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.
+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.
"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