[PATCH] libfdt: Add fdt_next_subnode() to permit easy subnode iteration

[PATCH] libfdt: Add fdt_next_subnode() to permit easy subnode iteration

[Simon Glass]

Iterating through subnodes with libfdt is a little painful to write as we
need something like this:

for (depth = 0, count = 0,
	offset = fdt_next_node(fdt, parent_offset, &depth);
     (offset >= 0) && (depth > 0);
     offset = fdt_next_node(fdt, offset, &depth)) {
	if (depth == 1) {
		/* code body */
	}
}

Using fdt_next_subnode() we can instead write this, which is shorter and
easier to get right:

for (depth = 0, offset = fdt_next_subnode(fdt, parent_offset, &depth);
     offset >= 0;
     offset = fdt_next_subnode(fdt, offset, &depth)) {
	/* code body */
}

Also, it doesn't require two levels of indentation for the loop body.

Signed-off-by: Simon Glass <sjg-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
---
 libfdt/fdt.c              | 12 ++++++
 libfdt/libfdt.h           | 17 +++++++++
 tests/Makefile.tests      |  3 +-
 tests/run_tests.sh        |  3 ++
 tests/subnode_iterate.c   | 97 +++++++++++++++++++++++++++++++++++++++++++++++
 tests/subnode_iterate.dts | 44 +++++++++++++++++++++
 6 files changed, 175 insertions(+), 1 deletion(-)
 create mode 100644 tests/subnode_iterate.c
 create mode 100644 tests/subnode_iterate.dts

diff --git a/libfdt/fdt.c b/libfdt/fdt.c
index 57faba3..9433f38 100644
--- a/libfdt/fdt.c
+++ b/libfdt/fdt.c
@@ -198,6 +198,18 @@ int fdt_next_node(const void *fdt, int offset, int *depth)
 	return offset;
 }
 
+int fdt_next_subnode(const void *fdt, int offset, int *depth)
+{
+	/* Loop until we find a direct child of the parent (depth == 1) */
+	do {
+		offset = fdt_next_node(fdt, offset, depth);
+		if (offset < 0 || *depth < 1)
+			return -FDT_ERR_NOTFOUND;
+	} while (*depth > 1);
+
+	return offset;
+}
+
 const char *_fdt_find_string(const char *strtab, int tabsize, const char *s)
 {
 	int len = strlen(s) + 1;
diff --git a/libfdt/libfdt.h b/libfdt/libfdt.h
index 130789a..edd5488 100644
--- a/libfdt/libfdt.h
+++ b/libfdt/libfdt.h
@@ -136,6 +136,23 @@ uint32_t fdt_next_tag(const void *fdt, int offset, int *nextoffset);
 
 int fdt_next_node(const void *fdt, int offset, int *depth);
 
+/**
+ * fdt_next_subnode() - get offset of next direct subnode
+ *
+ * Set depth to 0, offset to parent, then call this function repeatedly
+ * to get direct subnodes of a parent node.
+ *
+ * @fdt:	FDT blob
+ * @offset:	Set this to offset of parent for the first call. For
+ *		subsquent calls, pass in the value returns from the last
+ *		call.
+ * @depth:	Used internally to monitor depth - set this to 0 for the
+ *		first call.
+ * @return offset of next subnode, or -FDT_ERR_NOTFOUND if there are no more
+ * subnodes
+ */
+int fdt_next_subnode(const void *fdt, int offset, int *depth);
+
 /**********************************************************************/
 /* General functions                                                  */
 /**********************************************************************/
diff --git a/tests/Makefile.tests b/tests/Makefile.tests
index d59bff8..dafb618 100644
--- a/tests/Makefile.tests
+++ b/tests/Makefile.tests
@@ -20,7 +20,8 @@ LIB_TESTS_L = get_mem_rsv \
 	dtb_reverse dtbs_equal_unordered \
 	add_subnode_with_nops path_offset_aliases \
 	utilfdt_test \
-	integer-expressions
+	integer-expressions \
+	subnode_iterate
 LIB_TESTS = $(LIB_TESTS_L:%=$(TESTS_PREFIX)%)
 
