[U-Boot] [PATCH v5 6/6] fdt: add decode helper library

[Simon Glass]

This library provides useful functions to drivers which want to use
the fdt to control their operation. Functions are provided to:

- look up and enumerate a device type (for example assigning i2c bus 0,
     i2c bus 1, etc.)
- decode basic types from the fdt, like addresses and integers

While this library is not strictly necessary, it helps to minimise the
changes to a driver, in order to make it work under fdt control. Less
code is required, and so the barrier to switch drivers over is lower.

Additional functions to read arrays and GPIOs could be made available
here also.

Signed-off-by: Simon Glass <sjg at chromium.org>
---
Changes in v2:
- Add example proposed decode helper library

Changes in v3:
- Simplify decode library to remove provide only primitive functions
- Remove i2c decode function
- Rename fdt_decode to fdtdec, since it will be used a lot
- Moved fdt_decode.c to /lib
- Export almost all functions from fdtdec, to allow widespread use
- Remove use of FDT_ERR_MISSING which is not strictly needed now

Changes in v4:
- Add assert on sprintf() string length
- Rename addr_t to fdt_addr_t to make it more fdt-specific
- Remove gpio.h header in fdtdec.c which is not needed yet

Changes in v5:
- Corrected const nit in fdtdec.c missed in v4

 include/fdtdec.h |  122 ++++++++++++++++++++++++++++++++++++++++++++++++++
 lib/Makefile     |    1 +
 lib/fdtdec.c     |  131 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 254 insertions(+), 0 deletions(-)
 create mode 100644 include/fdtdec.h
 create mode 100644 lib/fdtdec.c

