[PATCH v2] drm/ttm: add generic drvparam[] alias for ttm_place::fpfn/lpfn

[Arunpravin Paneer Selvam]

The fpfn/lpfn fields in struct ttm_place are named after page frame
numbers, but they are really just placement parameters interpreted by
the backend resource manager. Wrap them in a union with a generic
drvparam[2] array so backends can access the same storage without the
PFN-specific naming.

drvparam[0]/drvparam[1] alias fpfn/lpfn, so existing users and the
VRAM range manager are unchanged. This decouples the API from
PFN/range-specific semantics so that these fields can be used more
flexibly in the future (e.g. mask-based or segment-aware placement
constraints). No functional change.

v2: Use a union exposing a generic drvparam[2] array instead of
    renaming fpfn/lpfn to param1/param2, keeping existing users
    unchanged (Tvrtko Ursulin)

Suggested-by: Christian König <christian.koenig@xxxxxxx>
Assisted-by: Claude:claude-opus-4-8
Cc: Christian König <christian.koenig@xxxxxxx>
Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Cc: Matthew Auld <matthew.auld@xxxxxxxxx>
Cc: Matthew Brost <matthew.brost@xxxxxxxxx>
Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@xxxxxxx>
---
 include/drm/ttm/ttm_placement.h | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/drm/ttm/ttm_placement.h b/include/drm/ttm/ttm_placement.h
index ab2639e42c54..7db2073f3236 100644
--- a/include/drm/ttm/ttm_placement.h
+++ b/include/drm/ttm/ttm_placement.h
@@ -75,14 +75,22 @@
  *
  * @fpfn:	first valid page frame number to put the object
  * @lpfn:	last valid page frame number to put the object
+ * @drvparam:	generic driver/backend placement parameters; the
+ *		interpretation is defined by the backend resource manager.
+ *		drvparam[0] and drvparam[1] alias @fpfn and @lpfn.
  * @mem_type:	One of TTM_PL_* where the resource should be allocated from.
  * @flags:	memory domain and caching flags for the object
  *
  * Structure indicating a possible place to put an object.
  */
 struct ttm_place {
-	uint64_t	fpfn;
-	uint64_t	lpfn;
+	union {
+		struct {
+			uint64_t	fpfn;
+			uint64_t	lpfn;
+		};
+		uint64_t	drvparam[2];
+	};
 	uint32_t	mem_type;
 	uint32_t	flags;
 };

base-commit: cdeb2ccd993ed8647adbbda2c3b103aa717fd6f7
-- 
2.34.1