Kernel: Add DMA allocate functions that are TRY-able

Add DMA allocate buffer helper functions in MemoryManager.

Kernel/Memory/MemoryManager.cpp

@@ -733,6 +733,25 @@ ErrorOr<NonnullOwnPtr<Region>> MemoryManager::allocate_contiguous_kernel_region(
     return allocate_kernel_region_with_vmobject(range, move(vmobject), name, access, cacheable);
 }
 
+ErrorOr<NonnullOwnPtr<Memory::Region>> MemoryManager::allocate_dma_buffer_page(StringView name, Memory::Region::Access access, RefPtr<Memory::PhysicalPage>& dma_buffer_page)
+{
+    dma_buffer_page = allocate_supervisor_physical_page();
+    if (dma_buffer_page.is_null())
+        return ENOMEM;
+    auto region_or_error = allocate_kernel_region(dma_buffer_page->paddr(), PAGE_SIZE, name, access);
+    return region_or_error;
+}
+
+ErrorOr<NonnullOwnPtr<Memory::Region>> MemoryManager::allocate_dma_buffer_pages(size_t size, StringView name, Memory::Region::Access access, NonnullRefPtrVector<Memory::PhysicalPage>& dma_buffer_pages)
+{
+    VERIFY(!(size % PAGE_SIZE));
+    dma_buffer_pages = allocate_contiguous_supervisor_physical_pages(size);
+    if (dma_buffer_pages.is_empty())
+        return ENOMEM;
+    auto region_or_error = allocate_kernel_region(dma_buffer_pages.first().paddr(), size, name, access);
+    return region_or_error;
+}
+
 ErrorOr<NonnullOwnPtr<Region>> MemoryManager::allocate_kernel_region(size_t size, StringView name, Region::Access access, AllocationStrategy strategy, Region::Cacheable cacheable)
 {
     VERIFY(!(size % PAGE_SIZE));

Kernel/Memory/MemoryManager.h

@@ -175,6 +175,8 @@ public:
     void deallocate_physical_page(PhysicalAddress);
 
     ErrorOr<NonnullOwnPtr<Region>> allocate_contiguous_kernel_region(size_t, StringView name, Region::Access access, Region::Cacheable = Region::Cacheable::Yes);
+    ErrorOr<NonnullOwnPtr<Memory::Region>> allocate_dma_buffer_page(StringView name, Memory::Region::Access access, RefPtr<Memory::PhysicalPage>& dma_buffer_page);
+    ErrorOr<NonnullOwnPtr<Memory::Region>> allocate_dma_buffer_pages(size_t size, StringView name, Memory::Region::Access access, NonnullRefPtrVector<Memory::PhysicalPage>& dma_buffer_pages);
     ErrorOr<NonnullOwnPtr<Region>> allocate_kernel_region(size_t, StringView name, Region::Access access, AllocationStrategy strategy = AllocationStrategy::Reserve, Region::Cacheable = Region::Cacheable::Yes);
     ErrorOr<NonnullOwnPtr<Region>> allocate_kernel_region(PhysicalAddress, size_t, StringView name, Region::Access access, Region::Cacheable = Region::Cacheable::Yes);
     ErrorOr<NonnullOwnPtr<Region>> allocate_kernel_region_with_vmobject(VMObject&, size_t, StringView name, Region::Access access, Region::Cacheable = Region::Cacheable::Yes);