On 11/20/2017 10:56 AM, Sudeep Holla wrote:

(trimming)

quoted

   *	case there's no explicit cache node or the cache node itself in the
   *	device tree
+ * @firmware_node: Shared with of_node. When not using DT, this may contain
+ *	pointers to other firmware based values. Particularly ACPI/PPTT
+ *	unique values.
   * @disable_sysfs: indicates whether this node is visible to the user via
   *	sysfs or not
   * @priv: pointer to any private data structure specific to particular

@@ -64,8 +67,10 @@ struct cacheinfo {
  #define CACHE_ALLOCATE_POLICY_MASK	\
  	(CACHE_READ_ALLOCATE | CACHE_WRITE_ALLOCATE)
  #define CACHE_ID		BIT(4)
-
-	struct device_node *of_node;
+	union {
+		struct device_node *of_node;
+		void *firmware_node;
+	};

I would prefer
	struct device_node *of_node;
changed to
	struct fwnode_handle *fwnode;

You can then have
	struct pptt_fwnode {
		<.....>
		/*below fwnode  allocated using acpi_alloc_fwnode_static */
		struct fwnode_handle *fwnode;
	};

This gives a good starting point to abstract DT and ACPI.

If not now, we can later implement fwnode.ops=pptt_cache_ops and then
use get property for both DT and ACPI.

I'm obviously confused why this keeps coming up. On the surface it 
sounds like a good idea. But then, given that I've actually implemented 
a portion of it, what becomes clear is that the PPTT isn't a good match. 
Converting the OF routines to use the fwnode is fairly straightforward, 
but that doesn't help the ACPI situation other than to create a lot of 
misleading code (and the possibility of creating nonstandard DSDT 
entries). The fact that this hasn't been done for other tables 
MADT/SLIT/SRAT/etc makes me wonder why we should do it for the PPTT?

Particularly, when one considers fwnode is more a DSDT<->DT abstraction 
and thus has a lot of API surface that simply doesn't make any sense 
given the PPTT binary tree structure. Given that most of the fwnode 
routines are translating string properties (for example 
fwnode_property_read_string()) it might be possible to build a 
translator of some form which takes DT style properties and attempts to 
map them to the ACPI PPTT tree. What this adds I can't fathom, beyond 
the fact that suddenly the fwnode interface is a partial/brittle 
implementation where a large subset of the fwnode_operations will tend 
to be degenerate cases. The result likely will be a poorly implemented 
translator which breaks or is meaningless over a large part of the 
fwnode API surface.