David Gibson wrote:
On Fri, Mar 02, 2007 at 12:25:17AM -0500, Jerry Van Baren wrote:
David Gibson wrote:
On Thu, Mar 01, 2007 at 11:08:38PM -0500, Jerry Van Baren wrote:
[snip]
to give me a pointer to the node name for node tags and property name for property tags. Now that I have it working, it would be trivial to change the calls to _fdt_next_tag() to instead call fdt_next_tag() passing NULL for the new fourth parameter **namep. ;-)
The reason I need it, I'm printing an unknown tree by stepping through the tree discovering the node and property names. I need to have fdt_next_tag() return the *name* of the node/property as well as the tag so that I can print and indent for nodes or look up the property value and print the name=value combination.
Hrm. And it returns NULL for tags without a name?
I was unable to generate a tag without a name using dtc (other than the root node). It should/would return null, which would be a problem. :-/
I was thinking more of tag types which don't have a name, to wit, FDT_END_NODE and FDT_NOP.
That might be a useful extension for the next_tag function. The one thing I'm concerned about is who's responsible for verifying the name pointer. I'm trying to keep libfdt robust enough that evern if presented with a badly corrupt blob it will fail relatively gracefully. Ideally, no matter what it's presented with, it will always return at worst FDT_ERR_BADSTRUCTURE rather than crashing and will under no circumstances access memory outside the given blob size.
[snip]
Oh gaak! What I hear you saying... if you have node a with subnode b and property b, subnode b has a property c: /a => node /a/b => node /a/b => property (inside node a) /a/b/c => property (inside node b)
Well, yes. Except that in OF and derived terminology, properties are *never* referred to by path in this way. It's always: "property 'fred' of node /foo/bar/baz"
I'm coming from a human interface syntax point of view and assumed that the human interface is paths like linux where the last item is a directory or file with the computer guessing what you really meant (which _isn't_ ambiguous in file/dir paths). Is there a better syntax for distinguishing between node paths and properties?
You assumed incorrectly. Well, unless you count /proc/device-tree as a human interface to the device tree, which isn't entirely unreasonable. OF certainly doesn't use that approach, it uses state instead, first "dev /foo/bar/baz" then ".properties" or "setprop ....".
OF is a programming language that has some crude elements of interaction (wouldn't that be "/foo/bar/baz" dev in Forthspeak? ;-). Making user interface commands have state, where you do "fdt dev /foo/bar/baz" (remembering the offset of the node) and then "fdt .properties" implicitly working on /foo/bar/baz is ugly ugly ugly.
We need a usable human interface syntax, replacing the last "/" with some other character that is not a legal character for a name and thus won't cause confusion. I am not familiar enough with OF to know if there is a unique character that can be used for the node path vs. property separator. If someone has a good one, hollar, otherwise I'll do some more research when I have time.
Lacking a good property separator character, I will be sticking with the convention that the stuff after the last "/" is a node unless that assumption is wrong, in which case it is a property.
Best regards, gvb