kern: dma: Add DMA frame allocator

Introduce a special frame allocation utility to reserve memory for
DMA done between devices and the host.

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 47 insertions, 0 deletions

diff --git a/src/sys/include/io/dma/alloc.h b/src/sys/include/io/dma/alloc.h
new file mode 100644
index 0000000..b1034c4
--- /dev/null
+++ b/src/sys/include/io/dma/alloc.h
@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2025 Ian Marco Moffett and L5 engineers
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the project nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _DMA_ALLOC_H_
+#define _DMA_ALLOC_H_
+
+#include <sys/types.h>
+#include <vm/vm.h>
+
+/*
+ * Allocate a buffer suitable for Direct Memory
+ * Access
+ *
+ * @npages: Number of pages to allocate
+ *
+ * Returns a pointer to the buffer base on success, otherwise a value
+ * of NULL on failure.
+ */
+void *dma_alloc_pg(size_t npages);
+
+#endif  /* !_DMA_ALLOC_H_ */