From 99322fd3b37abd88867ccc3e9f60df0195730036 Mon Sep 17 00:00:00 2001
From: Michael Brown <mcb30@ipxe.org>
Date: Tue, 15 Apr 2025 20:14:03 +0100
Subject: [PATCH] [fdt] Add fdt_cells() to read cell-based properties such as
 "reg"

Add fdt_cells() to read scalar values encoded within a cell array,
reimplement fdt_u64() as a wrapper around this, and add fdt_u32() for
completeness.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
---
 src/core/fdt.c         | 92 +++++++++++++++++++++++++++++++++--------
 src/include/ipxe/fdt.h |  5 +++
 src/tests/fdt_test.c   | 94 +++++++++++++++++++++++++++---------------
 3 files changed, 140 insertions(+), 51 deletions(-)

diff --git a/src/core/fdt.c b/src/core/fdt.c
index 85394a8e0..54f930286 100644
--- a/src/core/fdt.c
+++ b/src/core/fdt.c
@@ -468,7 +468,55 @@ const char * fdt_string ( struct fdt *fdt, unsigned int offset,
 }
 
 /**
- * Find integer property
+ * Get integer property
+ *
+ * @v fdt		Device tree
+ * @v offset		Starting node offset
+ * @v name		Property name
+ * @v index		Starting cell index
+ * @v count		Number of cells (or 0 to read all remaining cells)
+ * @v value		Integer value to fill in
+ * @ret rc		Return status code
+ */
+int fdt_cells ( struct fdt *fdt, unsigned int offset, const char *name,
+		unsigned int index, unsigned int count, uint64_t *value ) {
+	struct fdt_descriptor desc;
+	const uint32_t *cell;
+	unsigned int total;
+	int rc;
+
+	/* Clear value */
+	*value = 0;
+
+	/* Find property */
+	if ( ( rc = fdt_property ( fdt, offset, name, &desc ) ) != 0 )
+		return rc;
+	cell = desc.data;
+
+	/* Determine number of cells */
+	total = ( desc.len / sizeof ( *cell ) );
+	if ( ( index > total ) || ( count > ( total - index ) ) ) {
+		DBGC ( fdt, "FDT truncated integer \"%s\"\n", name );
+		return -ERANGE;
+	}
+	if ( ! count )
+		count = ( total - index );
+	if ( count > ( sizeof ( *value ) / sizeof ( *cell ) ) ) {
+		DBGC ( fdt, "FDT overlength integer \"%s\"\n", name );
+		return -ERANGE;
+	}
+
+	/* Read value */
+	for ( cell += index ; count ; cell++, count-- ) {
+		*value <<= 32;
+		*value |= be32_to_cpu ( *cell );
+	}
+
+	return 0;
+}
+
+/**
+ * Get 64-bit integer property
  *
  * @v fdt		Device tree
  * @v offset		Starting node offset
@@ -478,32 +526,40 @@ const char * fdt_string ( struct fdt *fdt, unsigned int offset,
  */
 int fdt_u64 ( struct fdt *fdt, unsigned int offset, const char *name,
 	      uint64_t *value ) {
-	struct fdt_descriptor desc;
-	const uint8_t *data;
-	size_t remaining;
 	int rc;
 
-	/* Clear value */
-	*value = 0;
+	/* Read value */
+	if ( ( rc = fdt_cells ( fdt, offset, name, 0, 0, value ) ) != 0 )
+		return rc;
 
-	/* Find property */
-	if ( ( rc = fdt_property ( fdt, offset, name, &desc ) ) != 0 )
+	return 0;
+}
+
+/**
+ * Get 32-bit integer property
+ *
+ * @v fdt		Device tree
+ * @v offset		Starting node offset
+ * @v name		Property name
+ * @v value		Integer value to fill in
+ * @ret rc		Return status code
+ */
+int fdt_u32 ( struct fdt *fdt, unsigned int offset, const char *name,
+	      uint32_t *value ) {
+	uint64_t value64;
+	int rc;
+
+	/* Read value */
+	if ( ( rc = fdt_u64 ( fdt, offset, name, &value64 ) ) != 0 )
 		return rc;
 
 	/* Check range */
-	if ( desc.len > sizeof ( *value ) ) {
-		DBGC ( fdt, "FDT oversized integer property \"%s\"\n", name );
+	*value = value64;
+	if ( *value != value64 ) {
+		DBGC ( fdt, "FDT overlength 32-bit integer \"%s\"\n", name );
 		return -ERANGE;
 	}
 
