Search docs" /> <input type="hidden" name="check_keywords" value="yes" /> <input type="hidden" name="area" value="default" /> </form> </div> </div><div class="wy-menu wy-menu-vertical" data-spy="affix" role="navigation" aria-label="Navigation menu"> <ul> <li class="toctree-l1"><a class="reference internal" href="build/index.html">Build U-Boot</a></li> <li class="toctree-l1"><a class="reference internal" href="learn/index.html">Learn about U-Boot</a></li> <li class="toctree-l1"><a class="reference internal" href="usage/index.html">Use U-Boot</a></li> </ul> <ul> <li class="toctree-l1"><a class="reference internal" href="develop/index.html">Develop U-Boot</a></li> </ul> <ul> <li class="toctree-l1"><a class="reference internal" href="api/index.html">U-Boot API documentation</a></li> </ul> <ul> <li class="toctree-l1"><a class="reference internal" href="arch/index.html">Architecture-specific doc</a></li> </ul> <ul> <li class="toctree-l1"><a class="reference internal" href="board/index.html">Board-specific doc</a></li> </ul> <ul> <li class="toctree-l1"><a class="reference internal" href="android/index.html">Android-specific doc</a></li> </ul> <ul> <li class="toctree-l1"><a class="reference internal" href="chromium/index.html">Chromium OS-specific doc</a></li> </ul> <ul> <li class="toctree-l1"><a class="reference internal" href="genindex.html">Index</a></li> </ul> </div> </div> </nav> <section data-toggle="wy-nav-shift" class="wy-nav-content-wrap"><nav class="wy-nav-top" aria-label="Mobile navigation menu" > <i data-toggle="wy-nav-top" class="fa fa-bars"></i> <a href="#">Das U-Boot</a> </nav> <div class="wy-nav-content"> <div class="rst-content"> <div role="navigation" aria-label="Page navigation"> <ul class="wy-breadcrumbs"> <li><a href="#" class="icon icon-home" aria-label="Home"></a></li> <li class="breadcrumb-item active">The U-Boot Documentation</li> <li class="wy-breadcrumbs-aside"> <a href="_sources/index.rst.txt" rel="nofollow"> View page source</a> </li> </ul> <hr/> </div> <div role="main" class="document" itemscope="itemscope" itemtype="http://schema.org/Article"> <div itemprop="articleBody"> <section id="the-u-boot-documentation"> <span id="u-boot-doc"></span><h1>The U-Boot Documentation<a class="headerlink" href="#the-u-boot-documentation" title="Link to this heading"></a></h1> <p>This is the top level of the U-Boot’s documentation tree. U-Boot documentation, like the U-Boot itself, is very much a work in progress; that is especially true as we work to integrate our many scattered documents into a coherent whole. Please note that improvements to the documentation are welcome; join the U-Boot list at <a class="reference external" href="http://lists.denx.de">http://lists.denx.de</a> if you want to help out.</p> <div class="toctree-wrapper compound"> </div> <section id="user-oriented-documentation"> <h2>User-oriented documentation<a class="headerlink" href="#user-oriented-documentation" title="Link to this heading"></a></h2> <p>The following manuals are written for <em>users</em> of the U-Boot - those who are trying to get it to work optimally on a given system.</p> <div class="toctree-wrapper compound"> <ul> <li class="toctree-l1"><a class="reference internal" href="build/index.html">Build U-Boot</a><ul> <li class="toctree-l2"><a class="reference internal" href="build/source.html">Obtaining the source</a></li> <li class="toctree-l2"><a class="reference internal" href="build/gcc.html">Building with GCC</a></li> <li class="toctree-l2"><a class="reference internal" href="build/clang.html">Building with Clang</a></li> <li class="toctree-l2"><a class="reference internal" href="build/reproducible.html">Reproducible builds</a></li> <li class="toctree-l2"><a class="reference internal" href="build/docker.html">GitLab CI / U-Boot runner container</a></li> <li class="toctree-l2"><a class="reference internal" href="build/tools.html">Host tools</a></li> <li class="toctree-l2"><a class="reference internal" href="build/buildman.html">Buildman build tool</a></li> <li class="toctree-l2"><a class="reference internal" href="build/documentation.html">Building documentation</a></li> <li class="toctree-l2"><a class="reference internal" href="build/gen_compile_commands.html">Create build database for IDEs</a></li> </ul> </li> <li class="toctree-l1"><a class="reference internal" href="learn/index.html">Learn about U-Boot</a><ul> <li class="toctree-l2"><a class="reference internal" href="learn/talks.html">U-Boot Talks</a></li> </ul> </li> <li class="toctree-l1"><a