It's not fully correct to take a const parameter pointer to a struct
and return a non-const pointer to a member of that struct.

Instead, introduce a const version of the dev_fwnode() API which takes
and returns const pointers and use it where it's applicable.

With this, convert dev_fwnode() to be a macro wrapper on top of const
and non-const APIs that chooses one based on the type.

Suggested-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Fixes: aade55c86033 ("device property: Add const qualifier to device_get_match_data() parameter")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
---
 drivers/base/property.c  | 11 +++++++++--
 include/linux/property.h |  7 ++++++-
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/base/property.c b/drivers/base/property.c
index 4d6278a84868..d77302d28566 100644
--- a/drivers/base/property.c
+++ b/drivers/base/property.c
@@ -17,12 +17,19 @@
 #include <linux/property.h>
 #include <linux/phy.h>
 
-struct fwnode_handle *dev_fwnode(const struct device *dev)
+struct fwnode_handle *__dev_fwnode(struct device *dev)
 {
 	return IS_ENABLED(CONFIG_OF) && dev->of_node ?
 		of_fwnode_handle(dev->of_node) : dev->fwnode;
 }
-EXPORT_SYMBOL_GPL(dev_fwnode);
+EXPORT_SYMBOL_GPL(__dev_fwnode);
+
+const struct fwnode_handle *__dev_fwnode_const(const struct device *dev)
+{
+	return IS_ENABLED(CONFIG_OF) && dev->of_node ?
+		of_fwnode_handle(dev->of_node) : dev->fwnode;
+}
+EXPORT_SYMBOL_GPL(__dev_fwnode_const);
 
 /**
  * device_property_present - check if a property of a device is present
diff --git a/include/linux/property.h b/include/linux/property.h
index 117cc200c656..587b5b666b5b 100644
--- a/include/linux/property.h
+++ b/include/linux/property.h
@@ -32,7 +32,12 @@ enum dev_dma_attr {
 	DEV_DMA_COHERENT,
 };
 
-struct fwnode_handle *dev_fwnode(const struct device *dev);
+const struct fwnode_handle *__dev_fwnode_const(const struct device *dev);
+struct fwnode_handle *__dev_fwnode(struct device *dev);
+#define dev_fwnode(dev)							\
+	_Generic((dev),							\
+		 const struct device *: __dev_fwnode_const,	\
+		 struct device *: __dev_fwnode)(dev)
 
 bool device_property_present(struct device *dev, const char *propname);
 int device_property_read_u8_array(struct device *dev, const char *propname,
-- 
2.35.1

On Tue, Oct 04, 2022 at 12:21:25PM +0300, Andy Shevchenko wrote:
> It's not fully correct to take a const parameter pointer to a struct
> and return a non-const pointer to a member of that struct.
> 
> Instead, introduce a const version of the dev_fwnode() API which takes
> and returns const pointers and use it where it's applicable.
> 
> With this, convert dev_fwnode() to be a macro wrapper on top of const
> and non-const APIs that chooses one based on the type.

Hmm... it missed the device_get_match_data() implementation (reverse) change
somehow. And it still compiles to me, probably I rebased wrongly and the hunk
went to another patch. I'll investigate and resend as v4 the fixed version.

-- 
With Best Regards,
Andy Shevchenko

On Tue, Oct 04, 2022 at 12:34:56PM +0300, Andy Shevchenko wrote:
> On Tue, Oct 04, 2022 at 12:21:25PM +0300, Andy Shevchenko wrote:
> > It's not fully correct to take a const parameter pointer to a struct
> > and return a non-const pointer to a member of that struct.
> > 
> > Instead, introduce a const version of the dev_fwnode() API which takes
> > and returns const pointers and use it where it's applicable.
> > 
> > With this, convert dev_fwnode() to be a macro wrapper on top of const
> > and non-const APIs that chooses one based on the type.
> 
> Hmm... it missed the device_get_match_data() implementation (reverse) change
> somehow. And it still compiles to me, probably I rebased wrongly and the hunk
> went to another patch. I'll investigate and resend as v4 the fixed version.

Ah, sorry, I mixed this with previous version of the patch here, so everything
is fine in v3!

-- 
With Best Regards,
Andy Shevchenko