Add the io section for LoongArch in OSTD

ostd/src/arch/loongarch/io.rs

@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: MPL-2.0
+
+use alloc::vec::Vec;
+
+use crate::{boot::memory_region::MemoryRegionType, io::IoMemAllocatorBuilder};
+
+/// Initializes the allocatable MMIO area based on the LoongArch memory
+/// distribution map.
+///
+/// Here we consider all the holes (filtering usable RAM) in the physical
+/// address space as MMIO regions.
+pub(super) fn construct_io_mem_allocator_builder() -> IoMemAllocatorBuilder {
+    let regions = &crate::boot::EARLY_INFO.get().unwrap().memory_regions;
+    let mut reserved_filter = regions
+        .iter()
+        .filter(|r| {
+            r.typ() != MemoryRegionType::Unknown
+                && r.typ() != MemoryRegionType::Reserved
+                && r.typ() != MemoryRegionType::Framebuffer
+        })
+        .collect::<Vec<_>>();
+    reserved_filter.sort_by_key(|r| r.base());
+
+    let mut ranges = Vec::new();
+    let mut current_address = 0;
+    for region in reserved_filter {
+        let base = region.base();
+        let size = region.len();
+
+        if base > current_address {
+            ranges.push(current_address..base);
+        }
+        current_address = current_address.max(base + size);
+    }
+    if current_address < usize::MAX {
+        ranges.push(current_address..usize::MAX);
+    }
+
+    // SAFETY: The range is guaranteed not to access physical memory.
+    unsafe { IoMemAllocatorBuilder::new(ranges) }
+}