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This adds the "iommu-addresses" property to reserved-memory nodes, which
allow describing the interaction of memory regions with IOMMUs. Two use-
cases are supported:
1. Static mappings can be described by pairing the "iommu-addresses"
property with a "reg" property. This is mostly useful for adopting
firmware-allocated buffers via identity mappings. One common use-
case where this is required is if early firmware or bootloaders
have set up a bootsplash framebuffer that a display controller is
actively scanning out from during the operating system boot
process.
2. If an "iommu-addresses" property exists without a "reg" property,
the reserved-memory node describes an IOVA reservation. Such memory
regions are excluded from the IOVA space available to operating
system drivers and can be used for regions that must not be used to
map arbitrary buffers.
Each mapping or reservation is tied to a specific device via a phandle
to the device's device tree node. This allows a reserved-memory region
to be reused across multiple devices.
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20230120174251.4004100-3-thierry.reding@gmail.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.