 LIBTREE_TESTS_L = truncated_property
diff --git a/tests/run_tests.sh b/tests/run_tests.sh
index b56b626..b013761 100755
--- a/tests/run_tests.sh
+++ b/tests/run_tests.sh
@@ -241,6 +241,9 @@ libfdt_tests () {
 	tree1_tests_rw noppy.$basetree
     done
 
+    run_dtc_test -I dts -O dtb -o subnode_iterate.dtb subnode_iterate.dts
+    run_test subnode_iterate subnode_iterate.dtb
+
     # Tests for behaviour on various sorts of corrupted trees
     run_test truncated_property
 
diff --git a/tests/subnode_iterate.c b/tests/subnode_iterate.c
new file mode 100644
index 0000000..9a36bb6
--- /dev/null
+++ b/tests/subnode_iterate.c
@@ -0,0 +1,97 @@
+/*
+ * libfdt - Flat Device Tree manipulation
+ *	Tests that fdt_next_subnode() works as expected
+ *
+ * Copyright (C) 2013 Google, Inc
+ *
+ * Copyright (C) 2007 David Gibson, IBM Corporation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * as published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+
+#include <libfdt.h>
+
+#include "tests.h"
+#include "testdata.h"
+
+static void test_node(void *fdt, int parent_offset)
+{
+	fdt32_t subnodes;
+	const fdt32_t *prop;
+	int offset;
+	int depth;
+	int count;
+	int len;
+
+	/* This property indicates the number of subnodes to expect */
+	prop = fdt_getprop(fdt, parent_offset, "subnodes", &len);
+	if (!prop || len != sizeof(fdt32_t)) {
+		FAIL("Missing/invalid subnodes property at '%s'",
+		     fdt_get_name(fdt, parent_offset, NULL));
+	}
+	subnodes = cpu_to_fdt32(*prop);
+
+	count = 0;
+	for (depth = 0, offset = fdt_next_subnode(fdt, parent_offset, &depth);
+	     offset >= 0;
+	     offset = fdt_next_subnode(fdt, offset, &depth)) {
+		count++;
+	}
+
+	if (count != subnodes) {
+		FAIL("Node '%s': Expected %d subnodes, got %d\n",
+		     fdt_get_name(fdt, parent_offset, NULL), subnodes,
+		     count);
+	}
+}
+
+static void check_fdt_next_subnode(void *fdt)
+{
+	int depth;
+	int offset;
+	int count = 0;
+
+	for (depth = 0, offset = fdt_next_subnode(fdt, 0, &depth);
+	     offset >= 0;
+	     offset = fdt_next_subnode(fdt, offset, &depth)) {
+		test_node(fdt, offset);
+		count++;
+	}
+
+	if (count != 2)
+		FAIL("Expected %d tests, got %d\n", 2, count);
+}
+
+int main(int argc, char *argv[])
+{
+	void *fdt;
+
+	test_init(argc, argv);
+	if (argc != 2)
+		CONFIG("Usage: %s <dtb file>", argv[0]);
+
+	fdt = load_blob(argv[1]);
+	if (!fdt)
+		FAIL("No device tree available");
+
+	check_fdt_next_subnode(fdt);
+
+	PASS();
+}
diff --git a/tests/subnode_iterate.dts b/tests/subnode_iterate.dts
new file mode 100644
index 0000000..14a0d3a
--- /dev/null
+++ b/tests/subnode_iterate.dts
@@ -0,0 +1,44 @@
+/dts-v1/;
+
+/ {
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	test1 {
+		subnodes = <2>;
+		linux,phandle = <0x1>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+		PowerPC,970@0 {
+			name = "PowerPC,970";
+			device_type = "cpu";
+			reg = <0x00000000>;
+			clock-frequency = <1600000000>;
+			timebase-frequency = <33333333>;
+			linux,boot-cpu;
+			i-cache-size = <65536>;
+			d-cache-size = <32768>;
+			another-sub-node {
+				should-be-ignored;
+				yet-another {
+					should-also-be-ignored;
+				};
+			};
+		};
+
+		PowerPC,970@1 {
+			name = "PowerPC,970";
+			device_type = "cpu";
+			reg = <0x00000001>;
+			clock-frequency = <1600000000>;
+			timebase-frequency = <33333333>;
+			i-cache-size = <65536>;
+			d-cache-size = <32768>;
+		};
+	};
+
+	test2 {
+		subnodes = <0>;
+	};
+};
+
-- 
1.8.2.1