-	/* Parse value */
-	data = desc.data;
-	remaining = desc.len;
-	while ( remaining-- ) {
-		*value <<= 8;
-		*value |= *(data++);
-	}
-
 	return 0;
 }
 
diff --git a/src/include/ipxe/fdt.h b/src/include/ipxe/fdt.h
index a41dcaa30..fb0ae7752 100644
--- a/src/include/ipxe/fdt.h
+++ b/src/include/ipxe/fdt.h
@@ -137,8 +137,13 @@ extern const char * fdt_strings ( struct fdt *fdt, unsigned int offset,
 				  const char *name, unsigned int *count );
 extern const char * fdt_string ( struct fdt *fdt, unsigned int offset,
 				 const char *name );
+extern int fdt_cells ( struct fdt *fdt, unsigned int offset, const char *name,
+		       unsigned int index, unsigned int count,
+		       uint64_t *value );
 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 int fdt_mac ( struct fdt *fdt, unsigned int offset,
 		     struct net_device *netdev );
 extern int fdt_parse ( struct fdt *fdt, struct fdt_header *hdr,
diff --git a/src/tests/fdt_test.c b/src/tests/fdt_test.c
index 738966df8..0a143ec62 100644
--- a/src/tests/fdt_test.c
+++ b/src/tests/fdt_test.c
@@ -38,10 +38,10 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 
 /** Simplified QEMU sifive_u device tree blob */
 static const uint8_t sifive_u[] = {
-	0xd0, 0x0d, 0xfe, 0xed, 0x00, 0x00, 0x05, 0x43, 0x00, 0x00, 0x00, 0x38,
-	0x00, 0x00, 0x04, 0x68, 0x00, 0x00, 0x00, 0x28, 0x00, 0x00, 0x00, 0x11,
-	0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xdb,
-	0x00, 0x00, 0x04, 0x30, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0xd0, 0x0d, 0xfe, 0xed, 0x00, 0x00, 0x05, 0x61, 0x00, 0x00, 0x00, 0x38,
+	0x00, 0x00, 0x04, 0x7c, 0x00, 0x00, 0x00, 0x28, 0x00, 0x00, 0x00, 0x11,
+	0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xe5,
+	0x00, 0x00, 0x04, 0x44, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
 	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03, 0x00, 0x00, 0x00, 0x04,
 	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x03,
@@ -127,30 +127,32 @@ static const uint8_t sifive_u[] = {
 	0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00, 0x03, 0x00, 0x00, 0x00, 0x16,
 	0x00, 0x00, 0x00, 0x1b, 0x73, 0x69, 0x66, 0x69, 0x76, 0x65, 0x2c, 0x66,
 	0x75, 0x35, 0x34, 0x30, 0x2d, 0x63, 0x30, 0x30, 0x30, 0x2d, 0x67, 0x65,
-	0x6d, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x65, 0x74, 0x68, 0x65,
-	0x72, 0x6e, 0x65, 0x74, 0x2d, 0x70, 0x68, 0x79, 0x40, 0x30, 0x00, 0x00,
-	0x00, 0x00, 0x00, 0x03, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x00, 0x69,
-	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x02,
-	0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x09,
-	0x23, 0x61, 0x64, 0x64, 0x72, 0x65, 0x73, 0x73, 0x2d, 0x63, 0x65, 0x6c,
-	0x6c, 0x73, 0x00, 0x23, 0x73, 0x69, 0x7a, 0x65, 0x2d, 0x63, 0x65, 0x6c,
-	0x6c, 0x73, 0x00, 0x63, 0x6f, 0x6d, 0x70, 0x61, 0x74, 0x69, 0x62, 0x6c,
-	0x65, 0x00, 0x6d, 0x6f, 0x64, 0x65, 0x6c, 0x00, 0x73, 0x74, 0x64, 0x6f,
-	0x75, 0x74, 0x2d, 0x70, 0x61, 0x74, 0x68, 0x00, 0x73, 0x65, 0x72, 0x69,
