[v3,04/15] device property: Introduce device_for_each_child_node_scoped()

Commit Message

Jonathan Cameron Feb. 16, 2024, 5:52 p.m. UTC

From: Jonathan Cameron <[e-mail]>

Similar to recently propose for_each_child_of_node_scoped() this
new version of the loop macro instantiates a new local
struct fwnode_handle * that uses the __free(fwnode_handle) auto
cleanup handling so that if a reference to a node is held on early
exit from the loop the reference will be released. If the loop
runs to completion, the child pointer will be NULL and no action will
be taken.

The reason this is useful is that it removes the need for
fwnode_handle_put() on early loop exits.  If there is a need
to retain the reference, then return_ptr(child) or no_free_ptr(child)
may be used to safely disable the auto cleanup.

Signed-off-by: Jonathan Cameron <[e-mail]>
---
 include/linux/property.h | 5 +++++
 1 file changed, 5 insertions(+)

Comments

Andy Shevchenko Feb. 16, 2024, 6:02 p.m. UTC | #1

On Fri, Feb 16, 2024 at 05:52:10PM +0000, Jonathan Cameron wrote:
> From: Jonathan Cameron <[e-mail]>
> 
> Similar to recently propose for_each_child_of_node_scoped() this
> new version of the loop macro instantiates a new local
> struct fwnode_handle * that uses the __free(fwnode_handle) auto
> cleanup handling so that if a reference to a node is held on early
> exit from the loop the reference will be released. If the loop
> runs to completion, the child pointer will be NULL and no action will
> be taken.
> 
> The reason this is useful is that it removes the need for
> fwnode_handle_put() on early loop exits.  If there is a need
> to retain the reference, then return_ptr(child) or no_free_ptr(child)
> may be used to safely disable the auto cleanup.

...

> +#define device_for_each_child_node_scoped(dev, child)\
> +	for (struct fwnode_handle *child __free(fwnode_handle) = \
> +	     device_get_next_child_node(dev, NULL); child; \
> +	     child = device_get_next_child_node(dev, child))

You haven't changed the indentation of backslashes...

Jonathan Cameron Feb. 17, 2024, 4:31 p.m. UTC | #2

On Fri, 16 Feb 2024 20:02:49 +0200
Andy Shevchenko <[e-mail]> wrote:

> On Fri, Feb 16, 2024 at 05:52:10PM +0000, Jonathan Cameron wrote:
> > From: Jonathan Cameron <[e-mail]>
> > 
> > Similar to recently propose for_each_child_of_node_scoped() this
> > new version of the loop macro instantiates a new local
> > struct fwnode_handle * that uses the __free(fwnode_handle) auto
> > cleanup handling so that if a reference to a node is held on early
> > exit from the loop the reference will be released. If the loop
> > runs to completion, the child pointer will be NULL and no action will
> > be taken.
> > 
> > The reason this is useful is that it removes the need for
> > fwnode_handle_put() on early loop exits.  If there is a need
> > to retain the reference, then return_ptr(child) or no_free_ptr(child)
> > may be used to safely disable the auto cleanup.  
> 
> ...
> 
> > +#define device_for_each_child_node_scoped(dev, child)\
> > +	for (struct fwnode_handle *child __free(fwnode_handle) = \
> > +	     device_get_next_child_node(dev, NULL); child; \
> > +	     child = device_get_next_child_node(dev, child))  
> 
> You haven't changed the indentation of backslashes...
> 

I've managed to send out a stale version as definitely did update
that.  Sorry for the noise!

Ah found it - I managed to commit it on patch 15 not this one.

Will move it and send a v4.

Patch

diff --git a/include/linux/property.h b/include/linux/property.h
index 9e67c3c4df6e..421ccfd43fb1 100644
--- a/include/linux/property.h
+++ b/include/linux/property.h
@@ -182,6 +182,11 @@  struct fwnode_handle *device_get_next_child_node(const struct device *dev,
 	for (child = device_get_next_child_node(dev, NULL); child;	\
 	     child = device_get_next_child_node(dev, child))
 
+#define device_for_each_child_node_scoped(dev, child)\
+	for (struct fwnode_handle *child __free(fwnode_handle) = \
+	     device_get_next_child_node(dev, NULL); child; \
+	     child = device_get_next_child_node(dev, child))
+
 struct fwnode_handle *fwnode_get_named_child_node(const struct fwnode_handle *fwnode,
 						  const char *childname);
 struct fwnode_handle *device_get_named_child_node(const struct device *dev,