fdt: Add simple alias support to fdt print command
PATCH 1/1 fdt: Add simple alias support to fdt print command
If the path we are trying to print doesn't exist see if it matches an aliases. We don't do anything fancy at this point, but just strip the leading '/' if it exists and see if we have an exact match to an alias.
In the future we could try and prefix matching so the alias could be used as a shorter path reference.
--- common/cmd_fdt.c | 20 +++++++++++++++++--- 1 files changed, 17 insertions(+), 3 deletions(-)
common/cmd_fdt.c +17 -3
@@ -678,9 +678,23 @@ static int fdt_print(const char *pathp, char *prop, int depth)/* * Not found or something else bad happened. */ -printf ("libfdt fdt_path_offset() returned %s\n" , -fdt_strerror (nodeoffset)); -return 1 ; + +/* see if we match an alias */ +int aliasoffset =fdt_path_offset (working_fdt,"/aliases" ); +if (aliasoffset >=0 ) { +const char *aliasp = pathp; +if (pathp[0 ] =='/' ) + aliasp++; + aliasp =fdt_getprop (working_fdt, + aliasoffset, aliasp,NULL ); + nodeoffset =fdt_path_offset (working_fdt, aliasp); + } + +if (nodeoffset <0 ) { +printf ("libfdt fdt_path_offset() returned %s\n" , +fdt_strerror (nodeoffset)); +return 1 ; + } }/* * The user passed in a property as well as node path.
Signature · 1 line
1.5.5.1
PATCH 1/1 fdt: Add simple alias support to fdt print command
Quoted 8 lines · Kumar Gala
If the path we are trying to print doesn't exist see if it matches an aliases. We don't do anything fancy at this point, but just strip the leading '/' if it exists and see if we have an exact match to an alias.
In the future we could try and prefix matching so the alias could be used as a shorter path reference.
Signed-off-by Kumar Gala <[email protected]>
Cool and useful too. Out of curiousity, does "real" Open Firmware do this sort of thing with aliases?
One reservation I have (which may disappear if the answer to the previous question is "yes"), it automatically and silently dereferences the /aliases/X node when asked to display /X or X (but only if /X doesn't exist in the dtb). This is not an obvious behavior since X isn't real.
Should we have a different display syntax to force the dereference of an alias X? Assuming "*" is a good choice, this would change the behavior
fdt print *ethernet0
to dereference /aliases/ethernet0 and print out
/soc8360 at e0000000/.../enet0 (or whatever).
Thanks,
gvb
PATCH 1/1 fdt: Add simple alias support to fdt print command
Quoted 11 lines · Jerry Van Baren
Quoted 9 lines · Kumar Gala
If the path we are trying to print doesn't exist see if it matches an aliases. We don't do anything fancy at this point, but just strip the
leading '/' if it exists and see if we have an exact match to an alias.
In the future we could try and prefix matching so the alias could be used
as a shorter path reference.Signed-off-by Kumar Gala <[email protected]>
Quoted 2 lines
Cool and useful too. Out of curiousity, does "real" Open Firmware do this sort of thing with aliases?
I'm pretty sure it the Apple OF implementation does. However I dont remember to what extent it does from my playing around with OF on Apple HW.
Quoted 5 lines
One reservation I have (which may disappear if the answer to the previous question is "yes"), it automatically and silently dereferences the /aliases/X node when asked to display /X or X (but only if /X doesn't exist in the dtb). This is not an obvious behavior since X isn't real.
we could print out something about using an alias so the user knows that its happening.
Quoted 6 lines
Should we have a different display syntax to force the dereference of an alias X? Assuming "*" is a good choice, this would change the behavior
fdt print *ethernet0
to dereference /aliases/ethernet0 and print out
/soc8360 at e0000000/.../enet0 (or whatever).
Lets says I have an alias for 'soc' to 'soc8360 at e000000'. I want to be able to in the future do print /soc/enet0 and have that work. Introducing some new syntax would make that difficult and more ugly.
- k
PATCH 1/1 fdt: Add simple alias support to fdt print command
Quoted 12 lines · Kumar Gala
Quoted 9 lines · Jerry Van Baren
Quoted 7 lines · Kumar Gala
If the path we are trying to print doesn't exist see if it matches an aliases. We don't do anything fancy at this point, but just strip the leading '/' if it exists and see if we have an exact match to an alias. In the future we could try and prefix matching so the alias could be used
as a shorter path reference.Signed-off-by Kumar Gala <[email protected]>
Quoted 5 lines
Quoted 2 lines
Cool and useful too. Out of curiousity, does "real" Open Firmware do this sort of thing with aliases?
