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freebsd-skq/usr.bin/dtc/HACKING

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Import new (BSDL) device tree compiler. Now built by default, so that it can't be used on the host system (and not installed on the device, if required). The GPL'd one is still available if there are any devices that need it (make universe passes with it, including kernels that use fdt, but there may be some out-of-tree ones). WITH_GPL_DTC can be used to select the old one, for now. Probably won't be MFC'd, but we'll remove the GPL'd version in head after the new one has had a lot more testing and ship it in 10.0.
2013-01-22 17:49:51 +00:00
$FreeBSD$
Notes for people hacking on dtc
===============================
This file contains some notes for people wishing to hack on dtc.
Upstreaming
-----------
dtc(1): Update to 0892ec7; HACKING and implicit header fixes Fixes courtesy of arichardson and jmg: - HACKING was pointing to the wrong place - Added headers were being relied on implicitly, but libstdc++ did not comply with the unspoken wishes of dtc. MFC after: 1 week
2018-08-23 02:26:40 +00:00
This code is developed in the git repository:
Import new (BSDL) device tree compiler. Now built by default, so that it can't be used on the host system (and not installed on the device, if required). The GPL'd one is still available if there are any devices that need it (make universe passes with it, including kernels that use fdt, but there may be some out-of-tree ones). WITH_GPL_DTC can be used to select the old one, for now. Probably won't be MFC'd, but we'll remove the GPL'd version in head after the new one has had a lot more testing and ship it in 10.0.
2013-01-22 17:49:51 +00:00
dtc(1): Update to 0892ec7; HACKING and implicit header fixes Fixes courtesy of arichardson and jmg: - HACKING was pointing to the wrong place - Added headers were being relied on implicitly, but libstdc++ did not comply with the unspoken wishes of dtc. MFC after: 1 week
2018-08-23 02:26:40 +00:00
https://github.com/davidchisnall/dtc
Import new (BSDL) device tree compiler. Now built by default, so that it can't be used on the host system (and not installed on the device, if required). The GPL'd one is still available if there are any devices that need it (make universe passes with it, including kernels that use fdt, but there may be some out-of-tree ones). WITH_GPL_DTC can be used to select the old one, for now. Probably won't be MFC'd, but we'll remove the GPL'd version in head after the new one has had a lot more testing and ship it in 10.0.
2013-01-22 17:49:51 +00:00
If you got the source from anywhere else and wish to make changes, please
ensure that you are working against the latest version, or you may end up
fixing bugs that are already fixed upstream. Although the license makes no
requirement that you share any improvements that you make, patches are very
welcome.
C++11
-----
Update some obsolete information in the HACKING document. Reported by: bapt
2015-10-26 11:02:57 +00:00
This project uses C++11, as the goal for FreeBSD 11 is to require C/C++11 as a
minimum, either from clang or an external toolchain. In particular, it uses
`std::unique_ptr` extensively for memory management within the tree. Unique
pointers are also used in several other places to track ownership.
Most iterator loops use the new loop syntax and the `auto` type for type
deduction. Range-based `for` loops generally improve the readability of the
code, though `auto` should only be used in places where the type can be deduced
as easily by the reader as by the compiler.
The code also makes use of `static_assert()` to track compile-time invariants.
Import new (BSDL) device tree compiler. Now built by default, so that it can't be used on the host system (and not installed on the device, if required). The GPL'd one is still available if there are any devices that need it (make universe passes with it, including kernels that use fdt, but there may be some out-of-tree ones). WITH_GPL_DTC can be used to select the old one, for now. Probably won't be MFC'd, but we'll remove the GPL'd version in head after the new one has had a lot more testing and ship it in 10.0.
2013-01-22 17:49:51 +00:00
Adding New Checks
-----------------
Currently, the biggest weakness of this version of the tool is that it lacks
most of the semantic checkers that can be implemented by simply reading the
ePAPR spec. The `checker` class provides a simple superclass for implementing
these quite easily. There are also helper methods on `device_tree` for finding
specific nodes, for checks that require some understanding of the structure of
the tree.
We should probably add a parent pointer to the `node` class for easily walking
up the tree.
Adding Direct C Output
----------------------
The FreeBSD build system currently uses dtc to generate a blob and then
converts this to C source code. A new `output_writer` subclass could easily
generate the C directly.
Parser Improvements
-------------------
There are a few FIXME lines in the parser for some corner cases that are not
currently used by FreeBSD. These are mainly related to labels in the middle of
values. These can be fixed by creating a new `property_value` with the
specified label, starting at the location of the label. Don't forget to remove
the associated comments from the BUGS section of the man page if you fix this.
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