7d92da0eef
Add some information about this new bootmeth, including how to enable it and how it works. Series-to: concept Cover-letter: boot: Enhance VBE to support a separate devicetree FIT It is sometimes desirable to have the devicetrees packaged with firware, or in a different FIT from the OS. This series adds support for this, including a test. The new bootmeth can automatically locate a state file and use that to decide what images to use when booting. The OS must update the file before rebooting, if a different selection is required. For now there is no logic to deal with boot failures. END Signed-off-by: Simon Glass <sjg@chromium.org>
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30 lines
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.. SPDX-License-Identifier: GPL-2.0+
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Verified Boot for Embedded (VBE)
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================================
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Introduction
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------------
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VBE provides a standard boot mechanism for embedded systems. If defines
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how firmware and Operating Systems are located, updated and verified.
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Within U-Boot, one or more VBE bootmeths implement the boot logic. For example,
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the vbe-simple bootmeth handles finding the firmware (e.g. in MMC) and starting
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it. Typically the bootmeth is started up in VPL and controls which SPL and
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U-Boot binaries are loaded.
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A 'vbe' command provides access to various aspects of VBE's operation, including
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listing methods and getting the status for a method.
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For a detailed overview of VBE, see vbe-intro_. A fuller description of
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bootflows is at vbe-bootflows_ and the firmware-update mechanism is described at
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vbe-fwupdate_. VBE OS requests are described at vbe-osrequests_.
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See also :doc:`bootstd/vbe_os`.
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.. _vbe-intro: https://docs.google.com/document/d/e/2PACX-1vQjXLPWMIyVktaTMf8edHZYDrEvMYD_iNzIj1FgPmKF37fpglAC47Tt5cvPBC5fvTdoK-GA5Zv1wifo/pub
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.. _vbe-bootflows: https://docs.google.com/document/d/e/2PACX-1vR0OzhuyRJQ8kdeOibS3xB1rVFy3J4M_QKTM5-3vPIBNcdvR0W8EXu9ymG-yWfqthzWoM4JUNhqwydN/pub
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.. _vbe-fwupdate: https://docs.google.com/document/d/e/2PACX-1vTnlIL17vVbl6TVoTHWYMED0bme7oHHNk-g5VGxblbPiKIdGDALE1HKId8Go5f0g1eziLsv4h9bocbk/pub
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.. _vbe-osrequests: https://docs.google.com/document/d/e/2PACX-1vTHhxX7WSZe68i9rAkW-DHdx6koU-jxYHhamLhZn9GQ9QT2_epSBosMV1_r7yPHOXZccx71rF_t0PXL/pub
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