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-rw-r--r--src/commonlib/include/commonlib/region.h7
-rw-r--r--src/commonlib/region.c12
2 files changed, 19 insertions, 0 deletions
diff --git a/src/commonlib/include/commonlib/region.h b/src/commonlib/include/commonlib/region.h
index cc4ee289d2..35d48ade85 100644
--- a/src/commonlib/include/commonlib/region.h
+++ b/src/commonlib/include/commonlib/region.h
@@ -121,6 +121,13 @@ static inline void *rdev_mmap_full(const struct region_device *rd)
return rdev_mmap(rd, 0, region_device_sz(rd));
}
+/*
+ * Compute relative offset of the child (c) w.r.t. the parent (p). Returns < 0
+ * when child is not within the parent's region.
+ */
+ssize_t rdev_relative_offset(const struct region_device *p,
+ const struct region_device *c);
+
struct mem_region_device {
char *base;
struct region_device rdev;
diff --git a/src/commonlib/region.c b/src/commonlib/region.c
index 8b0b0d9748..2cd273a883 100644
--- a/src/commonlib/region.c
+++ b/src/commonlib/region.c
@@ -48,6 +48,18 @@ static const struct region_device *rdev_root(const struct region_device *rdev)
return rdev->root;
}
+ssize_t rdev_relative_offset(const struct region_device *p,
+ const struct region_device *c)
+{
+ if (rdev_root(p) != rdev_root(c))
+ return -1;
+
+ if (!is_subregion(&p->region, &c->region))
+ return -1;
+
+ return region_device_offset(c) - region_device_offset(p);
+}
+
void *rdev_mmap(const struct region_device *rd, size_t offset, size_t size)
{
const struct region_device *rdev;