class="reference internal" href="usage/index.html">Use U-Boot</a><ul> <li class="toctree-l2"><a class="reference internal" href="usage/spl_boot.html">Booting from TPL/SPL</a></li> <li class="toctree-l2"><a class="reference internal" href="usage/blkmap.html">Block Maps (blkmap)</a></li> <li class="toctree-l2"><a class="reference internal" href="usage/dfu.html">Device Firmware Upgrade (DFU)</a></li> <li class="toctree-l2"><a class="reference internal" href="usage/environment.html">Environment Variables</a></li> <li class="toctree-l2"><a class="reference internal" href="usage/fdt_overlays.html">Device Tree Overlays</a></li> <li class="toctree-l2"><a class="reference internal" href="usage/fit/index.html">Flat Image Tree (FIT)</a></li> <li class="toctree-l2"><a class="reference internal" href="usage/netconsole.html">Network console</a></li> <li class="toctree-l2"><a class="reference internal" href="usage/partitions.html">Partitions</a></li> <li class="toctree-l2"><a class="reference internal" href="usage/cmdline.html">Command-line Parsing</a></li> <li class="toctree-l2"><a class="reference internal" href="usage/semihosting.html">Semihosting</a></li> <li class="toctree-l2"><a class="reference internal" href="usage/measured_boot.html">Measured Boot</a></li> <li class="toctree-l2"><a class="reference internal" href="usage/upl.html">Universal Payload</a></li> <li class="toctree-l2"><a class="reference internal" href="usage/index.html#shell-commands">Shell commands</a></li> <li class="toctree-l2"><a class="reference internal" href="usage/index.html#booting-os">Booting OS</a></li> </ul> </li> </ul> </div> </section> <section id="developer-oriented-documentation"> <h2>Developer-oriented documentation<a class="headerlink" href="#developer-oriented-documentation" title="Link to this heading"></a></h2> <p>The following manuals are written for <em>developers</em> of the U-Boot - those who want to contribute to U-Boot.</p> <div class="toctree-wrapper compound"> <ul> <li class="toctree-l1"><a class="reference internal" href="develop/index.html">Develop U-Boot</a><ul> <li class="toctree-l2"><a class="reference internal" href="develop/index.html#general">General</a></li> <li class="toctree-l2"><a class="reference internal" href="develop/index.html#implementation">Implementation</a></li> <li class="toctree-l2"><a class="reference internal" href="develop/index.html#debugging">Debugging</a></li> <li class="toctree-l2"><a class="reference internal" href="develop/index.html#packaging">Packaging</a></li> <li class="toctree-l2"><a class="reference internal" href="develop/index.html#testing">Testing</a></li> <li class="toctree-l2"><a class="reference internal" href="develop/index.html#refactoring">Refactoring</a></li> <li class="toctree-l2"><a class="reference internal" href="develop/index.html#code-quality">Code quality</a></li> <li class="toctree-l2"><a class="reference internal" href="develop/index.html#historical-documentation">Historical documentation</a></li> </ul> </li> </ul> </div> </section> <section id="u-boot-api-documentation"> <h2>U-Boot API documentation<a class="headerlink" href="#u-boot-api-documentation" title="Link to this heading"></a></h2> <p>These books get into the details of how specific U-Boot subsystems work from the point of view of a U-Boot developer. Much of the information here is taken directly from the U-Boot source, with supplemental material added as needed (or at least as we managed to add it - probably <em>not</em> all that is needed).</p> <div class="toctree-wrapper compound"> <ul> <li class="toctree-l1"><a class="reference internal" href="api/index.html">U-Boot API documentation</a><ul> <li class="toctree-l2"><a class="reference internal" href="api/bootcount.html">Boot Count Limit</a></li> <li class="toctree-l2"><a class="reference internal" href="api/clk.html">Clock API</a></li> <li class="toctree-l2"><a class="reference internal" href="api/dfu.html">Device firmware update</a></li> <li class="toctree-l2"><a class="reference internal" href="api/dm.html">Driver Model</a></li> <li class="toctree-l2"><a class="reference internal" href="api/efi.html">UEFI subsystem</a></li> <li class="toctree-l2"><a class="reference internal" href="api/event.html">Events</a></li> <li class="toctree-l2"><a class="reference internal" href="api/fs.html">File system API</a></li> <li class="toctree-l2"><a class="reference internal" href="api/getopt.html">Option Parsing</a></li> <li class="toctree-l2"><a class="reference internal" href="api/interrupt.html">Interrupt