[v3,11/13] of: add property iteration helpers

Commit Message

Stephen Warren Aug. 25, 2011, 11:43 p.m. UTC

This patch adds macros for_each_u32_property_value and
for_each_string_property_value, which iterate over an array of values
within a device-tree property. Usage is for example:

struct of_iter_string_prop iter;
for_each_string_property_value(iter, np, "pins")
        printk("Got value %s\n", iter.value);

Signed-off-by: Stephen Warren <[e-mail]>
---
 include/linux/of_iter_prop.h |  135 ++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 135 insertions(+), 0 deletions(-)
 create mode 100644 include/linux/of_iter_prop.h

Comments

Jamie Iles Aug. 26, 2011, 9:26 a.m. UTC | #1

On Thu, Aug 25, 2011 at 05:43:42PM -0600, Stephen Warren wrote:
> This patch adds macros for_each_u32_property_value and
> for_each_string_property_value, which iterate over an array of values
> within a device-tree property. Usage is for example:
> 
> struct of_iter_string_prop iter;
> for_each_string_property_value(iter, np, "pins")
>         printk("Got value %s\n", iter.value);
> 
> Signed-off-by: Stephen Warren <[e-mail]>

Nicely implemented!  For the !CONFIG_OF case, I *think* that 
of_iter_u32_prop and of_iter_string_prop can be empty struct's, but I 
wouldn't want to bet money on that!

Reviewed-by: Jamie Iles <[e-mail]>

Stephen Warren Aug. 26, 2011, 3:59 p.m. UTC | #2

Jamie Iles wrote at Friday, August 26, 2011 3:27 AM:
> On Thu, Aug 25, 2011 at 05:43:42PM -0600, Stephen Warren wrote:
> > This patch adds macros for_each_u32_property_value and
> > for_each_string_property_value, which iterate over an array of values
> > within a device-tree property. Usage is for example:
> >
> > struct of_iter_string_prop iter;
> > for_each_string_property_value(iter, np, "pins")
> >         printk("Got value %s\n", iter.value);
> >
> > Signed-off-by: Stephen Warren <[e-mail]>
> 
> Nicely implemented!

Thanks!

> For the !CONFIG_OF case, I *think* that
> of_iter_u32_prop and of_iter_string_prop can be empty struct's, but I
> wouldn't want to bet money on that!

Empty structs themselves certainly did compile OK, but the code that
uses these macros references iter.value directly, and isn't under #ifdef
CONFIG_OF, so that field has to exist.

I suppose an alternative would be to add an accessor function:

struct of_iter_string_prop iter;
for_each_string_property_value(iter, np, "pins")
        printk("Got value %s\n", of_iter_string_value(iter));

which would return NULL/"" when !CONFIG_OF, and hence allow iter.value
to be removed too. Do you think that's a good approach? It'd be easy to
implement.

Jamie Iles Aug. 26, 2011, 4:16 p.m. UTC | #3

On Fri, Aug 26, 2011 at 08:59:44AM -0700, Stephen Warren wrote:
> Jamie Iles wrote at Friday, August 26, 2011 3:27 AM:
> > For the !CONFIG_OF case, I *think* that
> > of_iter_u32_prop and of_iter_string_prop can be empty struct's, but I
> > wouldn't want to bet money on that!
> 
> Empty structs themselves certainly did compile OK, but the code that
> uses these macros references iter.value directly, and isn't under #ifdef
> CONFIG_OF, so that field has to exist.
> 
> I suppose an alternative would be to add an accessor function:
> 
> struct of_iter_string_prop iter;
> for_each_string_property_value(iter, np, "pins")
>         printk("Got value %s\n", of_iter_string_value(iter));
> 
> which would return NULL/"" when !CONFIG_OF, and hence allow iter.value
> to be removed too. Do you think that's a good approach? It'd be easy to
> implement.

I think I prefer what you have now rather than a separate accessor, but 
I'm happy either way!

Jamie

Patch

diff --git a/include/linux/of_iter_prop.h b/include/linux/of_iter_prop.h
new file mode 100644
index 0000000..c7fb2bf
--- /dev/null
+++ b/include/linux/of_iter_prop.h
@@ -0,0 +1,135 @@ 
+/*
+ * Copyright (c) 2011 NVIDIA Inc.
+ *
+ * Iterate over properties that store arrays.
+ *
+ * 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.
+ */
+#ifndef __OF_ITER_PROP_H__
+#define __OF_ITER_PROP_H__
+
+#include <linux/of.h>
+
+#ifdef CONFIG_OF
+struct of_iter_u32_prop {
+	const struct property *prop;
+	int len;
+	const __be32 *pvalue;
+	u32 value;
+};
+
+static inline void of_iter_u32_next(struct of_iter_u32_prop *iter)
+{
+	if (iter->len < 0)
+		return;
+
+	iter->value = be32_to_cpup(iter->pvalue++);
+	iter->len--;
+}
+
+static inline void of_iter_u32_init(struct of_iter_u32_prop *iter,
+				    const struct device_node *np,
+				    const char *name)
+{
+	iter->prop = of_find_property(np, name, &iter->len);
+	if (!iter->prop) {
+		iter->len = -1;
+		return;
+	}
+
+	iter->pvalue = iter->prop->value;
+	if (!iter->pvalue) {
+		iter->len = -1;
+		return;
+	}
+
+	iter->len /= sizeof(*iter->pvalue);
+
+	of_iter_u32_next(iter);
+}
+
+static inline bool of_iter_u32_test(struct of_iter_u32_prop *iter)
+{
+	return iter->len >= 0;
+}
+
+#define for_each_u32_property_value(iter, np, prop_name) \
+	for (of_iter_u32_init(&iter, np, prop_name); \
+	     of_iter_u32_test(&iter); \
+	     of_iter_u32_next(&iter))
+
+struct of_iter_string_prop {
+	const struct property *prop;
+	int len;
+	const char *value;
+	const char *after;
+};
+
+static inline void of_iter_string_init(struct of_iter_string_prop *iter,
+				       const struct device_node *np,
+				       const char *name)
+{
+	iter->prop = of_find_property(np, name, &iter->len);
+	if (!iter->prop) {
+		iter->value = NULL;
+		return;
+	}
+
+	iter->value = iter->prop->value;
+	if (!iter->value)
+		return;
+
+	iter->after = iter->value + iter->len;
+}
+
+static inline bool of_iter_string_test(struct of_iter_string_prop *iter)
+{
+	if (!iter->value)
+		return false;
+
+	return iter->value < iter->after;
+}
+
+static inline void of_iter_string_next(struct of_iter_string_prop *iter)
+{
+	int len;
+
+	if (!iter->value)
+		return;
+
+	len = strnlen(iter->value, iter->len);
+	iter->len -= len;
+	iter->value += len + 1;
+}
+
+#define for_each_string_property_value(iter, np, prop_name) \
+	for (of_iter_string_init(&iter, np, prop_name); \
+	     of_iter_string_test(&iter); \
+	     of_iter_string_next(&iter))
+
+#else
+struct of_iter_u32_prop {
+	u32 value;
+};
+
+#define for_each_u32_property_value(iter, np, prop_name) \
+	while (0)
+
+struct of_iter_string_prop {
+	const char *value;
+};
+
+#define for_each_string_property_value(iter, np, prop_name) \
+	while (0)
+
+#endif /* CONFIG_OF */
+
+#endif /* __OF_ITER_PROP_H__ */