[PATCH pyphosphor 3/4] Added python to dts encoder

[Andrew Jeffery]

Hi Brad,

On Fri, 2016-04-15 at 07:50 -0500, OpenBMC Patches wrote:
> From: Brad Bishop <bradleyb at us.ibm.com>
> 
> This is a rudimentary python to device tree encoder.
> 
> It supports nested nodes and, cell, cell array,
> string, string array, and mixed array properties.
> At the moment there is no support for binary properties.

I think the patch should come with test cases exercising each of the
supported properties. For the tests themselves we can use dtc as an
oracle - throw the code at it and see if it compiles successfully (and
assume that the dts structure is what we wanted).

The tests would also serve as an example of how to invoke the root
dts_encode(), given it is self-recursive and seemingly has a bunch of
optional arguments to support that.

> ---
>  obmc/utils/dtree.py | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 63 insertions(+)
>  create mode 100644 obmc/utils/dtree.py
> 
> diff --git a/obmc/utils/dtree.py b/obmc/utils/dtree.py
> new file mode 100644
> index 0000000..ce349ee
> --- /dev/null
> +++ b/obmc/utils/dtree.py
> @@ -0,0 +1,63 @@
> +# Contributors Listed Below - COPYRIGHT 2016
> +# [+] International Business Machines Corp.
> +#
> +#
> +# Licensed under the Apache License, Version 2.0 (the "License");
> +# you may not use this file except in compliance with the License.
> +# You may obtain a copy of the License at
> +#
> +#     http://www.apache.org/licenses/LICENSE-2.0
> +#
> +# Unless required by applicable law or agreed to in writing, software
> +# distributed under the License is distributed on an "AS IS" BASIS,
> +# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
> +# implied. See the License for the specific language governing
> +# permissions and limitations under the License.
> +
> +
> +def dts_encode(obj, fd, **kw):
> +    ''' A rudimentary python to dts encoder.
> +    '''
> +    indent = kw.get('indent', 0)
> +    depth = kw.setdefault('depth', 0)
> +    tab = indent * depth * ' '
> +    kw['depth'] += 1
> +    newline = '\n' if indent else ' '
> +    context = kw.get('context')
> +
> +    if(isinstance(obj, dict)):
> +        nodes = []
> +        for k, v in obj.iteritems():
> +            if(isinstance(v, dict)):
> +                nodes.append((k, v))
> +                continue
> +            fd.write('%s%s = ' % (tab, k))
> +            dts_encode(v, fd, **kw)
> +            fd.write(";%s" % newline)
> +
> +        for k, v in nodes:
> +            fd.write('%s%s {%s' % (tab, k, newline))
> +            dts_encode(v, fd, **kw)
> +            fd.write('%s};%s' % (tab, newline))
> +
> +    if(isinstance(obj, int)):
> +        if context == 'int_list':
> +            fd.write("%d" % obj)
> +        else:
> +            fd.write("<%d>" % obj)
> +
> +    if(isinstance(obj, basestring)):
> +        fd.write("\"%s\"" % obj)
> +
> +    if(isinstance(obj, list)):
> +        ctx = 'int_list' if all((type(x) is int) for x in iter(obj)) else ''
> +        delim = ' ' if ctx is 'int_list' else ','
> +        closure = ('<', '>') if ctx is 'int_list' else ('', '')

We're branching twice on the same condition here. Perhaps:

    delim = ','
    closure = ('','')
    if ctx is 'int_list':
      delim = ' '
      closure = ('<', '>')

It's a little longer, but possibly a little clearer also?

> +
> +        fd.write(closure[0])
> +        for v in obj[:-1]:
> +            dts_encode(v, fd, context=ctx, **kw)
> +            fd.write(delim)
> +
> +        dts_encode(obj[-1], fd, context=ctx)
> +        fd.write(closure[1])

Cheers,

Andrew
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