[PATCH i-g-t 1/2] lib/i915: Add helper for copying engine maps from one context to another

[Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>]

From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>

We also need to support copying across file descriptors.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Sreedhar Telukuntla <sreedhar.telukuntla@xxxxxxxxx>
---
 lib/i915/gem_context.c | 30 ++++++++++++++++++++++++++++++
 lib/i915/gem_context.h |  2 ++
 2 files changed, 32 insertions(+)

diff --git a/lib/i915/gem_context.c b/lib/i915/gem_context.c
index 0b6a554dfe27..41957b66ca52 100644
--- a/lib/i915/gem_context.c
+++ b/lib/i915/gem_context.c
@@ -462,3 +462,33 @@ bool gem_context_has_engine(int fd, uint32_t ctx, uint64_t engine)
 
 	return __gem_execbuf(fd, &execbuf) == -ENOENT;
 }
+
+/**
+ * gem_context_copy_engines:
+ * @src_fd: open i915 drm file descriptor where @src context belongs to
+ * @src: source engine map context id
+ * @dst_fd: open i915 drm file descriptor where @dst context belongs to
+ * @dst: destination engine map context id
+ *
+ * Special purpose wrapper for copying engine map from one context to another.
+ *
+ * In can be called regardless of whether the kernel supports context engine
+ * maps and is a no-op if not supported.
+ */
+void
+gem_context_copy_engines(int src_fd, uint32_t src, int dst_fd, uint32_t dst)
+{
+	I915_DEFINE_CONTEXT_PARAM_ENGINES(engines, I915_EXEC_RING_MASK + 1);
+	struct drm_i915_gem_context_param param = {
+		.param = I915_CONTEXT_PARAM_ENGINES,
+		.ctx_id = src,
+		.size = sizeof(engines),
+		.value = to_user_pointer(&engines),
+	};
+
+	if (__gem_context_get_param(src_fd, &param) || !param.size)
+		return;
+
+	param.ctx_id = dst;
+	gem_context_set_param(dst_fd, &param);
+}
diff --git a/lib/i915/gem_context.h b/lib/i915/gem_context.h
index cf2ba33fee8f..15e5db281b79 100644
--- a/lib/i915/gem_context.h
+++ b/lib/i915/gem_context.h
@@ -42,6 +42,8 @@ uint32_t gem_context_clone(int i915,
 			   uint32_t src, unsigned int share,
 			   unsigned int flags);
 uint32_t gem_context_clone_with_engines(int i915, uint32_t src);
+void gem_context_copy_engines(int src_fd, uint32_t src,
+			      int dst_fd, uint32_t dst);
 
 uint32_t gem_queue_create(int i915);
 uint32_t gem_queue_clone_with_engines(int i915, uint32_t src);
-- 
2.20.1

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