Re: [Xen-devel] [PATCH v3 16/17] FDT: Add a helper to get specified name subnode

[Shannon Zhao]

On 2016/1/26 20:11, Stefano Stabellini wrote:
> On Sat, 23 Jan 2016, Shannon Zhao wrote:
>> > From: Shannon Zhao 
>> > 
>> > Sometimes it needs to check if there is a node in FDT by full path.
>> > Introduce this helper to get the specified name subnode if it exists.
>> > 
>> > Signed-off-by: Shannon Zhao 
>> > ---
>> > CC: Rob Herring 
>> > ---
>> >  drivers/of/fdt.c   | 35 +++
>> >  include/linux/of_fdt.h |  2 ++
>> >  2 files changed, 37 insertions(+)
>> > 
>> > diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
>> > index 655f79d..112ec16 100644
>> > --- a/drivers/of/fdt.c
>> > +++ b/drivers/of/fdt.c
>> > @@ -645,6 +645,41 @@ int __init of_scan_flat_dt(int (*it)(unsigned long 
>> > node,
>> >  }
>> >  
>> >  /**
>> > + * of_get_flat_dt_subnode_by_name - get subnode of specified node by name
>> > + *
>> > + * @node: the parent node
>> > + * @uname: the name of subnode
>> > + * @return offset of the subnode, or -FDT_ERR_NOTFOUND if there is none
>> > + */
>> > +
>> > +int of_get_flat_dt_subnode_by_name(unsigned long node, const char *uname)
>> > +{
>> > +  const void *blob = initial_boot_params;
>> > +  int offset;
>> > +  const char *pathp;
>> > +
>> > +  /* Find first subnode if it exists */
>> > +  offset = fdt_first_subnode(blob, node);
>> > +  if (offset < 0)
>> > +  return -FDT_ERR_NOTFOUND;
>> > +  pathp = fdt_get_name(blob, offset, NULL);
>> > +  if (strncmp(pathp, uname, strlen(uname)) == 0)
>> > +  return offset;
> Wouldn't this check succeed even if uname is "uefi" and the node
> name is actually "uefi"?  You might have to use strcmp.
> 
Ah, yes. Will fix this.

> 
>> > +  /* Find other subnodes */
>> > +  do {
>> > +  offset = fdt_next_subnode(blob, offset);
>> > +  if (offset < 0)
>> > +  return -FDT_ERR_NOTFOUND;
>> > +  pathp = fdt_get_name(blob, offset, NULL);
>> > +  if (strncmp(pathp, uname, strlen(uname)) == 0)
>> > +  return offset;
>> > +  } while (offset >= 0);
> Rather than writing the name check twice, I think it would be best to
> code this loop as:
> 
> for (offset = fdt_first_subnode(blob, offset);
>  offset >= 0;
>  offset = fdt_next_subnode(blob, offset)) {
> 
>  /* do name check */
> 
> 
> 
Thanks for your suggestion. Will change this.

-- 
Shannon


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Re: [Xen-devel] [PATCH v3 16/17] FDT: Add a helper to get specified name subnode

[Stefano Stabellini]

On Sat, 23 Jan 2016, Shannon Zhao wrote:
> From: Shannon Zhao 
> 
> Sometimes it needs to check if there is a node in FDT by full path.
> Introduce this helper to get the specified name subnode if it exists.
> 
> Signed-off-by: Shannon Zhao 
> ---
> CC: Rob Herring 
> ---
>  drivers/of/fdt.c   | 35 +++
>  include/linux/of_fdt.h |  2 ++
>  2 files changed, 37 insertions(+)
> 
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index 655f79d..112ec16 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -645,6 +645,41 @@ int __init of_scan_flat_dt(int (*it)(unsigned long node,
>  }
>  
>  /**
> + * of_get_flat_dt_subnode_by_name - get subnode of specified node by name
> + *
> + * @node: the parent node
> + * @uname: the name of subnode
> + * @return offset of the subnode, or -FDT_ERR_NOTFOUND if there is none
> + */
> +
> +int of_get_flat_dt_subnode_by_name(unsigned long node, const char *uname)
> +{
> + const void *blob = initial_boot_params;
> + int offset;
> + const char *pathp;
> +
> + /* Find first subnode if it exists */
> + offset = fdt_first_subnode(blob, node);
> + if (offset < 0)
> + return -FDT_ERR_NOTFOUND;
> + pathp = fdt_get_name(blob, offset, NULL);
> + if (strncmp(pathp, uname, strlen(uname)) == 0)
> + return offset;

Wouldn't this check succeed even if uname is "uefi" and the node
name is actually "uefi"?  You might have to use strcmp.


