[fdt] Generalise access to "reg" property

The "reg" property is also used by non-device nodes, such as the nodes
describing the system memory map.

Provide generalised functionality for parsing the "#address-cells",
"#size-cells", and "reg" properties.

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

src/core/fdt.c

@@ -563,6 +563,111 @@ int fdt_u32 ( struct fdt *fdt, unsigned int offset, const char *name,
 	return 0;
 }
 
+/**
+ * Get region cell size specification
+ *
+ * @v fdt		Device tree
+ * @v offset		Starting (parent) node offset
+ * @v regs		Region cell size specification to fill in
+ *
+ * Note that #address-cells and #size-cells are defined on the
+ * immediate parent node, rather than on the node with the "reg"
+ * property itself.
+ */
+void fdt_reg_cells ( struct fdt *fdt, unsigned int offset,
+		     struct fdt_reg_cells *regs ) {
+	int rc;
+
+	/* Read #address-cells, if present */
+	if ( ( rc = fdt_u32 ( fdt, offset, "#address-cells",
+			      &regs->address_cells ) ) != 0 ) {
+		regs->address_cells = FDT_DEFAULT_ADDRESS_CELLS;
+	}
+
+	/* Read #size-cells, if present */
+	if ( ( rc = fdt_u32 ( fdt, offset, "#size-cells",
+			      &regs->size_cells ) ) != 0 ) {
+		regs->size_cells = FDT_DEFAULT_SIZE_CELLS;
+	}
+
+	/* Calculate stride */
+	regs->stride = ( regs->address_cells + regs->size_cells );
+}
+
+/**
+ * Get number of regions
+ *
+ * @v fdt		Device tree
+ * @v offset		Starting node offset
+ * @v regs		Region cell size specification
+ * @ret count		Number of regions, or negative error
+ */
+int fdt_reg_count ( struct fdt *fdt, unsigned int offset,
+		    struct fdt_reg_cells *regs ) {
+	struct fdt_descriptor desc;
+	const uint32_t *cell;
+	unsigned int count;
+	int rc;
+
+	/* Find property */
+	if ( ( rc = fdt_property ( fdt, offset, "reg", &desc ) ) != 0 )
+		return rc;
+
+	/* Determine number of regions */
+	count = ( desc.len / ( regs->stride * sizeof ( *cell ) ) );
+	return count;
+}
+
+/**
+ * Get region address
+ *
+ * @v fdt		Device tree
+ * @v offset		Starting node offset
+ * @v regs		Region cell size specification
+ * @v index		Region index
+ * @v address		Region starting address to fill in
+ * @ret rc		Return status code
+ */
+int fdt_reg_address ( struct fdt *fdt, unsigned int offset,
+		      struct fdt_reg_cells *regs, unsigned int index,
+		      uint64_t *address ) {
+	unsigned int cell = ( index * regs->stride );
+	int rc;
+
+	/* Read relevant portion of region array */
+	if ( ( rc = fdt_cells ( fdt, offset, "reg", cell, regs->address_cells,
+				address ) ) != 0 ) {
+		return rc;
+	}
+
+	return 0;
+}
+
+/**
+ * Get region size
+ *
+ * @v fdt		Device tree
+ * @v offset		Starting node offset
+ * @v regs		Region cell size specification
+ * @v index		Region index
+ * @v size		Region size to fill in
+ * @ret rc		Return status code
+ */
+int fdt_reg_size ( struct fdt *fdt, unsigned int offset,
+		   struct fdt_reg_cells *regs, unsigned int index,
+		   uint64_t *size ) {
+	unsigned int cell = ( ( index * regs->stride ) + regs->address_cells );
+	int rc;
+
+	/* Read relevant portion of region array */
+	if ( ( rc = fdt_cells ( fdt, offset, "reg", cell, regs->size_cells,
+				size ) ) != 0 ) {
+		return rc;
+	}
+
+	return 0;
+}
+
 /**
  * Get MAC address from property
  *

src/drivers/bus/devtree.c

@@ -56,27 +56,25 @@ void * dt_ioremap ( struct dt_device *dt, unsigned int offset,
 		    unsigned int index, size_t len ) {
 	struct dt_device *parent =
 		container_of ( dt->dev.parent, struct dt_device, dev );
+	struct fdt_reg_cells *regs = &parent->regs;
 	uint64_t address;
 	uint64_t size;
-	unsigned int cell;
 	void *io_addr;
 	int rc;
 
