1245803Stheraven$FreeBSD: releng/11.0/usr.bin/dtc/HACKING 289996 2015-10-26 11:02:57Z theraven $ 2245803Stheraven 3245803StheravenNotes for people hacking on dtc 4245803Stheraven=============================== 5245803Stheraven 6245803StheravenThis file contains some notes for people wishing to hack on dtc. 7245803Stheraven 8245803StheravenUpstreaming 9245803Stheraven----------- 10245803Stheraven 11245803StheravenThis code is developed in the FreeBSD svn repository: 12245803Stheraven 13245803Stheravenhttps://svn.freebsd.org/base/head/usr.bin/dtc 14245803Stheraven 15245803StheravenIf you got the source from anywhere else and wish to make changes, please 16245803Stheravenensure that you are working against the latest version, or you may end up 17245803Stheravenfixing bugs that are already fixed upstream. Although the license makes no 18245803Stheravenrequirement that you share any improvements that you make, patches are very 19245803Stheravenwelcome. 20245803Stheraven 21245803StheravenC++11 22245803Stheraven----- 23245803Stheraven 24289996StheravenThis project uses C++11, as the goal for FreeBSD 11 is to require C/C++11 as a 25289996Stheravenminimum, either from clang or an external toolchain. In particular, it uses 26289996Stheraven`std::unique_ptr` extensively for memory management within the tree. Unique 27289996Stheravenpointers are also used in several other places to track ownership. 28245803Stheraven 29289996StheravenMost iterator loops use the new loop syntax and the `auto` type for type 30289996Stheravendeduction. Range-based `for` loops generally improve the readability of the 31289996Stheravencode, though `auto` should only be used in places where the type can be deduced 32289996Stheravenas easily by the reader as by the compiler. 33245803Stheraven 34289996StheravenThe code also makes use of `static_assert()` to track compile-time invariants. 35245803Stheraven 36245803StheravenAdding New Checks 37245803Stheraven----------------- 38245803Stheraven 39245803StheravenCurrently, the biggest weakness of this version of the tool is that it lacks 40245803Stheravenmost of the semantic checkers that can be implemented by simply reading the 41245803StheravenePAPR spec. The `checker` class provides a simple superclass for implementing 42245803Stheraventhese quite easily. There are also helper methods on `device_tree` for finding 43245803Stheravenspecific nodes, for checks that require some understanding of the structure of 44245803Stheraventhe tree. 45245803Stheraven 46245803StheravenWe should probably add a parent pointer to the `node` class for easily walking 47245803Stheravenup the tree. 48245803Stheraven 49245803StheravenAdding Direct C Output 50245803Stheraven---------------------- 51245803Stheraven 52245803StheravenThe FreeBSD build system currently uses dtc to generate a blob and then 53245803Stheravenconverts this to C source code. A new `output_writer` subclass could easily 54245803Stheravengenerate the C directly. 55245803Stheraven 56245803StheravenParser Improvements 57245803Stheraven------------------- 58245803Stheraven 59245803StheravenThere are a few FIXME lines in the parser for some corner cases that are not 60245803Stheravencurrently used by FreeBSD. These are mainly related to labels in the middle of 61245803Stheravenvalues. These can be fixed by creating a new `property_value` with the 62245803Stheravenspecified label, starting at the location of the label. Don't forget to remove 63245803Stheraventhe associated comments from the BUGS section of the man page if you fix this. 64