API</a></li> <li class="toctree-l2"><a class="reference internal" href="api/led.html">LED</a></li> <li class="toctree-l2"><a class="reference internal" href="api/linker_lists.html">Linker-Generated Arrays</a></li> <li class="toctree-l2"><a class="reference internal" href="api/lmb.html">Logical memory blocks</a></li> <li class="toctree-l2"><a class="reference internal" href="api/logging.html">Logging API</a></li> <li class="toctree-l2"><a class="reference internal" href="api/nvmem.html">NVMEM API</a></li> <li class="toctree-l2"><a class="reference internal" href="api/part.html">Partition API</a></li> <li class="toctree-l2"><a class="reference internal" href="api/pinctrl.html">Pinctrl and Pinmux</a></li> <li class="toctree-l2"><a class="reference internal" href="api/rng.html">Random number generation</a></li> <li class="toctree-l2"><a class="reference internal" href="api/sandbox.html">Sandbox</a></li> <li class="toctree-l2"><a class="reference internal" href="api/serial.html">Serial system</a></li> <li class="toctree-l2"><a class="reference internal" href="api/sysreset.html">System reset</a></li> <li class="toctree-l2"><a class="reference internal" href="api/timer.html">Timer Subsystem</a></li> <li class="toctree-l2"><a class="reference internal" href="api/unicode.html">Unicode support</a></li> </ul> </li> </ul> </div> </section> <section id="architecture-specific-doc"> <h2>Architecture-specific doc<a class="headerlink" href="#architecture-specific-doc" title="Link to this heading"></a></h2> <p>These books provide programming details about architecture-specific implementation.</p> <div class="toctree-wrapper compound"> <ul> <li class="toctree-l1"><a class="reference internal" href="arch/index.html">Architecture-specific doc</a><ul> <li class="toctree-l2"><a class="reference internal" href="arch/arc.html">ARC</a></li> <li class="toctree-l2"><a class="reference internal" href="arch/arm64.html">ARM64</a></li> <li class="toctree-l2"><a class="reference internal" href="arch/arm64.ffa.html">Arm FF-A Support</a></li> <li class="toctree-l2"><a class="reference internal" href="arch/m68k.html">M68K / ColdFire</a></li> <li class="toctree-l2"><a class="reference internal" href="arch/mips.html">MIPS</a></li> <li class="toctree-l2"><a class="reference internal" href="arch/nios2.html">Nios II</a></li> <li class="toctree-l2"><a class="reference internal" href="arch/riscv.html">RISC-V</a></li> <li class="toctree-l2"><a class="reference internal" href="arch/sandbox/index.html">Sandbox</a></li> <li class="toctree-l2"><a class="reference internal" href="arch/sh.html">SuperH</a></li> <li class="toctree-l2"><a class="reference internal" href="arch/x86/index.html">x86</a></li> <li class="toctree-l2"><a class="reference internal" href="arch/xtensa.html">Xtensa</a></li> </ul> </li> </ul> </div> </section> <section id="board-specific-doc"> <h2>Board-specific doc<a class="headerlink" href="#board-specific-doc" title="Link to this heading"></a></h2> <p>These books provide details about board-specific information. They are organized in a vendor subdirectory.</p> <div class="toctree-wrapper compound"> <ul> <li class="toctree-l1"><a class="reference internal" href="board/index.html">Board-specific doc</a><ul> <li class="toctree-l2"><a class="reference internal" href="board/actions/index.html">Actions</a></li> <li class="toctree-l2"><a class="reference internal" href="board/advantech/index.html">Advantech</a></li> <li class="toctree-l2"><a class="reference internal" href="board/andestech/index.html">Andes Tech</a></li> <li class="toctree-l2"><a class="reference internal" href="board/allwinner/index.html">Allwinner (sunxi) boards</a></li> <li class="toctree-l2"><a class="reference internal" href="board/amlogic/index.html">Amlogic</a></li> <li class="toctree-l2"><a class="reference internal" href="board/anbernic/index.html">Anbernic</a></li> <li class="toctree-l2"><a class="reference internal" href="board/apple/index.html">Apple</a></li> <li class="toctree-l2"><a class="reference internal" 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href="board/phytec/index.html">PHYTEC</a></li> <li class="toctree-l2"><a class="reference internal" href="board/purism/index.html">Purism SPC</a></li> <li class="toctree-l2"><a class="reference internal" href="board/qualcomm/index.html">Qualcomm</a></li> <li class="toctree-l2"><a class="reference internal" href="board/qnap/index.html">Qnap</a></li> <li class="toctree-l2"><a class="reference internal" href="board/renesas/index.html">Renesas</a></li> <li