Currently, the Linux kernel, libfdt and dtc, when using flattened
device trees encode a node's phandle into a property named
"linux,phandle". The ePAPR specification, however - aiming as it is
to not be a Linux specific spec - requires that phandles be encoded in
a property named simply "phandle".
This patch adds support for this newer approach to dtc and libfdt.
Specifically:
- fdt_get_phandle() will now return the correct phandle if it
is supplied in either of these properties
- fdt_node_offset_by_phandle() will correctly find a node with
the given phandle encoded in either property.
- By default, when auto-generating phandles, dtc will encode
it into both properties for maximum compatibility. A new -H
option allows either only old-style or only new-style
properties to be generated.
- If phandle properties are explicitly supplied in the dts
file, dtc will not auto-generate ones in the alternate format.
- If both properties are supplied, dtc will check that they
have the same value.
- Some existing testcases are updated to use a mix of old and
new-style phandles, partially testing the changes.
- A new phandle_format test further tests the libfdt support,
and the -H option.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Currently, dtc will generate phandles for nodes which are referenced
elsewhere in the tree. phandles can also be explicitly assigned by
defining the linux,phandle property. However, there is no way,
currently to tell dtc to generate a phandle for a node if it is not
referenced elsewhere. This is inconvenient when it's expected that
later processing on the flat tree might add nodes which _will_
the node in question.
One way one might attempt to do this is with the construct:
mynode: mynode {
linux,phandle = <&mynode>;
/* ... */
};
Though it's a trifle odd, there's really only one sensible meaning
which can be assigned to this construct: allocate a unique phandle to
"mynode" and put that in its linux,phandle property (as always).
Currently, however, dtc will choke on this self-reference. This patch
corrects this, making the construct above give the expected results.
It also ensures a more meaningful error message is given if you
attempt to process the nonsensical construct:
mynode: mynode {
linux,phandle = <&someothernode>;
/* ... */
};
The 'references' testcase is extended to cover this case, as well.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
The recent change to the lexer to only recognize property and node
names in the appropriate context removed a number of lexical warts in
our language that would have gotten ugly as we add expression support
and so forth.
But there's one nasty one remaining: references can contain a full
path, including the various problematic node name characters (',', '+'
and '-', for example). This would cause trouble with expressions, and
it also causes trouble with the patch I'm working on to allow
expanding references to paths rather than phandles. This patch
therefore reworks the lexer to mitigate these problems.
- References to labels cause no problems. These are now
recognized separately from references to full paths. No syntax change
here.
- References to full paths, including problematic characters
are allowed by "quoting" the path with braces
e.g. &{/pci@10000/somedevice@3,8000}. The braces protect any internal
problematic characters from being confused with operators or whatever.
- For compatibility with existing dts files, in v0 dts files
we allow bare references to paths as before &/foo/bar/whatever - but
*only* if the path contains no troublesome characters. Specifically
only [a-zA-Z0-9_@/] are allowed.
This is an incompatible change to the dts-v1 format, but since AFAIK
no-one has yet switched to dts-v1 files, I think we can get away with
it. Better to make the transition when people to convert to v1, and
get rid of the problematic old syntax.
Strictly speaking, it's also an incompatible change to the v0 format,
since some path references that were allowed before are no longer
allowed. I suspect no-one has been using the no-longer-supported
forms (certainly none of the kernel dts files will cause trouble).
We might need to think about this harder, though.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
David Gibson