Segher Boessenkool wrote:

quoted

It's not what we do with flattened device trees blobs though.  In the
flattened tree we're not using a /chosen/stdout property, just the
linux,stdout-path one.

The question that remains is; should there be?  Should the dt blobs
use /chosen/stdout also?  (I'm not familiar enough with real OF to
know the answer.  I'm assuming that an instance value is not the same
as a phandle).

The difference between a phandle and an ihandle is similar to the 
difference between (the inode of) an executable files on disk and (the 
process id of) a running process.  A phandle refers to the static 
information that describes a device, while an ihandle refers to a 
particular (out of potentially several) active instantiation of the OFW 
driver for that devices.  An "instance value" is a data item that can 
have a different value for each of the running instances of a given 
driver.  In the analogy, an instance value is like a data segment variable.

Given an ihandle, you can get the corresponding phandle with 
ihandle>phandle.  You can't go from phandle to ihandle, because that 
direction is one-to-many.

Why you you ever need more than one running instance of a given driver?  
For leaf devices, it is pretty rare to have multiple instances.  
Multiple instances are more often used for intermediate nodes.  The same 
intermediate node - for example a usb node - is often the parent of 
several leaf nodes that are active simultaneously.  When you open a 
device, its device tree parents up to the root are implicitly opened.  
Each such instance can hold dynamic state on behalf of its children.

ihandles and phandles are not the same thing in OF.  Since in the
"flat world" we cannot have instances, we should use phandles instead
of ihandles for the things in /chosen.  I thought we agreed on that
already, perhaps I am wrong?


Segher

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