Re: [RFC PATCH 01/13] device property: Add cleanup.h based fwnode_handle_put() scope based cleanup.

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Mon, Jan 01, 2024 at 05:25:59PM +0000, Jonathan Cameron wrote:
> From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> 
> This allows the following
> 
> struct fwnode_handle *child __free(kfree) = NULL;
> 
> device_for_each_child_node(dev, child) {
> 	if (false)
> 		return -EINVAL;
> }
> 
> without the fwnode_handle_put() call which tends to complicate early
> exits from such loops and lead to resource leak bugs.
> 
> Can also be used where the fwnode_handle was obtained from a call
> such as fwnode_find_reference() as it will safely do nothing if
> IS_ERR() is true.

...

>  struct fwnode_handle *fwnode_handle_get(struct fwnode_handle *fwnode);
>  void fwnode_handle_put(struct fwnode_handle *fwnode);
> +DEFINE_FREE(fwnode_handle, struct fwnode_handle *, fwnode_handle_put(_T))

In GPIO we have something similar and PeterZ explained there why if (_T) is
important, hence this should be

DEFINE_FREE(fwnode_handle, struct fwnode_handle *, if (_T) fwnode_handle_put(_T))

or even

DEFINE_FREE(fwnode_handle, struct fwnode_handle *, if (!IS_ERR_OR_NULL(_T)) fwnode_handle_put(_T))

as we accept in many calls an error pointer as unset / undefined firmware node
handle.


-- 
With Best Regards,
Andy Shevchenko