Re: [PATCH] libfdt: Add fdt_next_subnode() to permit easy subnode iteration

[David Gibson]

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On Thu, Apr 25, 2013 at 11:22:56AM -0700, Simon Glass wrote:
> Iterating through subnodes with libfdt is a little painful to write as we
> need something like this:
> 
> for (depth = 0, count = 0,
> 	offset = fdt_next_node(fdt, parent_offset, &depth);
>      (offset >= 0) && (depth > 0);
>      offset = fdt_next_node(fdt, offset, &depth)) {
> 	if (depth == 1) {
> 		/* code body */
> 	}
> }
> 
> Using fdt_next_subnode() we can instead write this, which is shorter and
> easier to get right:
> 
> for (depth = 0, offset = fdt_next_subnode(fdt, parent_offset, &depth);
>      offset >= 0;
>      offset = fdt_next_subnode(fdt, offset, &depth)) {
> 	/* code body */
> }
> 
> Also, it doesn't require two levels of indentation for the loop
> body.

I like the idea in principle.  But if you split this into
find_first_subnode() and find_next_subnode() functions, you should be
able to get rid of the requirement for the caller to provide the depth
variable.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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[PATCH v2] libfdt: Add fdt_next_subnode() to permit easy subnode iteration

[Simon Glass]

Iterating through subnodes with libfdt is a little painful to write as we
need something like this:

for (depth = 0, count = 0,
	offset = fdt_next_node(fdt, parent_offset, &depth);
     (offset >= 0) && (depth > 0);
     offset = fdt_next_node(fdt, offset, &depth)) {
	if (depth == 1) {
		/* code body */
	}
}

Using fdt_next_subnode() we can instead write this, which is shorter and
easier to get right:

for (offset = fdt_first_subnode(fdt, parent_offset);
     offset >= 0;
     offset = fdt_next_subnode(fdt, offset)) {
	/* code body */
}

Also, it doesn't require two levels of indentation for the loop body.

Signed-off-by: Simon Glass <sjg-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
---
Changes in v2:
- Use first/next pattern to avoid needing a depth parameter

 libfdt/fdt.c              | 28 ++++++++++++++
 libfdt/libfdt.h           | 22 +++++++++++
 tests/Makefile.tests      |  3 +-
 tests/run_tests.sh        |  3 ++
 tests/subnode_iterate.c   | 94 +++++++++++++++++++++++++++++++++++++++++++++++
 tests/subnode_iterate.dts | 44 ++++++++++++++++++++++
 6 files changed, 193 insertions(+), 1 deletion(-)
 create mode 100644 tests/subnode_iterate.c
 create mode 100644 tests/subnode_iterate.dts

diff --git a/libfdt/fdt.c b/libfdt/fdt.c
index 57faba3..2ce6a44 100644
--- a/libfdt/fdt.c
+++ b/libfdt/fdt.c
@@ -198,6 +198,34 @@ int fdt_next_node(const void *fdt, int offset, int *depth)
 	return offset;
 }
 
+int fdt_first_subnode(const void *fdt, int offset)
+{
+	int depth = 0;
+
+	offset = fdt_next_node(fdt, offset, &depth);
+	if (offset < 0 || depth != 1)
+		return -FDT_ERR_NOTFOUND;
+
+	return offset;
+}
+
+int fdt_next_subnode(const void *fdt, int offset)
+{
+	int depth = 1;
+
+	/*
+	 * With respect to the parent, the depth of the next subnode will be
+	 * the same as the last.
+	 */
+	do {
+		offset = fdt_next_node(fdt, offset, &depth);
+		if (offset < 0 || depth < 1)
+			return -FDT_ERR_NOTFOUND;
+	} while (depth > 1);
+
+	return offset;
+}
+
 const char *_fdt_find_string(const char *strtab, int tabsize, const char *s)
 {
 	int len = strlen(s) + 1;
diff --git a/libfdt/libfdt.h b/libfdt/libfdt.h
index 130789a..02baa84 100644
--- a/libfdt/libfdt.h
+++ b/libfdt/libfdt.h
@@ -136,6 +136,28 @@ uint32_t fdt_next_tag(const void *fdt, int offset, int *nextoffset);
 
 int fdt_next_node(const void *fdt, int offset, int *depth);
 
