HACKING revision 245803
1245803Stheraven$FreeBSD: head/usr.bin/dtc/HACKING 245803 2013-01-22 17:49:51Z 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 24245803StheravenThis project currently aims to compile with g++ 4.2.1 and so doesn't make any 25245803Stheravenuse of C++11 features. It would be a good idea to relax this restriction once 26245803Stheravenclang is the default compiler for ARM, MIPS and PowerPC. 27245803Stheraven 28245803StheravenThis code makes use of a lot of iterator loops, which would be cleaner using 29245803Stheraventhe new syntax in C++11. It also explicitly deletes a lot of objects held in 30245803Stheravencollections in destructors that have these collections as their members. This 31245803Stheravencould be simplified by using `shared_ptr`. 32245803Stheraven 33245803StheravenThe code does make use of `static_assert()`, but uses a macro in utility.hh to 34245803Stheravenremove these if they are not supported. The FreeBSD standard headers also 35245803Stheravendefine a compatibility macro the implements static asserts in terms of an array 36245803Stheravenwith 1 element on success and -1 elements on failure. 37245803Stheraven 38245803StheravenAdding New Checks 39245803Stheraven----------------- 40245803Stheraven 41245803StheravenCurrently, the biggest weakness of this version of the tool is that it lacks 42245803Stheravenmost of the semantic checkers that can be implemented by simply reading the 43245803StheravenePAPR spec. The `checker` class provides a simple superclass for implementing 44245803Stheraventhese quite easily. There are also helper methods on `device_tree` for finding 45245803Stheravenspecific nodes, for checks that require some understanding of the structure of 46245803Stheraventhe tree. 47245803Stheraven 48245803StheravenWe should probably add a parent pointer to the `node` class for easily walking 49245803Stheravenup the tree. 50245803Stheraven 51245803StheravenAdding Direct C Output 52245803Stheraven---------------------- 53245803Stheraven 54245803StheravenThe FreeBSD build system currently uses dtc to generate a blob and then 55245803Stheravenconverts this to C source code. A new `output_writer` subclass could easily 56245803Stheravengenerate the C directly. 57245803Stheraven 58245803StheravenParser Improvements 59245803Stheraven------------------- 60245803Stheraven 61245803StheravenThere are a few FIXME lines in the parser for some corner cases that are not 62245803Stheravencurrently used by FreeBSD. These are mainly related to labels in the middle of 63245803Stheravenvalues. These can be fixed by creating a new `property_value` with the 64245803Stheravenspecified label, starting at the location of the label. Don't forget to remove 65245803Stheraventhe associated comments from the BUGS section of the man page if you fix this. 66