Re: RFC: Mega rename of device tree routines from of_*() to dt_*()

From: Mitch Bradley
Date: Thu Nov 25 2010 - 23:49:50 EST

On 11/25/2010 5:15 PM, Michael Ellerman wrote:
On Thu, 2010-11-25 at 09:17 -0700, Grant Likely wrote:
On Thu, Nov 25, 2010 at 6:34 AM, Michael Ellerman
<michael@xxxxxxxxxxxxxx> wrote:
On Thu, 2010-11-25 at 01:03 +1100, Michael Ellerman wrote:
Hi all,

There were some murmurings on IRC last week about renaming the of_*()
routines.
...
The thinking is that on many platforms that use the of_() routines
OpenFirmware is not involved at all, this is true even on many powerpc
platforms. Also for folks who don't know the OpenFirmware connection
it reads as "of", as in "a can of worms".
...
So I'm hoping people with either say "YES this is a great idea", or "NO
this is stupid".

I'm still hoping, but so far it seems most people have got better things
to do, and of those that do have an opinion the balance is slightly
positive.

I assume you'll be also publishing the script that you use for
generating the massive patch. I expect that there will be a few
iterations of running the rename script to convert over all the
stragglers.

Yep sure, I'll just make it less crap first.

It should also be negotiated with Linus about when this
patch should get applied. I do NOT want to cause massive merge pain
during the merge window.

Obviously.

Andrew/Linus: Before Michael proceeds too far with this rename, are
you okay with a mass rename of the device tree functions from of_* to
dt_*? Nobody likes the ambiguous 'of_' prefix ("of? of what?"), but
to fix it means large cross-tree patches and potential merge
conflicts.

It'd also be good to hear from DaveM, sparc is the platform with the
strongest link to real OF AFAIK, so the of_() names make more sense
there.


One Laptop Per Child ships real Open Firmware on its x86 Linux systems, of which approximately 2 million have been shipped or ordered. An ARM version, also with OFW, is in the works. From the standpoint of "number of units in the field actually running Linux", I expect that compares favorably with SPARC.

That said, I don't particularly like the abbreviation "of" either; I abbreviate Open Firmware as "OFW".

I don't mind using "dt_" to apply to device tree things; I think it's clearer than "of_". Ideally, it would be nice to acknowledge the historical connection in some way, but confusing nomenclature probably is not the way to go about it.




So here's a first cut of a patch to add the new names. I've not touched
of_platform because that is supposed to go away. That will lead to some
odd looking code in the interim, but I think is the right approach.

I would split it up into separate dt*.h files, one for each of*.h file
so that the #include lines can be changed in the C code at the same
time. Each dt*.h file would include it's of*.h counterpart. Then
after the code is renamed, and a release or two has passed to catch
the majority of users, the old definitions can be moved into the dt*.h
files.

Yep that sounds like a plan. I did it as a single header for starters so
I could autogenerate the rename script easily.

However, it may be better to move and rename the definitions
immediately, and leave "#define of_* dt_*" macros in the old of*.h
files which can be removed with a simple patch after all the users are
converted. That would have a smaller impact in the cleanup stage.

True, though a bigger impact to start with. I did that originally but
decided it might be better to start with the minimal patch to add the
new names. That way Linus might accept it this release, meaning we'd
have the new names in place for code in -next.

Most of these are straight renames, but some have changed more
substantially. The routines for the flat tree have all become fdt_foo().
I'd be inclined to drop "early_init" from them too, because they're
basically all about early init, but Grant said he'd prefer not to I
think. I've also renamed the flat tree tag constants to match libfdt.

It is all about early init now in Linus' tree, but Stephen
Neuendorffer has patches that use the fdt code at driver probe time
for parsing device tree fragments that describe an FPGA add-in board.

OK fair enough.

I've left for_each_child_of_node(), because I read it as "of", but maybe
it's "OF"?

hahaha! I never considered that it might be OF, but now I probably
won't be able to help but read it that way! I like Geert's suggestion
of dt_for_each_child_node

OK, I like it the way it is, but if the consensus is to change it then
we can. There's a bunch actually:

for_each_node_by_name(dn, name) \
for_each_node_by_type(dn, type) \
for_each_compatible_node(dn, type, compatible) \
for_each_matching_node(dn, matches) \
for_each_child_of_node(parent, child) \
for_each_node_with_property(dn, prop_name) \

So either dt_for_each_blah(), or for_each_dt_node_blah() ?

/* include/linux/device.h */
#define dt_match_table of_match_table
#define dt_node of_node

This could be very messy. I've nervous about using #define to rename
structure members. You'll need to check that any structure members
that use the same name as a global symbol are handled appropriately.

I'm not sure what you mean about global symbols.

I think it's fairly safe, in that direction, ie. defining the dt_*
names. Neither of those strings appears anywhere in the tree at the
moment (as a token).

cheers




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