+/**
+ * fdt_first_subnode() - get offset of first direct subnode
+ *
+ * @fdt:	FDT blob
+ * @offset:	Offset of node to check
+ * @return offset of first subnode, or -FDT_ERR_NOTFOUND if there is none
+ */
+int fdt_first_subnode(const void *fdt, int offset);
+
+/**
+ * fdt_next_subnode() - get offset of next direct subnode
+ *
+ * After first calling fdt_first_subnode(), call this function repeatedly to
+ * get direct subnodes of a parent node.
+ *
+ * @fdt:	FDT blob
+ * @offset:	Offset of previous subnode
+ * @return offset of next subnode, or -FDT_ERR_NOTFOUND if there are no more
+ * subnodes
+ */
+int fdt_next_subnode(const void *fdt, int offset);
+
 /**********************************************************************/
 /* General functions                                                  */
 /**********************************************************************/
diff --git a/tests/Makefile.tests b/tests/Makefile.tests
index d59bff8..dafb618 100644
--- a/tests/Makefile.tests
+++ b/tests/Makefile.tests
@@ -20,7 +20,8 @@ LIB_TESTS_L = get_mem_rsv \
 	dtb_reverse dtbs_equal_unordered \
 	add_subnode_with_nops path_offset_aliases \
 	utilfdt_test \
-	integer-expressions
+	integer-expressions \
+	subnode_iterate
 LIB_TESTS = $(LIB_TESTS_L:%=$(TESTS_PREFIX)%)
 
 LIBTREE_TESTS_L = truncated_property
diff --git a/tests/run_tests.sh b/tests/run_tests.sh
index b56b626..b013761 100755
--- a/tests/run_tests.sh
+++ b/tests/run_tests.sh
@@ -241,6 +241,9 @@ libfdt_tests () {
 	tree1_tests_rw noppy.$basetree
     done
 
+    run_dtc_test -I dts -O dtb -o subnode_iterate.dtb subnode_iterate.dts
+    run_test subnode_iterate subnode_iterate.dtb
+
     # Tests for behaviour on various sorts of corrupted trees
     run_test truncated_property
 
diff --git a/tests/subnode_iterate.c b/tests/subnode_iterate.c
new file mode 100644
index 0000000..b9f379d
--- /dev/null
+++ b/tests/subnode_iterate.c
@@ -0,0 +1,94 @@
+/*
+ * libfdt - Flat Device Tree manipulation
+ *	Tests that fdt_next_subnode() works as expected
+ *
+ * Copyright (C) 2013 Google, Inc
+ *
+ * Copyright (C) 2007 David Gibson, IBM Corporation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * as published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+
+#include <libfdt.h>
+
+#include "tests.h"
+#include "testdata.h"
+
+static void test_node(void *fdt, int parent_offset)
+{
+	fdt32_t subnodes;
+	const fdt32_t *prop;
+	int offset;
+	int count;
+	int len;
+
+	/* This property indicates the number of subnodes to expect */
+	prop = fdt_getprop(fdt, parent_offset, "subnodes", &len);
+	if (!prop || len != sizeof(fdt32_t)) {
+		FAIL("Missing/invalid subnodes property at '%s'",
+		     fdt_get_name(fdt, parent_offset, NULL));
+	}
+	subnodes = cpu_to_fdt32(*prop);
+
+	count = 0;
+	for (offset = fdt_first_subnode(fdt, parent_offset);
+	     offset >= 0;
+	     offset = fdt_next_subnode(fdt, offset))
+		count++;
+
+	if (count != subnodes) {
+		FAIL("Node '%s': Expected %d subnodes, got %d\n",
+		     fdt_get_name(fdt, parent_offset, NULL), subnodes,
+		     count);
+	}
+}
+
+static void check_fdt_next_subnode(void *fdt)
+{
+	int offset;
+	int count = 0;
+
+	for (offset = fdt_first_subnode(fdt, 0);
+	     offset >= 0;
+	     offset = fdt_next_subnode(fdt, offset)) {
+		test_node(fdt, offset);
+		count++;
+	}
+
+	if (count != 2)
+		FAIL("Expected %d tests, got %d\n", 2, count);
+}
+
+int main(int argc, char *argv[])
+{
+	void *fdt;
+
+	test_init(argc, argv);
+	if (argc != 2)
+		CONFIG("Usage: %s <dtb file>", argv[0]);
+
+	fdt = load_blob(argv[1]);
+	if (!fdt)
+		FAIL("No device tree available");
+
+	check_fdt_next_subnode(fdt);
+
+	PASS();
+}
diff --git a/tests/subnode_iterate.dts b/tests/subnode_iterate.dts
new file mode 100644
index 0000000..14a0d3a
--- /dev/null
+++ b/tests/subnode_iterate.dts
@@ -0,0 +1,44 @@
+/dts-v1/;
+
+/ {
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	test1 {
+		subnodes = <2>;
+		linux,phandle = <0x1>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+		PowerPC,970@0 {
+			name = "PowerPC,970";
+			device_type = "cpu";
+			reg = <0x00000000>;
+			clock-frequency = <1600000000>;
+			timebase-frequency = <33333333>;
+			linux,boot-cpu;
+			i-cache-size = <65536>;
+			d-cache-size = <32768>;
+			another-sub-node {
+				should-be-ignored;
+				yet-another {
+					should-also-be-ignored;
+				};
+			};
+		};
+
+		PowerPC,970@1 {
+			name = "PowerPC,970";
+			device_type = "cpu";
+			reg = <0x00000001>;
+			clock-frequency = <1600000000>;
+			timebase-frequency = <33333333>;
+			i-cache-size = <65536>;
+			d-cache-size = <32768>;
+		};
+	};
+
+	test2 {
+		subnodes = <0>;
+	};
+};
+
-- 
1.8.2.1