-	0x61, 0x6c, 0x30, 0x00, 0x65, 0x74, 0x68, 0x65, 0x72, 0x6e, 0x65, 0x74,
-	0x30, 0x00, 0x74, 0x69, 0x6d, 0x65, 0x62, 0x61, 0x73, 0x65, 0x2d, 0x66,
-	0x72, 0x65, 0x71, 0x75, 0x65, 0x6e, 0x63, 0x79, 0x00, 0x64, 0x65, 0x76,
-	0x69, 0x63, 0x65, 0x5f, 0x74, 0x79, 0x70, 0x65, 0x00, 0x72, 0x65, 0x67,
-	0x00, 0x73, 0x74, 0x61, 0x74, 0x75, 0x73, 0x00, 0x72, 0x69, 0x73, 0x63,
-	0x76, 0x2c, 0x69, 0x73, 0x61, 0x00, 0x23, 0x69, 0x6e, 0x74, 0x65, 0x72,
-	0x72, 0x75, 0x70, 0x74, 0x2d, 0x63, 0x65, 0x6c, 0x6c, 0x73, 0x00, 0x69,
-	0x6e, 0x74, 0x65, 0x72, 0x72, 0x75, 0x70, 0x74, 0x2d, 0x63, 0x6f, 0x6e,
-	0x74, 0x72, 0x6f, 0x6c, 0x6c, 0x65, 0x72, 0x00, 0x72, 0x61, 0x6e, 0x67,
-	0x65, 0x73, 0x00, 0x6c, 0x6f, 0x63, 0x61, 0x6c, 0x2d, 0x6d, 0x61, 0x63,
-	0x2d, 0x61, 0x64, 0x64, 0x72, 0x65, 0x73, 0x73, 0x00, 0x70, 0x68, 0x79,
-	0x2d, 0x68, 0x61, 0x6e, 0x64, 0x6c, 0x65, 0x00, 0x70, 0x68, 0x79, 0x2d,
-	0x6d, 0x6f, 0x64, 0x65, 0x00, 0x72, 0x65, 0x67, 0x2d, 0x6e, 0x61, 0x6d,
-	0x65, 0x73, 0x00
+	0x6d, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03, 0x00, 0x00, 0x00, 0x08,
+	0x00, 0x00, 0x00, 0xdb, 0x00, 0x00, 0x00, 0x02, 0x54, 0x0b, 0xe4, 0x00,
+	0x00, 0x00, 0x00, 0x01, 0x65, 0x74, 0x68, 0x65, 0x72, 0x6e, 0x65, 0x74,
+	0x2d, 0x70, 0x68, 0x79, 0x40, 0x30, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03,
+	0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x00, 0x69, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x02,
+	0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x09, 0x23, 0x61, 0x64, 0x64,
+	0x72, 0x65, 0x73, 0x73, 0x2d, 0x63, 0x65, 0x6c, 0x6c, 0x73, 0x00, 0x23,
+	0x73, 0x69, 0x7a, 0x65, 0x2d, 0x63, 0x65, 0x6c, 0x6c, 0x73, 0x00, 0x63,
+	0x6f, 0x6d, 0x70, 0x61, 0x74, 0x69, 0x62, 0x6c, 0x65, 0x00, 0x6d, 0x6f,
+	0x64, 0x65, 0x6c, 0x00, 0x73, 0x74, 0x64, 0x6f, 0x75, 0x74, 0x2d, 0x70,
+	0x61, 0x74, 0x68, 0x00, 0x73, 0x65, 0x72, 0x69, 0x61, 0x6c, 0x30, 0x00,
+	0x65, 0x74, 0x68, 0x65, 0x72, 0x6e, 0x65, 0x74, 0x30, 0x00, 0x74, 0x69,
+	0x6d, 0x65, 0x62, 0x61, 0x73, 0x65, 0x2d, 0x66, 0x72, 0x65, 0x71, 0x75,
+	0x65, 0x6e, 0x63, 0x79, 0x00, 0x64, 0x65, 0x76, 0x69, 0x63, 0x65, 0x5f,
+	0x74, 0x79, 0x70, 0x65, 0x00, 0x72, 0x65, 0x67, 0x00, 0x73, 0x74, 0x61,
+	0x74, 0x75, 0x73, 0x00, 0x72, 0x69, 0x73, 0x63, 0x76, 0x2c, 0x69, 0x73,
+	0x61, 0x00, 0x23, 0x69, 0x6e, 0x74, 0x65, 0x72, 0x72, 0x75, 0x70, 0x74,
+	0x2d, 0x63, 0x65, 0x6c, 0x6c, 0x73, 0x00, 0x69, 0x6e, 0x74, 0x65, 0x72,
+	0x72, 0x75, 0x70, 0x74, 0x2d, 0x63, 0x6f, 0x6e, 0x74, 0x72, 0x6f, 0x6c,
+	0x6c, 0x65, 0x72, 0x00, 0x72, 0x61, 0x6e, 0x67, 0x65, 0x73, 0x00, 0x6c,
+	0x6f, 0x63, 0x61, 0x6c, 0x2d, 0x6d, 0x61, 0x63, 0x2d, 0x61, 0x64, 0x64,
+	0x72, 0x65, 0x73, 0x73, 0x00, 0x70, 0x68, 0x79, 0x2d, 0x68, 0x61, 0x6e,
+	0x64, 0x6c, 0x65, 0x00, 0x70, 0x68, 0x79, 0x2d, 0x6d, 0x6f, 0x64, 0x65,
+	0x00, 0x72, 0x65, 0x67, 0x2d, 0x6e, 0x61, 0x6d, 0x65, 0x73, 0x00, 0x6d,
+	0x61, 0x78, 0x2d, 0x73, 0x70, 0x65, 0x65, 0x64, 0x00
 };
 
