[RFC][PATCHv6++ 01/13] of: introduce of_property_for_earch_phandle_with_args()
Hiroshi Doyu
hdoyu at nvidia.com
Thu Nov 28 07:58:18 EST 2013
Stephen Warren <swarren at wwwdotorg.org> wrote @ Thu, 21 Nov 2013 19:57:00 +0100:
> On 11/21/2013 10:17 AM, Hiroshi Doyu wrote:
> > Iterating over a property containing a list of phandles with arguments
> > is a common operation for device drivers. This patch adds a new
> > of_property_for_each_phandle_with_args() macro to make the iteration
> > simpler.
> >
> > Signed-off-by: Hiroshi Doyu <hdoyu at nvidia.com>
> > ---
> > v6+:
> > Use the description, which Grant Likely proposed, to be full enough
> > that a future reader can figure out why a patch was written.
> > http://lists.linuxfoundation.org/pipermail/iommu/2013-November/007062.html
>
> This new version only addresses one of the concerns that Grant had,
> namely the commit message.
>
> > diff --git a/include/linux/of.h b/include/linux/of.h
>
> > +#define of_property_for_each_phandle_with_args(np, list, cells, i, args) \
> > + for (i = 0; !of_parse_phandle_with_args(np, list, cells, i, args); i++)
> > +
>
> Grant also wanted the actual implementation fixed so that it wasn't so
> inefficient.
>
> What this current patch does is basically:
>
> for every entry in the property:
> for every entry in the property before the current index:
> parse the phandle+specifier
>
> That's roughly O(n^2). (n is # entries in the property)
>
> Instead, what should happen is:
>
> for every entry in the property:
> parse the phandle+specifier
> yield the result
>
> That's roughly O(n).
>
> In other words, an implementation more along the lines of
> include/linux/of.h's:
>
> #define of_property_for_each_u32(np, propname, prop, p, u) \
> for (prop = of_find_property(np, propname, NULL), \
> p = of_prop_next_u32(prop, NULL, &u); \
> p; \
> p = of_prop_next_u32(prop, p, &u))
>
> ... so you'd need functions like of_prop_first_specifier() and
> of_prop_next_specifier(), and perhaps some associated set of state
> variables, perhaps with all the state wrapped into a single struct for
> simplicity.
Although I couldn't invent any struct to hold params and state here,
I'd like you to review the following interface is ok or not.
At first, I thought to refactor __of_parse_phandle_with_args() but
it's a bit highly optimized by Stephen and it looked a bit hard to
refactor without perf regressions. Instread, I introduced 2 new
functions "of_parse_{first,next}_phandle_with_args()" to parse
phandles.
If this interface is ok, I'll include this into the next v7 series.
-----8<-----8<-----8<-----8<-----8<-----8<-----8<-----8<-----8<-----
From: Hiroshi Doyu <hdoyu at nvidia.com>
Iterating over a property containing a list of phandles with arguments
is a common operation for device drivers. This patch adds a new
of_property_for_each_phandle_with_args() macro to make the iteration
simpler.
Introduced "of_parse_{first,next}_phandle_with_args()", where "const
__be32 **list" is used to hold the next list to be processed as a
state pramameter, and both "of_parse_{first,next}_phandle_with_args()"
returns the remaining list in the number of cell(4 byte). If any error
happens, "list" is set NULL not to proceed the rest.
Signed-off-by: Hiroshi Doyu <hdoyu at nvidia.com>
---
v6++:
Optimized to avoid O(n^2), suggested by Stephen Warren.
http://lists.linuxfoundation.org/pipermail/iommu/2013-November/007066.html
v6+:
Use the description, which Grant Likely proposed, to be full enough
that a future reader can figure out why a patch was written.
v5:
New patch for v5.
Signed-off-by: Hiroshi Doyu <hdoyu at nvidia.com>
---
drivers/of/base.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/of.h | 52 ++++++++++++++++++++++++++++++++++
2 files changed, 134 insertions(+)
diff --git a/drivers/of/base.c b/drivers/of/base.c
index f807d0e..3e29b10 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -1201,6 +1201,88 @@ void of_print_phandle_args(const char *msg, const struct of_phandle_args *args)
printk("\n");
}
+int __of_parse_next_phandle_with_args(const __be32 **plist,
+ const char *cells_name, int cell_count,
+ struct of_phandle_args *out_args)
+{
+ phandle phandle;
+ int i, count = 0, err;
+ struct device_node *dn;
+ const __be32 *list;
+
+ BUG_ON(!out_args);
+ BUG_ON(!cells_name && !cell_count);
+
+ /*
+ * "*plist" should hold phandle, and it's updated to the next
+ * phandle at return if no error.
