Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 52 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-firmware-ofw b/Documentation/ABI/testing/sysfs-firmware-ofw
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+What:		/sys/firmware/devicetree/*
+Date:		November 2013
+Contact:	Grant Likely <grant.likely@arm.com>, devicetree@vger.kernel.org
+Description:
+		When using OpenFirmware or a Flattened Device Tree to enumerate
+		hardware, the device tree structure will be exposed in this
+		directory.
+
+		It is possible for multiple device-tree directories to exist.
+		Some device drivers use a separate detached device tree which
+		have no attachment to the system tree and will appear in a
+		different subdirectory under /sys/firmware/devicetree.
+
+		Userspace must not use the /sys/firmware/devicetree/base
+		path directly, but instead should follow /proc/device-tree
+		symlink. It is possible that the absolute path will change
+		in the future, but the symlink is the stable ABI.
+
+		The /proc/device-tree symlink replaces the devicetree /proc
+		filesystem support, and has largely the same semantics and
+		should be compatible with existing userspace.
+
+		The contents of /sys/firmware/devicetree/ is a
+		hierarchy of directories, one per device tree node. The
+		directory name is the resolved path component name (node
+		name plus address). Properties are represented as files
+		in the directory. The contents of each file is the exact
+		binary data from the device tree.
+
+What:		/sys/firmware/fdt
+Date:		February 2015
+KernelVersion:	3.19
+Contact:	Frank Rowand <frowand.list@gmail.com>, devicetree@vger.kernel.org
+Description:
+		Exports the FDT blob that was passed to the kernel by
+		the bootloader. This allows userland applications such
+		as kexec to access the raw binary. This blob is also
+		useful when debugging since it contains any changes
+		made to the blob by the bootloader.
+
+		The fact that this node does not reside under
+		/sys/firmware/device-tree is deliberate: FDT is also used
+		on arm64 UEFI/ACPI systems to communicate just the UEFI
+		and ACPI entry points, but the FDT is never unflattened
+		and used to configure the system.
+
+		A CRC32 checksum is calculated over the entire FDT
+		blob, and verified at late_initcall time. The sysfs
+		entry is instantiated only if the checksum is valid,
+		i.e., if the FDT blob has not been modified in the mean
+		time. Otherwise, a warning is printed.
+Users:		kexec, debugging