From: Michael Brown <mcb30@ipxe.org>
Date: Thu, 7 Aug 2025 14:41:42 +0000 (+0100)
Subject: [fdt] Provide fdt_reg() for unsized single-entry regions
X-Git-Url: http://git.ipfire.org/gitweb/gitweb.cgi?a=commitdiff_plain;h=88ba0117649bd8ec711ec0d799acb649284dc492;p=thirdparty%2Fipxe.git

[fdt] Provide fdt_reg() for unsized single-entry regions

Many region types (e.g. I2C bus addresses) can only ever contain a
single region with no size cells specified.  Provide fdt_reg() to
reduce boilerplate in this common use case.

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

diff --git a/src/core/fdt.c b/src/core/fdt.c
index ae723213b..08adb166e 100644
--- a/src/core/fdt.c
+++ b/src/core/fdt.c
@@ -732,6 +732,29 @@ void fdt_reg_cells ( struct fdt *fdt, unsigned int offset,
 	regs->stride = ( regs->address_cells + regs->size_cells );
 }
 
+/**
+ * Get parent region cell size specification
+ *
+ * @v fdt		Device tree
+ * @v offset		Starting node offset
+ * @v regs		Region cell size specification to fill in
+ * @ret rc		Return status code
+ */
+int fdt_parent_reg_cells ( struct fdt *fdt, unsigned int offset,
+			   struct fdt_reg_cells *regs ) {
+	unsigned int parent;
+	int rc;
+
+	/* Get parent node */
+	if ( ( rc = fdt_parent ( fdt, offset, &parent ) ) != 0 )
+		return rc;
+
+	/* Read #address-cells and #size-cells, if present */
+	fdt_reg_cells ( fdt, parent, regs );
+
+	return 0;
+}
+
 /**
  * Get number of regions
  *
@@ -806,6 +829,32 @@ int fdt_reg_size ( struct fdt *fdt, unsigned int offset,
 	return 0;
 }
 
+/**
+ * Get unsized single-entry region address
+ *
+ * @v fdt		Device tree
+ * @v offset		Starting node offset
+ * @v address		Region address to fill in
+ * @ret rc		Return status code
+ *
+ * Many region types (e.g. I2C bus addresses) can only ever contain a
+ * single region with no size cells specified.
+ */
+int fdt_reg ( struct fdt *fdt, unsigned int offset, uint64_t *region ) {
+	struct fdt_reg_cells regs;
+	int rc;
+
+	/* Get parent region cell size specification */
+	if ( ( rc = fdt_parent_reg_cells ( fdt, offset, &regs ) ) != 0 )
+		return rc;
+
+	/* Get first region address */
+	if ( ( rc = fdt_reg_address ( fdt, offset, &regs, 0, region ) ) != 0 )
+		return rc;
+
+	return 0;
+}
+
 /**
  * Get MAC address from property
  *
diff --git a/src/drivers/bus/devtree.c b/src/drivers/bus/devtree.c
index 32ab1c2cb..f71ad1ea4 100644
--- a/src/drivers/bus/devtree.c
+++ b/src/drivers/bus/devtree.c
@@ -52,22 +52,18 @@ static struct dt_driver dt_node_driver __dt_driver;
 void * dt_ioremap ( struct dt_device *dt, unsigned int offset,
 		    unsigned int index, size_t len ) {
 	struct fdt_reg_cells regs;
-	unsigned int parent;
 	uint64_t address;
 	uint64_t size;
 	void *io_addr;
 	int rc;
 
-	/* Get parent node */
-	if ( ( rc = fdt_parent ( &sysfdt, offset, &parent ) ) != 0 ) {
-		DBGC ( dt, "DT %s could not locate parent: %s\n",
+	/* Get parent region cell size specification */
+	if ( ( rc = fdt_parent_reg_cells ( &sysfdt, offset, &regs ) ) != 0 ) {
+		DBGC ( dt, "DT %s could not get region cell sizes: %s\n",
 		       dt->name, strerror ( rc ) );
 		return NULL;
 	}
 
-	/* Read #address-cells and #size-cells, if present */
-	fdt_reg_cells ( &sysfdt, parent, &regs );
-
 	/* Read address */
 	if ( ( rc = fdt_reg_address ( &sysfdt, offset, &regs, index,
 				      &address ) ) != 0 ) {
diff --git a/src/include/ipxe/fdt.h b/src/include/ipxe/fdt.h
index eec02c5b3..e951aea59 100644
--- a/src/include/ipxe/fdt.h
+++ b/src/include/ipxe/fdt.h
@@ -190,6 +190,8 @@ extern int fdt_u32 ( struct fdt *fdt, unsigned int offset, const char *name,
 extern uint32_t fdt_phandle ( struct fdt *fdt, unsigned int offset );
 extern void fdt_reg_cells ( struct fdt *fdt, unsigned int offset,
 			    struct fdt_reg_cells *regs );
+extern int fdt_parent_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,
@@ -198,6 +200,7 @@ extern int fdt_reg_address ( struct fdt *fdt, unsigned int offset,
 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_reg ( struct fdt *fdt, unsigned int offset, uint64_t *region );
 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,