Patch for Cross-Reference Phandles

[Ian Lepore]

On Sat, 2013-09-14 at 09:06 -0500, Nathan Whitehorn wrote:
> On 09/14/13 08:31, Marius Strobl wrote:
> > On Thu, Sep 12, 2013 at 10:07:18AM -0500, Nathan Whitehorn wrote:
> >> On 09/08/13 13:54, Nathan Whitehorn wrote:
> >>> Open Firmware has three namespaces for handles:
> >>> 1. Instance handles, for open devices
> >>> 2. Package handles for the client interface
> >>> 3. Package handles for device tree cross references
> >>>
> >>> On Powermac hardware, we assume that (2) and (3) are identical and
> >>> call both phandles. On embedded FDT systems, you can't open devices
> >>> and so we abuse ihandle_t for (3). IBM pSeries hardware, however, has
> >>> all three things. With that in mind, I'd like to start separating
> >>> them. The patch at
> >>> http://people.freebsd.org/~nwhitehorn/xref_phandle.diff adds a new
> >>> function (OF_child_xref_phandle) that takes a phandle of type (3) and
> >>> turns into one of type (2) by searching for entries named "phandle",
> >>> "ibm,phandle", or "linux,phandle" in the tree. This should work for
> >>> FDT as well, but is not connected in the patch to anything actually
> >>> FDT related.
> >>>
> >>> Comments would be appreciated. I'd like to get to get this as in as
> >>> soon as possible (given the HEAD freeze) otherwise.
> >>> -Nathan
> >> Since I haven't heard anything, it shouldn't affect any existing
> >> platforms or code, and it would be nice to have this interface available
> >> in the 10.x series, I plan to ask re@ for commit approval tomorrow.
> >> Please let me know if there are any objections.
> > Technically that patch is fine. It would be nice if you could fix the
> > style bugs before committing, though. In OF_child_xref_phandle(), the
> > variables should go above the comment and you don't need to initialize
> > the static global one in ofw_pcibus.c to zero explicitly. If you do
> > nevertheless, spaces should go before and after the '='.
> >
> 
> Thanks! I think the explicit zero initialization adds some clarity for 
> people reading the code, so I'd like to keep it. The rest of the changes 
> have been made.
> -Nathan

The explicit zero init also makes it 4 bytes harder to fit the kernel
into a small flash on embedded systems.  We should be eliminating
zero-inits that move items from bss to data, not adding new ones.

-- Ian