+ */
+ list = *plist;
+ out_args->np = NULL;
+
+ phandle = be32_to_cpup(list);
+ if (!phandle)
+ goto err_out;
+
+ dn = of_find_node_by_phandle(phandle);
+ if (!dn)
+ goto err_out;
+
+ if (cells_name) {
+ err = of_property_read_u32(dn, cells_name, &count);
+ if (err)
+ goto err_out;
+ } else {
+ count = cell_count;
+ }
+
+ out_args->np = dn;
+ out_args->args_count = count;
+ for (i = 0; i < count; i++)
+ out_args->args[i] = be32_to_cpup(list + 1 + i);
+
+ *plist = list + count + 1; /* update to the next list */
+ return count + 1;
+
+err_out:
+ *plist = NULL;
+ return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(__of_parse_next_phandle_with_args);
+
+int __of_parse_first_phandle_with_args(const struct device_node *np,
+ const __be32 **out_list,
+ const char *list_name,
+ const char *cells_name,
+ int cell_count,
+ struct of_phandle_args *out_args)
+{
+ int rem, count;
+ const __be32 *list;
+
+ list = of_get_property(np, list_name, &rem);
+ if (!list)
+ goto err_out;
+
+ rem /= sizeof(*list);
+ if (!rem)
+ goto err_out;
+
+ count = __of_parse_next_phandle_with_args(&list, cells_name,
+ cell_count, out_args);
+ if (!list)
+ goto err_out;
+
+ rem -= count;
+ *out_list = list; /* update to the next list */
+ return rem;
+
+err_out:
+ *out_list = NULL;
+ return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(__of_parse_first_phandle_with_args);
+
static int __of_parse_phandle_with_args(const struct device_node *np,
const char *list_name,
const char *cells_name,
diff --git a/include/linux/of.h b/include/linux/of.h
index 276c546..9f15622 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -303,6 +303,35 @@ extern int of_parse_phandle_with_fixed_args(const struct device_node *np,
extern int of_count_phandle_with_args(const struct device_node *np,
const char *list_name, const char *cells_name);
+extern int __of_parse_first_phandle_with_args(const struct device_node *np,
+ const __be32 **out_list,
+ const char *list_name,
+ const char *cells_name,
+ int cell_count,
+ struct of_phandle_args *out_args);
+
+extern int __of_parse_next_phandle_with_args(const __be32 **plist,
+ const char *cells_name,
+ int cell_count,
+ struct of_phandle_args *out_args);
+
+static inline int of_parse_first_phandle_with_args(const struct device_node *np,
+ const __be32 **out_list,
+ const char *list_name,
+ const char *cells_name,
+ struct of_phandle_args *out_args)
+{
+ return __of_parse_first_phandle_with_args(np, out_list, list_name,
+ cells_name, 0, out_args);
+}
+
+static inline int of_parse_next_phandle_with_args(const __be32 **plist,
+ const char *cells_name,
+ struct of_phandle_args *out_args)
+{
+ return __of_parse_next_phandle_with_args(plist, cells_name, 0, out_args);
+}
+
extern void of_alias_scan(void * (*dt_alloc)(u64 size, u64 align));
extern int of_alias_get_id(struct device_node *np, const char *stem);
@@ -527,6 +556,24 @@ static inline int of_count_phandle_with_args(struct device_node *np,
return -ENOSYS;
}
+static inline int __of_parse_first_phandle_with_args(
+ const struct device_node *np, const __be32 **out_list,
+ const char *list_name, const char *cells_name, int cell_count,
+ struct of_phandle_args *out_args)
+{
+ *out_list = NULL;
+ return -ENOSYS;
+}
+
+
+static inline int __of_parse_next_phandle_with_args(
+ const __be32 **plist, const char *cells_name, int cell_count,
+ struct of_phandle_args *out_args)
+{
+ *plist = NULL;
+ return -ENOSYS;
+}
+
static inline int of_alias_get_id(struct device_node *np, const char *stem)
{
return -ENOSYS;
@@ -613,6 +660,11 @@ static inline int of_property_read_u32(const struct device_node *np,
s; \
s = of_prop_next_string(prop, s))
+#define of_property_for_each_phandle_with_args(node, list, list_name, cells_name, rem, args) \
+ for (rem = of_parse_first_phandle_with_args(node, &list, list_name, cells_name, &args); \
+ list && rem >= 0; \
+ rem -= of_parse_next_phandle_with_args(&list, cells_name, &args))
+
#if defined(CONFIG_PROC_FS) && defined(CONFIG_PROC_DEVICETREE)
extern void proc_device_tree_add_node(struct device_node *, struct proc_dir_entry *);
extern void proc_device_tree_add_prop(struct proc_dir_entry *pde, struct property *prop);
--
1.8.1.5
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