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    Subject[PATCH v3 1/3] Documentation: arm: add UEFI support documentation
    Date
    This patch provides documentation of the [U]EFI runtime service and
    configuration features for the arm architecture.

    Changes since v1/v2:
    - Complete rewrite.
    - New FDT bindings.

    Cc: Rob Landley <rob@landley.net>
    Cc: linux-doc@vger.kernel.org

    Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
    ---
    Documentation/arm/00-INDEX | 3 +++
    Documentation/arm/uefi.txt | 61 ++++++++++++++++++++++++++++++++++++++++++++
    2 files changed, 64 insertions(+)
    create mode 100644 Documentation/arm/uefi.txt

    diff --git a/Documentation/arm/00-INDEX b/Documentation/arm/00-INDEX
    index 36420e1..b3af704 100644
    --- a/Documentation/arm/00-INDEX
    +++ b/Documentation/arm/00-INDEX
    @@ -34,3 +34,6 @@ nwfpe/
    - NWFPE floating point emulator documentation
    swp_emulation
    - SWP/SWPB emulation handler/logging description
    +
    +uefi.txt
    + - [U]EFI configuration and runtime services documentation
    diff --git a/Documentation/arm/uefi.txt b/Documentation/arm/uefi.txt
    new file mode 100644
    index 0000000..9ba59509
    --- /dev/null
    +++ b/Documentation/arm/uefi.txt
    @@ -0,0 +1,61 @@
    +UEFI, the Unified Extensible Firmware Interface is, a specification
    +governing the behaviours of compatible firmware interfaces. It is
    +maintained by the UEFI Forum - http://www.uefi.org/.
    +
    +UEFI is an evolution of its predecessor 'EFI', so the terms EFI and
    +UEFI are used somewhat interchangeably in this document and associated
    +source code. As a rule, anything new uses 'UEFI', whereas 'EFI' refers
    +to legacy code or specifications.
    +
    +UEFI support in Linux
    +=====================
    +Booting on a platform with firmware compliant with the UEFI specification
    +makes it possible for the kernel to support additional features:
    +- UEFI Runtime Services
    +- Retrieving various configuration information through the standardised
    + interface of UEFI configuration tables. (ACPI, SMBIOS, ...)
    +
    +For actually enabling [U]EFI support, enable:
    +- CONFIG_EFI=y
    +- CONFIG_EFI_VARS=y or m
    +
    +The implementation depends on receiving information about the UEFI environment
    +in a Flattened Device Tree (FDT) - so is only available with CONFIG_OF.
    +
    +UEFI stub
    +=========
    +The "stub" is a feature that turns the Image/zImage into a valid UEFI PE/COFF
    +executable, including a loader application that makes it possible to load the
    +kernel directly from the UEFI shell, boot menu, or one of the lightweight
    +bootloaders like Gummiboot or rEFInd.
    +
    +The kernel image built with stub support remains a valid kernel image for
    +booting in non-UEFI environments.
    +
    +UEFI kernel support on ARM
    +==========================
    +UEFI kernel support on the ARM architectures (arm and arm64) is only available
    +when boot is performed through the stub.
    +
    +The stub populates the FDT /chosen node with (and the kernel scans for) the
    +following parameters:
    +________________________________________________________________________________
    +Name | Size | Description
    +================================================================================
    +linux,uefi-system-table | 64-bit | Physical address of the UEFI System Table.
    +--------------------------------------------------------------------------------
    +linux,uefi-mmap-start | 64-bit | Physical address of the UEFI memory map,
    + | | populated by the UEFI GetMemoryMap() call.
    +--------------------------------------------------------------------------------
    +linux,uefi-mmap-size | 32-bit | Size in bytes of the UEFI memory map
    + | | pointed to in previous entry.
    +--------------------------------------------------------------------------------
    +linux,uefi-mmap-desc-size | 32-bit | Size in bytes of each entry in the UEFI
    + | | memory map.
    +--------------------------------------------------------------------------------
    +linux,uefi-mmap-desc-ver | 32-bit | Version of the mmap descriptor format.
    +--------------------------------------------------------------------------------
    +linux,uefi-stub-kern-ver | string | Copy of linux_banner from build.
    +--------------------------------------------------------------------------------
    +
    +For verbose debug messages, specify 'uefi_debug' on the kernel command line.
    --
    1.7.10.4


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