[U-Boot-Users] [PATCH] fdt: Add simple alias support to fdt print command

[Jerry Van Baren]

Kumar Gala wrote:
> 
> On Jul 9, 2008, at 12:02 PM, Jerry Van Baren wrote:
> 
>>
>> Thinking out loud... we could define the syntax that a leading "*" 
>> indicates the first part of the path is a dereference of /aliases.
>>
>> Assuming
>>  /aliases/soc = /soc8360 at e000000
>>  /aliases/ethernet0 = /soc8360 at e0000000/.../enet0
>> then
>>  print *soc/enet0
>> and
>>  print *ethernet0
>> would both work and print the right thing.  You *would* have to know 
>> that the first element of the path is an /aliases dereference.  Your 
>> original patch did not require that piece of knowledge (but silently 
>> and automagically, which makes me nervous).
> 
> did we come to resolution on this?  I'd like to see this in 1.3.5.
> 
> - k

Hi Kumar,

I think we have basic resolution - I would like to see it in 1.3.5 too. 
  I haven't pushed on this, waiting for 1.3.5 window to open (or some 
free time, whichever comes last).

I've CC:ed David Gibson in case he has some advice - the concept is to 
indicate a dereference of /aliases nodes so that us lazy engineers don't 
have to cut'n'paste the whole long path from the alias.  Kumar 
originally proposed to do it automagically and I countered proposing 
using "*" to indicate the next path name should be looked up in /aliases 
and the result used instead (i.e. dereferenced).  Discussion thread:
<http://thread.gmane.org/gmane.comp.boot-loaders.u-boot/43575/focus=44941>

Looking at the ieee1275 doc
<http://playground.sun.com/pub/1275/coredoc/1275-1994/1275.ps.gz>
it looks like "*" will work for a dereference delimiter as it is not 
listed as one of the permitted punctuation characters in a node name. 
Quoting 3.2.1.1 Node names:
----------------------------------------------------------------------
The driver name field is a sequence of between one and 31 letters, 
digits, and punctuation characters from the set ", . _ + - ". Uppercase 
and lowercase characters are distinct.
----------------------------------------------------------------------

We do have a problem with property names, where "*" _is_ a legal name 
component.  Quoting 3.2.2.1.1 Property names:
----------------------------------------------------------------------
The property name is a human-readable text string consisting of one to 
thirty-one printable characters. Property names shall not contain 
uppercase characters or the characters "/", "\", ":", "[", "]" and "@".
----------------------------------------------------------------------
Note that "*" is not proscribed, making it a legal character in a 
property name.

Having noted that, I'm willing to take the risk and use "*" for the 
"alias dereference" separator.

Looking back at the original patch, Kumar's original patch only did the 
/aliases dereference for the "fdt print" command.  I'm thinking more 
general purpose: being able to dereference /aliases in all "fdt" 
commands.  This seems helpful for the "fdt set" command, for instance. 
Whether this is reasonable to implement remains to be seen...

Best regards,
gvb