 /**
@@ -162,6 +164,7 @@ static void fdt_test_exec ( void ) {
 	struct fdt_header *hdr;
 	struct fdt fdt;
 	const char *string;
+	uint32_t u32;
 	uint64_t u64;
 	unsigned int count;
 	unsigned int offset;
@@ -194,11 +197,6 @@ static void fdt_test_exec ( void ) {
 				      &count ) ) == NULL );
 	ok ( count == 0 );
 
-	/* Verify integer properties */
-	ok ( fdt_u64 ( &fdt, 0, "#address-cells", &u64 ) == 0 );
-	ok ( u64 == 2 );
-	ok ( fdt_u64 ( &fdt, 0, "#nonexistent", &u64 ) != 0 );
-
 	/* Verify path lookup */
 	ok ( fdt_path ( &fdt, "", &offset ) == 0 );
 	ok ( offset == 0 );
@@ -214,6 +212,36 @@ static void fdt_test_exec ( void ) {
 	ok ( fdt_path ( &fdt, "/nonexistent", &offset ) != 0 );
 	ok ( fdt_path ( &fdt, "/cpus/nonexistent", &offset ) != 0 );
 
+	/* Verify 64-bit integer properties */
+	ok ( fdt_u64 ( &fdt, 0, "#address-cells", &u64 ) == 0 );
+	ok ( u64 == 2 );
+	ok ( fdt_path ( &fdt, "/soc/ethernet@10090000", &offset ) == 0 );
+	ok ( fdt_u64 ( &fdt, offset, "max-speed", &u64 ) == 0 );
+	ok ( u64 == 10000000000ULL );
+	ok ( fdt_u64 ( &fdt, offset, "#nonexistent", &u64 ) != 0 );
+
+	/* Verify 32-bit integer properties */
+	ok ( fdt_u32 ( &fdt, 0, "#address-cells", &u32 ) == 0 );
+	ok ( u32 == 2 );
+	ok ( fdt_u32 ( &fdt, 0, "#nonexistent", &u32 ) != 0 );
+	ok ( fdt_path ( &fdt, "/soc/ethernet@10090000", &offset ) == 0 );
+	ok ( fdt_u32 ( &fdt, offset, "max-speed", &u32 ) != 0 );
+
+	/* Verify cell properties */
+	ok ( fdt_path ( &fdt, "/soc/ethernet@10090000", &offset ) == 0 );
+	ok ( fdt_cells ( &fdt, offset, "reg", 4, 2, &u64 ) == 0 );
+	ok ( u64 == 0x100a0000 );
+	ok ( fdt_cells ( &fdt, offset, "reg", 6, 2, &u64 ) == 0 );
+	ok ( u64 == 0x1000 );
+	ok ( fdt_cells ( &fdt, offset, "reg", 0, 2, &u64 ) == 0 );
+	ok ( u64 == 0x10090000 );
+	ok ( fdt_cells ( &fdt, offset, "reg", 6, 0, &u64 ) == 0 );
+	ok ( u64 == 0x1000 );
+	ok ( fdt_cells ( &fdt, offset, "reg", 8, 0, &u64 ) == 0 );
+	ok ( u64 == 0 );
+	ok ( fdt_cells ( &fdt, offset, "reg", 7, 2, &u64 ) != 0 );
+	ok ( fdt_cells ( &fdt, offset, "notareg", 0, 1, &u64 ) != 0 );
+
 	/* Verify alias lookup */
 	ok ( fdt_alias ( &fdt, "serial0", &offset ) == 0 );
 	ok ( ( string = fdt_string ( &fdt, offset, "compatible" ) ) != NULL );