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Diffstat (limited to 'EmbeddedPkg/Drivers/FdtPlatformDxe/README.txt')
| -rw-r--r-- | EmbeddedPkg/Drivers/FdtPlatformDxe/README.txt | 72 |
1 files changed, 0 insertions, 72 deletions
diff --git a/EmbeddedPkg/Drivers/FdtPlatformDxe/README.txt b/EmbeddedPkg/Drivers/FdtPlatformDxe/README.txt deleted file mode 100644 index a87e7db28d..0000000000 --- a/EmbeddedPkg/Drivers/FdtPlatformDxe/README.txt +++ /dev/null @@ -1,72 +0,0 @@ -/** @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. |