I'm pretty sure it the Apple OF implementation does. However I dont remember to what extent it does from my playing around with OF on Apple HW.
Sounds like I'm going to have to preempt my kids on the olpc and see what OF does on it. :-)
Quoted 16 lines
Quoted 5 lines
One reservation I have (which may disappear if the answer to the previous question is "yes"), it automatically and silently dereferences the /aliases/X node when asked to display /X or X (but only if /X doesn't exist in the dtb). This is not an obvious behavior since X isn't real.
we could print out something about using an alias so the user knows that its happening.
Quoted 6 lines
Should we have a different display syntax to force the dereference of an alias X? Assuming "*" is a good choice, this would change the behavior
fdt print *ethernet0
to dereference /aliases/ethernet0 and print out
/soc8360 at e0000000/.../enet0 (or whatever).
Quoted 5 lines
Lets says I have an alias for 'soc' to 'soc8360 at e000000'. I want to be able to in the future do print /soc/enet0 and have that work. Introducing some new syntax would make that difficult and more ugly.
- k
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).
gvb
PATCH 1/1 fdt: Add simple alias support to fdt print command
Quoted 4 lines · Jerry Van Baren
Thinking out loud... we could define the syntax that a leading "*" indicates the first part of the path is a dereference of /aliases.
Quoted 11 lines
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
PATCH 1/1 fdt: Add simple alias support to fdt print command
Quoted 19 lines · Kumar Gala
Quoted 4 lines · Jerry Van Baren
Thinking out loud... we could define the syntax that a leading "*" indicates the first part of the path is a dereference of /aliases.
Quoted 11 lines
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).
Quoted 3 lines
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
PATCH 1/1 fdt: Add simple alias support to fdt print command
Quoted 30 lines · Jerry Van Baren
Quoted 19 lines · Kumar Gala
Quoted 4 lines · Jerry Van Baren
Thinking out loud... we could define the syntax that a leading "*" indicates the first part of the path is a dereference of /aliases.
Quoted 11 lines
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).Quoted 3 lines
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).
Quoted 7 lines
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>
No, I really don't think using this "dereference" character is a good idea. If you're going to expand aliases, you should do it as real OF does - see section 4.3 of IEEE1275. Essentially it's the *lack* of a leading '/' character that triggers alias expansion. So you could use e.g.
/soc8360 at e0000000/ethernet at e0000400 or soc/ethernet at e0000400
or
ethernet0
Quoted 11 lines
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.
----------------------------------------------------------------------
Quoted 9 lines
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.
I've observed a '*' in the device tree in the wild - some Apple tree, unfortunately I can't find it right at the moment. So I can't check if the '*' was in a node node, making it IEEE1275 illegal, or in a property name. I remember thinking it was illegal at the time, but I thought '*' was invalid in property names too, which seems to have been a misinterpretation.
Quoted 8 lines
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...
If you're interepreting them in one place, you should probably interpret them everywhwere and have a single "resolve pathname" function. In fact, I should quite possibly put such a function into libfdt.
Signature · 4 lines
David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
PATCH 1/1 fdt: Add simple alias support to fdt print command
Quoted 1 line · David Gibson
On Sat, Aug 02, 2008 at 08:51:54PM -0400, Jerry Van Baren wrote:
[snip]
Quoted 13 lines
Quoted 7 lines
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>No, I really don't think using this "dereference" character is a good idea. If you're going to expand aliases, you should do it as real OF does - see section 4.3 of IEEE1275. Essentially it's the *lack* of a leading '/' character that triggers alias expansion. So you could use e.g.
Quoted 5 lines
/soc8360 at e0000000/ethernet at e0000400 or soc/ethernet at e0000400or
ethernet0
Ahh, I didn't read far enough. The algorithm in section 4.3 is much better thought out than either of our proposals.
[snip]
Quoted 3 lines
If you're interepreting them in one place, you should probably interpret them everywhwere and have a single "resolve pathname" function.
Yes.
Quoted 1 line
In fact, I should quite possibly put such a function into libfdt.
That would be very useful. :-)
Thanks,
gvb