+++ /dev/null
-/** @file
-
- Copyright (c) 2015, ARM Ltd. All rights reserved.<BR>
-
- This program and the accompanying materials
- are licensed and made available under the terms and conditions of the BSD License
- which accompanies this distribution. The full text of the license may be found at
- http://opensource.org/licenses/bsd-license.php
-
- THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
- WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
-
-**/
-
-The purpose of the FdtPlatformDxe UEFI driver is to install the Flat Device
-Tree (FDT) of the platform the UEFI frimware is running on into the UEFI
-Configuration Table. The FDT is identified within the UEFI Configuration
-Table by the "gFdtTableGuid" GUID defined in "EmbeddedPkg.dec".
-
-Once installed, an UEFI application or OS boot loader can get from the UEFI
-Configuration Table the FDT of the platform from the "gFdtTableGuid" GUID.
-
-The installation is done after each boot at the end of the DXE phase,
-just before the BDS phase. It is done at the end of the DXE phase to be sure
-that all drivers have been dispatched. That way, all UEFI protocols that may
-be needed to retrieve the FDT can be made available. It is done before the BDS
-phase to be able to provide the FDT during that phase.
-
-The present driver tries to retrieve the FDT from the device paths defined in the
-"gEmbeddedTokenSpaceGuid.PcdFdtDevicePaths" PCD. The "PcdFdtDevicePaths" PCD
-contains a list a device paths. The device paths are in the text form and
-separated by semi-colons. The present driver tries the device paths in the order
-it finds them in the "PcdFdtDevicePaths" PCD as long as he did not install
-succesfully a FDT.
-
-The "PcdFdtDevicePaths" PCD is a dynamic PCD that can be modified during the
-DXE phase. This allows for exemple to select the right FDT when a binary is
-intended to run on several platforms and/or variants of a platform.
-
-If the driver manages to download a FDT from one of the device paths mentioned
-above then it installs it in the UEFI Configuration table and the run over the
-device paths is stopped.
-
-For development purposes only, if the feature PCD "gEmbeddedTokenSpaceGuid.
-PcdOverridePlatformFdt" is equal to TRUE, then before to try to install the
-FDT from the device paths listed in the "PcdFdtDevicePaths" PCD, the present
-driver tries to install it using the device path defined by the UEFI variable
-"Fdt". If the variable does not exist or the installation using the device path
-defined by the UEFI variable fails then the installation proceeds as described
-above.
-
-Furthermore and again for development purposes only, if the feature PCD
-"PcdOverridePlatformFdt" is equal to TRUE, the current driver provides the EFI
-Shell command "setfdt" to define the location of the FDT by the mean of an EFI
-Shell file path (like "fs2:\boot\fdt.dtb") or a device path.
-
-If the path passed in to the command is a valid EFI Shell file path, the
-command translates it into the corresponding device path and stores that
-device path in the "Fdt" UEFI variable asking for the variable to be non
-volatile.
-
-If the path passed in to the command is not recognised as a valid EFI
-Shell device path, the command handles it as device path and stored
-in the "Fdt" UEFI variable as it is.
-
-Finally, the "-i" option of the "setfdt" command allows to trigger the FDT
-installation process. The installation process is completed when the command
-returns. The command can be invoked with the "-i" option only and in that
-case the "Fdt" UEFI variable is not updated and the command just runs the
-FDT installation process. If the command is invoked with the "-i" option and
-an EFI Shell file path then first the "Fdt" UEFI variable is updated accordingly
-and then the FDT installation process is run.
projects / mirror_edk2.git / blobdiff