class="toctree-l2"><a class="reference internal" href="board/rockchip/index.html">Rockchip</a></li> <li class="toctree-l2"><a class="reference internal" href="board/samsung/index.html">Samsung</a></li> <li class="toctree-l2"><a class="reference internal" href="board/schneider/index.html">Schneider Electric</a></li> <li class="toctree-l2"><a class="reference internal" href="board/sielaff/index.html">Sielaff</a></li> <li class="toctree-l2"><a class="reference internal" href="board/siemens/index.html">Siemens</a></li> <li class="toctree-l2"><a class="reference internal" href="board/sifive/index.html">SiFive</a></li> <li class="toctree-l2"><a class="reference internal" href="board/sipeed/index.html">Sipeed</a></li> <li class="toctree-l2"><a class="reference internal" href="board/socionext/index.html">Socionext</a></li> <li class="toctree-l2"><a class="reference internal" href="board/sophgo/index.html">Sophgo</a></li> <li class="toctree-l2"><a class="reference internal" href="board/spacemit/index.html">SpacemiT</a></li> <li class="toctree-l2"><a class="reference internal" href="board/st/index.html">STMicroelectronics</a></li> <li class="toctree-l2"><a class="reference internal" href="board/starfive/index.html">StarFive</a></li> <li class="toctree-l2"><a class="reference internal" href="board/ste/index.html">ST-Ericsson</a></li> <li class="toctree-l2"><a class="reference internal" href="board/tbs/index.html">TBS</a></li> <li class="toctree-l2"><a class="reference internal" href="board/thead/index.html">T-HEAD</a></li> <li class="toctree-l2"><a class="reference internal" href="board/theobroma-systems/index.html">Theobroma Systems</a></li> <li class="toctree-l2"><a class="reference internal" href="board/ti/index.html">Texas Instruments</a></li> <li class="toctree-l2"><a class="reference internal" href="board/toradex/index.html">Toradex</a></li> <li class="toctree-l2"><a class="reference internal" href="board/variscite/index.html">Variscite</a></li> <li class="toctree-l2"><a class="reference internal" href="board/wexler/index.html">WEXLER</a></li> <li class="toctree-l2"><a class="reference internal" href="board/xen/index.html">XenGuestARM64</a></li> <li class="toctree-l2"><a class="reference internal" href="board/xilinx/index.html">Xilinx</a></li> </ul> </li> </ul> </div> </section> <section id="android-specific-doc"> <h2>Android-specific doc<a class="headerlink" href="#android-specific-doc" title="Link to this heading"></a></h2> <p>These books provide information about booting the Android OS from U-Boot, manipulating Android images from U-Boot shell and discusses other Android-specific features available in U-Boot.</p> <div class="toctree-wrapper compound"> <ul> <li class="toctree-l1"><a class="reference internal" href="android/index.html">Android-specific doc</a><ul> <li class="toctree-l2"><a class="reference internal" href="android/ab.html">Android A/B updates</a></li> <li class="toctree-l2"><a class="reference internal" href="android/avb2.html">Android Verified Boot 2.0</a></li> <li class="toctree-l2"><a class="reference internal" href="android/bcb.html">Android Bootloader Control Block (BCB)</a></li> <li class="toctree-l2"><a class="reference internal" href="android/boot-image.html">Android Boot Image</a></li> <li class="toctree-l2"><a class="reference internal" href="android/fastboot-protocol.html">FastBoot Version 0.4</a></li> <li class="toctree-l2"><a class="reference internal" href="android/fastboot.html">Android Fastboot</a></li> </ul> </li> </ul> </div> </section> <section id="chromium-os-specific-doc"> <h2>Chromium OS-specific doc<a class="headerlink" href="#chromium-os-specific-doc" title="Link to this heading"></a></h2> <div class="toctree-wrapper compound"> <ul> <li class="toctree-l1"><a class="reference internal" href="chromium/index.html">Chromium OS-specific doc</a><ul> <li class="toctree-l2"><a class="reference internal" href="chromium/overview.html">Chromium OS Support in U-Boot</a></li> <li class="toctree-l2"><a class="reference internal" href="chromium/run_vboot.html">Running U-Boot with Chromium OS verified boot</a></li> <li class="toctree-l2"><a class="reference internal" href="chromium/chainload.html">Running U-Boot from coreboot on Chromebooks</a></li> </ul> </li> </ul> </div> </section> </section> <section id="indices-and-tables"> <h1>Indices and tables<a class="headerlink" href="#indices-and-tables" title="Link to this heading"></a></h1> <div class="toctree-wrapper 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