> + /* Find other subnodes */
> + do {
> + offset = fdt_next_subnode(blob, offset);
> + if (offset < 0)
> + return -FDT_ERR_NOTFOUND;
> + pathp = fdt_get_name(blob, offset, NULL);
> + if (strncmp(pathp, uname, strlen(uname)) == 0)
> + return offset;
> + } while (offset >= 0);

Rather than writing the name check twice, I think it would be best to
code this loop as:

for (offset = fdt_first_subnode(blob, offset);
 offset >= 0;
 offset = fdt_next_subnode(blob, offset)) {

 /* do name check */



> + return -FDT_ERR_NOTFOUND;
> +}
> +
> +/**
>   * of_get_flat_dt_root - find the root node in the flat blob
>   */
>  unsigned long __init of_get_flat_dt_root(void)
> diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
> index df9ef38..fc28162 100644
> --- a/include/linux/of_fdt.h
> +++ b/include/linux/of_fdt.h
> @@ -52,6 +52,8 @@ extern char __dtb_end[];
>  extern int of_scan_flat_dt(int (*it)(unsigned long node, const char *uname,
>int depth, void *data),
>  void *data);
> +extern int of_get_flat_dt_subnode_by_name(unsigned long node,
> +   const char *uname);
>  extern const void *of_get_flat_dt_prop(unsigned long node, const char *name,
>  int *size);
>  extern int of_flat_dt_is_compatible(unsigned long node, const char *name);
> -- 
> 2.0.4
> 
> 

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[Xen-devel] [PATCH v3 16/17] FDT: Add a helper to get specified name subnode

[Shannon Zhao]

From: Shannon Zhao 

Sometimes it needs to check if there is a node in FDT by full path.
Introduce this helper to get the specified name subnode if it exists.

Signed-off-by: Shannon Zhao 
---
CC: Rob Herring 
---
 drivers/of/fdt.c   | 35 +++
 include/linux/of_fdt.h |  2 ++
 2 files changed, 37 insertions(+)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 655f79d..112ec16 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -645,6 +645,41 @@ int __init of_scan_flat_dt(int (*it)(unsigned long node,
 }
 
 /**
+ * of_get_flat_dt_subnode_by_name - get subnode of specified node by name
+ *
+ * @node: the parent node
+ * @uname: the name of subnode
+ * @return offset of the subnode, or -FDT_ERR_NOTFOUND if there is none
+ */
+
+int of_get_flat_dt_subnode_by_name(unsigned long node, const char *uname)
+{
+   const void *blob = initial_boot_params;
+   int offset;
+   const char *pathp;
+
+   /* Find first subnode if it exists */
+   offset = fdt_first_subnode(blob, node);
+   if (offset < 0)
+   return -FDT_ERR_NOTFOUND;
+   pathp = fdt_get_name(blob, offset, NULL);
+   if (strncmp(pathp, uname, strlen(uname)) == 0)
+   return offset;
+
+   /* Find other subnodes */
+   do {
+   offset = fdt_next_subnode(blob, offset);
+   if (offset < 0)
+   return -FDT_ERR_NOTFOUND;
+   pathp = fdt_get_name(blob, offset, NULL);
+   if (strncmp(pathp, uname, strlen(uname)) == 0)
+   return offset;
+   } while (offset >= 0);
+
+   return -FDT_ERR_NOTFOUND;
+}
+
+/**
  * of_get_flat_dt_root - find the root node in the flat blob
  */
 unsigned long __init of_get_flat_dt_root(void)
diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
index df9ef38..fc28162 100644
--- a/include/linux/of_fdt.h
+++ b/include/linux/of_fdt.h
@@ -52,6 +52,8 @@ extern char __dtb_end[];
 extern int of_scan_flat_dt(int (*it)(unsigned long node, const char *uname,
 int depth, void *data),
   void *data);
+extern int of_get_flat_dt_subnode_by_name(unsigned long node,
+ const char *uname);
 extern const void *of_get_flat_dt_prop(unsigned long node, const char *name,
   int *size);
 extern int of_flat_dt_is_compatible(unsigned long node, const char *name);
-- 
2.0.4



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