rust: io: mem: add a generic iomem abstraction

Add a generic iomem abstraction to safely read and write ioremapped
regions. This abstraction requires a previously acquired IoRequest
instance. This makes it so that both the resource and the device match,
or, in other words, that the resource is indeed a valid resource for a
given bound device.

A subsequent patch will add the ability to retrieve IoRequest instances
from platform devices.

The reads and writes are done through IoRaw, and are thus checked either
at compile-time, if the size of the region is known at that point, or at
runtime otherwise.

Non-exclusive access to the underlying memory region is made possible to
cater to cases where overlapped regions are unavoidable.

Acked-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
Link: https://lore.kernel.org/r/20250717-topics-tyr-platform_iomem-v15-2-beca780b77e3@collabora.com
[ Add #[expect(dead_code)] to avoid a temporary warning, remove
  unnecessary OF_ID_TABLE constants in doc-tests and ignore doc-tests
  for now to avoid a temporary build failure. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/rust/helpers/io.c b/rust/helpers/io.c
index 404776cf6717..c475913c69e6 100644
--- a/rust/helpers/io.c
+++ b/rust/helpers/io.c
@@ -8,6 +8,11 @@ void __iomem *rust_helper_ioremap(phys_addr_t offset, size_t size)
 	return ioremap(offset, size);
 }
 
+void __iomem *rust_helper_ioremap_np(phys_addr_t offset, size_t size)
+{
+	return ioremap_np(offset, size);
+}
+
 void rust_helper_iounmap(void __iomem *addr)
 {
 	iounmap(addr);