 	/* Read address */
-	cell = ( index * ( parent->address_cells + parent->size_cells ) );
+	if ( ( rc = fdt_reg_address ( &sysfdt, offset, regs, index,
-	if ( ( rc = fdt_cells ( &sysfdt, offset, "reg", cell,
+				      &address ) ) != 0 ) {
-				parent->address_cells, &address ) ) != 0 ) {
 		DBGC ( dt, "DT %s could not read region %d address: %s\n",
 		       dt->path, index, strerror ( rc ) );
 		return NULL;
 	}
-	cell += parent->address_cells;
 
 	/* Read size (or assume sufficient, if tree specifies no sizes) */
 	size = len;
-	if ( parent->size_cells &&
+	if ( regs->size_cells &&
-	     ( rc = fdt_cells ( &sysfdt, offset, "reg", cell,
+	     ( ( rc = fdt_reg_size ( &sysfdt, offset, regs, index,
-				parent->size_cells, &size ) ) != 0 ) {
+				     &size ) ) != 0 ) ) {
 		DBGC ( dt, "DT %s could not read region %d size: %s\n",
 		       dt->path, index, strerror ( rc ) );
 		return NULL;
@@ -225,14 +223,7 @@ static int dt_probe_node ( struct dt_device *parent, unsigned int offset,
 	list_add_tail ( &dt->dev.siblings, &dt->dev.parent->children );
 
 	/* Read #address-cells and #size-cells, if present */
-	if ( ( rc = fdt_u32 ( &sysfdt, offset, "#address-cells",
+	fdt_reg_cells ( &sysfdt, offset, &dt->regs );
-			      &dt->address_cells ) ) != 0 ) {
-		dt->address_cells = DT_DEFAULT_ADDRESS_CELLS;
-	}
-	if ( ( rc = fdt_u32 ( &sysfdt, offset, "#size-cells",
-			      &dt->size_cells ) ) != 0 ) {
-		dt->size_cells = DT_DEFAULT_SIZE_CELLS;
-	}
 
 	/* Probe device */
 	if ( ( rc = dt_probe ( dt, offset ) ) != 0 )

src/include/ipxe/devtree.h

@@ -11,6 +11,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 
 #include <ipxe/device.h>
 #include <ipxe/dma.h>
+#include <ipxe/fdt.h>
 
 /** A devicetree device */
 struct dt_device {
@@ -25,18 +26,10 @@ struct dt_device {
 	/** Driver-private data */
 	void *priv;
 
-	/** Number of address cells for child devices */
+	/** Register cell size specification */
-	uint32_t address_cells;
+	struct fdt_reg_cells regs;
-	/** Number of size cells for child devices */
-	uint32_t size_cells;
 };
 
-/** Default number of address cells, if not specified */
-#define DT_DEFAULT_ADDRESS_CELLS 2
-
-/** Default number of size cells, if not specified */
-#define DT_DEFAULT_SIZE_CELLS 1
-
 /** A devicetree driver */
 struct dt_driver {
 	/** Driver name */

src/include/ipxe/fdt.h

@@ -124,6 +124,22 @@ struct fdt_descriptor {
 	int depth;
 };
 
+/** A device tree region cell size specification */
+struct fdt_reg_cells {
+	/** Number of address cells */
+	uint32_t address_cells;
+	/** Number of size cells */
+	uint32_t size_cells;
+	/** Number of address cells plus number of size cells */
+	unsigned int stride;
+};
+
+/** Default number of address cells, if not specified */
+#define FDT_DEFAULT_ADDRESS_CELLS 2
+
+/** Default number of size cells, if not specified */
+#define FDT_DEFAULT_SIZE_CELLS 1
+
 extern struct image_tag fdt_image __image_tag;
 extern struct fdt sysfdt;
 
@@ -144,6 +160,16 @@ extern int fdt_u64 ( struct fdt *fdt, unsigned int offset, const char *name,
 		     uint64_t *value );
 extern int fdt_u32 ( struct fdt *fdt, unsigned int offset, const char *name,
 		     uint32_t *value );
+extern void fdt_reg_cells ( struct fdt *fdt, unsigned int offset,
+			    struct fdt_reg_cells *regs );
+extern int fdt_reg_count ( struct fdt *fdt, unsigned int offset,
+			   struct fdt_reg_cells *regs );
+extern int fdt_reg_address ( struct fdt *fdt, unsigned int offset,
+			     struct fdt_reg_cells *regs, unsigned int index,
+			     uint64_t *address );
+extern int fdt_reg_size ( struct fdt *fdt, unsigned int offset,
+			  struct fdt_reg_cells *regs, unsigned int index,
+			  uint64_t *size );
 extern int fdt_mac ( struct fdt *fdt, unsigned int offset,
 		     struct net_device *netdev );
 extern int fdt_parse ( struct fdt *fdt, struct fdt_header *hdr,