On 2008-11-07 at 02:31:40, David Gibson wrote:

On Thu, Nov 06, 2008 at 06:55:44PM +1100, Michael Ellerman wrote:

quoted

This commit adds an output format, which produces python
code. When run, the python produces a data structure that
can then be inspected in order to do various things.

...

quoted

I'm not sure if this is generally useful (or sane) but it was for me 
so
I thought I'd post it.

Hrm, well the idea of langauge source output seems reasonable.  But
the actual data structure emitted, and the method of construction in
Python both seem a bit odd to me.

quoted

I have a dts that I want to use to configure a simulator, and this
seemed like the nicest way to get there. dtc spits out the pythonised
device tree, and then I have a 10 line python script that does the
configuring.

[snip]

These branches also result in the value having different Python types
depending on the context.  That's not necessarily a bad thing, but
since which Python type is chosen depends on a heuristic only, it
certainly needs some care.  You certainly need to be certain that you
can always deduce the exact, byte-for-byte correct version of the
property value from whatever you put into the Python data structure.

quoted

 +
 +out:
 +     fprintf(f, "    n.properties.append(p)\n");

So, emitting Python procedural code to build up the data structure,
rather than a great big Python literal that the Python parser will
just turn into the right thing seems a bit of a roundabout way of
doing this.

I would think so too.   I haven't looked at the output, only at Davids 
comments.  If the data structure is ambiguous, then I do think more 
thought is needed.

Have you considered just parsing the flat tree binary?   Either 
creating a python binding to libfdt or even just parsing the dtb 
directly?

I have written perl code to parse a dtb and query it for nodes and 
properties, it wasn't too bad.  I need to look at a bug report by 
another user and comment it, then I should seek the okays post it.  It 
is currently read-only and iterative callback based (like the kernels 
early-scan-flat-tree stuff), but I have planned creating a tree for 
querying, editing, and re-flattening.  Perl strings are counted length 
binary blobs, so property contents are interpreted with pack and 
unpack.  The library has been used to search a dtb to build a list of 
cpu instances and memory blocks, and it has been used to query the 
properties of a known node in the tree.

milton