[iobuf] Allow allocation of I/O buffers with a specified alignment offset

Signed-off-by: Michael Brown <mcb30@ipxe.org>

diff --git a/src/core/iobuf.c b/src/core/iobuf.c
index c049118116711675ddb58bbf83a172f3c367d982..3f67d2f5ec0861e7456817caf2b6e36ca0448c36 100644 (file)
--- a/src/core/iobuf.c
+++ b/src/core/iobuf.c
@@ -32,31 +32,25 @@ FILE_LICENCE ( GPL2_OR_LATER );
  */
 
 /**
- * Allocate I/O buffer
+ * Allocate I/O buffer with specified alignment and offset
  *
  * @v len      Required length of buffer
+ * @v align    Physical alignment
+ * @v offset   Offset from physical alignment
  * @ret iobuf  I/O buffer, or NULL if none available
  *
- * The I/O buffer will be physically aligned to a multiple of
- * @c IOBUF_SIZE.
+ * @c align will be rounded up to the nearest power of two.
  */
-struct io_buffer * alloc_iob ( size_t len ) {
+struct io_buffer * alloc_iob_raw ( size_t len, size_t align, size_t offset ) {
        struct io_buffer *iobuf;
-       size_t align;
        void *data;
 
-       /* Pad to minimum length */
-       if ( len < IOB_ZLEN )
-               len = IOB_ZLEN;
-
        /* Align buffer length to ensure that struct io_buffer is aligned */
        len = ( len + __alignof__ ( *iobuf ) - 1 ) &
                ~( __alignof__ ( *iobuf ) - 1 );
 
-       /* Align buffer on its own size to avoid potential problems
-        * with boundary-crossing DMA.
-        */
-       align = ( 1 << fls ( len - 1 ) );
+       /* Round up alignment to the nearest power of two */
+       align = ( 1 << fls ( align - 1 ) );
 
        /* Allocate buffer plus descriptor as a single unit, unless
         * doing so will push the total size over the alignment
@@ -65,7 +59,8 @@ struct io_buffer * alloc_iob ( size_t len ) {
        if ( ( len + sizeof ( *iobuf ) ) <= align ) {
 
                /* Allocate memory for buffer plus descriptor */
-               data = malloc_dma ( len + sizeof ( *iobuf ), align );
+               data = malloc_dma_offset ( len + sizeof ( *iobuf ), align,
+                                          offset );
                if ( ! data )
                        return NULL;
                iobuf = ( data + len );
@@ -73,7 +68,7 @@ struct io_buffer * alloc_iob ( size_t len ) {
        } else {
 
                /* Allocate memory for buffer */
-               data = malloc_dma ( len, align );
+               data = malloc_dma_offset ( len, align, offset );
                if ( ! data )
                        return NULL;
 
@@ -92,6 +87,26 @@ struct io_buffer * alloc_iob ( size_t len ) {
        return iobuf;
 }
 
+/**
+ * Allocate I/O buffer
+ *
+ * @v len      Required length of buffer
+ * @ret iobuf  I/O buffer, or NULL if none available
+ *
+ * The I/O buffer will be physically aligned on its own size (rounded
+ * up to the nearest power of two).
+ */
+struct io_buffer * alloc_iob ( size_t len ) {
+
+       /* Pad to minimum length */
+       if ( len < IOB_ZLEN )
+               len = IOB_ZLEN;
+
+       /* Align buffer on its own size to avoid potential problems
+        * with boundary-crossing DMA.
+        */
+       return alloc_iob_raw ( len, len, 0 );
+}
 
 /**
  * Free I/O buffer

diff --git a/src/include/ipxe/iobuf.h b/src/include/ipxe/iobuf.h
index 8134ae76a859fe292d8a5603a4a847ff0560cf10..65a8e80da24b2ac2479bc153aa8f2ccddfe18308 100644 (file)
--- a/src/include/ipxe/iobuf.h
+++ b/src/include/ipxe/iobuf.h
@@ -210,6 +210,8 @@ static inline void iob_populate ( struct io_buffer *iobuf,
        (iobuf) = NULL;                                 \
        __iobuf; } )
 
+extern struct io_buffer * __malloc alloc_iob_raw ( size_t len, size_t align,
+                                                  size_t offset );
 extern struct io_buffer * __malloc alloc_iob ( size_t len );
 extern void free_iob ( struct io_buffer *iobuf );
 extern void iob_pad ( struct io_buffer *iobuf, size_t min_len );