Re: [PATCH v2] libfdt: Add fdt_next_subnode() to permit easy subnode iteration

[David Gibson]

[-- Attachment #1.1: Type: text/plain, Size: 1133 bytes --]

On Fri, Apr 26, 2013 at 05:43:31AM -0700, Simon Glass wrote:
> Iterating through subnodes with libfdt is a little painful to write as we
> need something like this:
> 
> for (depth = 0, count = 0,
> 	offset = fdt_next_node(fdt, parent_offset, &depth);
>      (offset >= 0) && (depth > 0);
>      offset = fdt_next_node(fdt, offset, &depth)) {
> 	if (depth == 1) {
> 		/* code body */
> 	}
> }
> 
> Using fdt_next_subnode() we can instead write this, which is shorter and
> easier to get right:
> 
> for (offset = fdt_first_subnode(fdt, parent_offset);
>      offset >= 0;
>      offset = fdt_next_subnode(fdt, offset)) {
> 	/* code body */
> }
> 
> Also, it doesn't require two levels of indentation for the loop body.
> 
> Signed-off-by: Simon Glass <sjg-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>

Nice!

Acked-by: David Gibson <david-xT8FGy+AXnRB3Ne2BGzF6laj5H9X9Tb+@public.gmane.org>

Jon, please apply.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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Re: [PATCH v2] libfdt: Add fdt_next_subnode() to permit easy subnode iteration

[Jon Loeliger]

> On Fri, Apr 26, 2013 at 05:43:31AM -0700, Simon Glass wrote:
> > Iterating through subnodes with libfdt is a little painful to write as we
> > need something like this:
> >
> > for (depth = 0, count = 0,
> > 	offset = fdt_next_node(fdt, parent_offset, &depth);
> >      (offset >= 0) && (depth > 0);
> >      offset = fdt_next_node(fdt, offset, &depth)) {
> > 	if (depth == 1) {
> > 		/* code body */
> > 	}
> > }
> >
> > Using fdt_next_subnode() we can instead write this, which is shorter and
> > easier to get right:
> >
> > for (offset = fdt_first_subnode(fdt, parent_offset);
> >      offset >= 0;
> >      offset = fdt_next_subnode(fdt, offset)) {
> > 	/* code body */
> > }
> >
> > Also, it doesn't require two levels of indentation for the loop body.
> >
> > Signed-off-by: Simon Glass <sjg-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
>
> Nice!
>
> Acked-by: David Gibson <david-xT8FGy+AXnRB3Ne2BGzF6laj5H9X9Tb+@public.gmane.org>
>
> Jon, please apply.

Applied.

Thanks,
jdl