[PATCH 1/7] mm: rust: add pgprot_noncached helper

[Deborah Brouwer]

From: Daniel Almeida <daniel.almeida@xxxxxxxxxxxxx>

Expose pgprot_noncached() to Rust code through a small helper wrapper.

Rust drivers that insert raw PFN mappings into userspace MMIO VMAs need
to derive an appropriate non-cached pgprot before calling helpers such
as vmf_insert_pfn_prot(). pgprot_noncached() is currently inaccessible
from Rust because it is provided through C helpers/macros rather than a
normal exported symbol.

Add a Rust helper wrapper so Rust MMIO mmap paths can construct
non-cached page protections for device mappings.

Signed-off-by: Daniel Almeida <daniel.almeida@xxxxxxxxxxxxx>
Signed-off-by: Deborah Brouwer <deborah.brouwer@xxxxxxxxxxxxx>
---
 rust/helpers/mm.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/rust/helpers/mm.c b/rust/helpers/mm.c
index b5540997bd20..22194d3196d2 100644
--- a/rust/helpers/mm.c
+++ b/rust/helpers/mm.c
@@ -48,3 +48,8 @@ __rust_helper void rust_helper_vma_end_read(struct vm_area_struct *vma)
 {
 	vma_end_read(vma);
 }
+
+__rust_helper pgprot_t rust_helper_pgprot_noncached(pgprot_t prot)
+{
+	return pgprot_noncached(prot);
+}

-- 
2.53.0