diff --git a/include/fdtdec.h b/include/fdtdec.h
new file mode 100644
index 0000000..ae36f9c
--- /dev/null
+++ b/include/fdtdec.h
@@ -0,0 +1,122 @@
+/*
+ * Copyright (c) 2011 The Chromium OS Authors.
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+
+/*
+ * This file contains convenience functions for decoding useful and
+ * enlightening information from FDTs. It is intended to be used by device
+ * drivers and board-specific code within U-Boot. It aims to reduce the
+ * amount of FDT munging required within U-Boot itself, so that driver code
+ * changes to support FDT are minimized.
+ */
+
+#include <libfdt.h>
+
+/*
+ * A typedef for a physical address. Note that fdt data is always big
+ * endian even on a litle endian machine.
+ */
+#ifdef CONFIG_PHYS_64BIT
+typedef u64 fdt_addr_t;
+#define FDT_ADDR_T_NONE (-1ULL)
+#define fdt_addr_to_cpu(reg) be64_to_cpu(reg)
+#else
+typedef u32 fdt_addr_t;
+#define FDT_ADDR_T_NONE (-1U)
+#define fdt_addr_to_cpu(reg) be32_to_cpu(reg)
+#endif
+
+/* Information obtained about memory from the FDT */
+struct fdt_memory {
+	fdt_addr_t start;
+	fdt_addr_t end;
+};
+
+/**
+ * Compat types that we know about and for which we might have drivers.
+ * Each is named COMPAT_<dir>_<filename> where <dir> is the directory
+ * within drivers.
+ */
+enum fdt_compat_id {
+	COMPAT_UNKNOWN,
+
+	COMPAT_COUNT,
+};
+
+/**
+ * Find the next numbered alias for a peripheral. This is used to enumerate
+ * all the peripherals of a certain type.
+ *
+ * Do the first call with *upto = 0. Assuming /aliases/<name>0 exists then
+ * this function will return a pointer to the node the alias points to, and
+ * then update *upto to 1. Next time you call this function, the next node
+ * will be returned.
+ *
+ * All nodes returned will match the compatible ID, as it is assumed that
+ * all peripherals use the same driver.
+ *
+ * @param blob		FDT blob to use
+ * @param name		Root name of alias to search for
+ * @param id		Compatible ID to look for
+ * @return offset of next compatible node, or -FDT_ERR_NOTFOUND if no more
+ */
+int fdtdec_next_alias(const void *blob, const char *name,
+		enum fdt_compat_id id, int *upto);
+
+/**
+ * Look up an address property in a node and return it as an address.
+ * The property must hold either one address with no trailing data or
+ * one address with a length. This is only tested on 32-bit machines.
+ *
+ * @param blob	FDT blob
+ * @param node	node to examine
+ * @param prop_name	name of property to find
+ * @return address, if found, or FDT_ADDR_T_NONE if not
+ */
+fdt_addr_t fdtdec_get_addr(const void *blob, int node,
+		const char *prop_name);
+
+/**
+ * Look up a 32-bit integer property in a node and return it. The property
+ * must have at least 4 bytes of data. The value of the first cell is
+ * returned.
+ *
+ * @param blob	FDT blob
+ * @param node	node to examine
+ * @param prop_name	name of property to find
+ * @param default_val	default value to return if the property is not found
+ * @return integer value, if found, or default_val if not
+ */
+s32 fdtdec_get_int(const void *blob, int node, const char *prop_name,
+		s32 default_val);
+
+/**
+ * Checks whether a node is enabled.
+ * This looks for a 'status' property. If this exists, then returns 1 if
+ * the status is 'ok' and 0 otherwise. If there is no status property,
+ * it returns the default value.
+ *
+ * @param blob	FDT blob
+ * @param node	node to examine
+ * @param default_val	default value to return if no 'status' property exists
+ * @return integer value 0/1, if found, or default_val if not
+ */
+int fdtdec_get_is_enabled(const void *blob, int node, int default_val);
diff --git a/lib/Makefile b/lib/Makefile
index 884f64c..3b901c9 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -38,6 +38,7 @@ COBJS-y += crc16.o
 COBJS-y += crc32.o
 COBJS-y += display_options.o
 COBJS-y += errno.o
+COBJS-$(CONFIG_OF_CONTROL) += fdtdec.o
 COBJS-$(CONFIG_GZIP) += gunzip.o
 COBJS-y += hashtable.o
 COBJS-$(CONFIG_LMB) += lmb.o
diff --git a/lib/fdtdec.c b/lib/fdtdec.c
new file mode 100644
index 0000000..d0f2cb8
--- /dev/null
+++ b/lib/fdtdec.c
@@ -0,0 +1,131 @@
+/*
+ * Copyright (c) 2011 The Chromium OS Authors.
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#include <common.h>
+#include <serial.h>
+#include <libfdt.h>
+#include <fdtdec.h>
+
+/*
+ * Here are the type we know about. One day we might allow drivers to
+ * register. For now we just put them here. The COMPAT macro allows us to
+ * turn this into a sparse list later, and keeps the ID with the name.
+ */
+#define COMPAT(id, name) name
+static const char * const compat_names[COMPAT_COUNT] = {
+};
+
+/**
+ * Look in the FDT for an alias with the given name and return its node.
+ *
+ * @param blob	FDT blob
+ * @param name	alias name to look up
+ * @return node offset if found, or an error code < 0 otherwise
+ */
+static int find_alias_node(const void *blob, const char *name)
+{
+	const char *path;
+	int alias_node;
+
+	debug("find_alias_node: %s\n", name);
+	alias_node = fdt_path_offset(blob, "/aliases");
+	if (alias_node < 0)
+		return alias_node;
+	path = fdt_getprop(blob, alias_node, name, NULL);
+	if (!path)
+		return -FDT_ERR_NOTFOUND;
+	return fdt_path_offset(blob, path);
+}
+
+fdt_addr_t fdtdec_get_addr(const void *blob, int node,
+		const char *prop_name)
+{
+	const fdt_addr_t *cell;
+	int len;
+
+	debug("get_addr: %s\n", prop_name);
+	cell = fdt_getprop(blob, node, prop_name, &len);
+	if (cell && (len == sizeof(fdt_addr_t) ||
+			len == sizeof(fdt_addr_t) * 2))
+		return fdt_addr_to_cpu(*cell);
+	return FDT_ADDR_T_NONE;
+}
+
+s32 fdtdec_get_int(const void *blob, int node, const char *prop_name,
+		s32 default_val)
+{
+	const s32 *cell;
+	int len;
+
+	debug("get_size: %s\n", prop_name);
+	cell = fdt_getprop(blob, node, prop_name, &len);
+	if (cell && len >= sizeof(s32))
+		return fdt32_to_cpu(cell[0]);
+	return default_val;
+}
+
+int fdtdec_get_is_enabled(const void *blob, int node, int default_val)
+{
+	const char *cell;
+
+	cell = fdt_getprop(blob, node, "status", NULL);
+	if (cell)
+		return 0 == strcmp(cell, "ok");
+	return default_val;
+}
+
+enum fdt_compat_id fd_dec_lookup(const void *blob, int node)
+{
+	enum fdt_compat_id id;
+
+	/* Search our drivers */
+	for (id = COMPAT_UNKNOWN; id < COMPAT_COUNT; id++)
+		if (0 == fdt_node_check_compatible(blob, node,
+				compat_names[id]))
+			return id;
+	return COMPAT_UNKNOWN;
+}
+
+int fdtdec_next_compatible(const void *blob, int node,
+		enum fdt_compat_id id)
+{
+	return fdt_node_offset_by_compatible(blob, node, compat_names[id]);
+}
+
+int fdtdec_next_alias(const void *blob, const char *name,
+		enum fdt_compat_id id, int *upto)
+{
+#define MAX_STR_LEN 20
+	char str[MAX_STR_LEN + 20];
+	int node, err;
+
+	/* snprintf() is not available */
+	assert(strlen(name) < MAX_STR_LEN);
+	sprintf(str, "%.*s%d", MAX_STR_LEN, name, *upto);
+	(*upto)++;
+	node = find_alias_node(blob, str);
+	if (node < 0)
+		return node;
+	err = fdt_node_check_compatible(blob, node, compat_names[id]);
+	if (err < 0)
+		return err;
+	return err ? -FDT_ERR_NOTFOUND : node;
+}
-- 
1.7.3.1