In function cxl_add_to_region() there is code to determine a root
decoder's region. Factor that code out. This is in preparation to
further rework and simplify function cxl_add_to_region().

The reference count must be decremented after using the region.
cxl_find_region_by_range() is paired with the put_cxl_region cleanup
helper that can be used for this.

Signed-off-by: Robert Richter <rrichter@amd.com>
Reviewed-by: Gregory Price <gourry@gourry.net>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Fabio M. De Francesco <fabio.m.de.francesco@linux.intel.com>
Tested-by: Gregory Price <gourry@gourry.net>
---
 drivers/cxl/core/region.c | 26 ++++++++++++++++----------
 drivers/cxl/cxl.h         |  1 +
 2 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 45f5d2c7dfdf..8fdf03058b2f 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -3405,13 +3405,25 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
 	return cxlr;
 }
 
+static struct cxl_region *
+cxl_find_region_by_range(struct cxl_root_decoder *cxlrd, struct range *hpa)
+{
+	struct device *region_dev;
+
+	region_dev = device_find_child(&cxlrd->cxlsd.cxld.dev, hpa,
+				       match_region_by_range);
+	if (!region_dev)
+		return NULL;
+
+	return to_cxl_region(region_dev);
+}
+
 int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)
 {
 	struct cxl_root_decoder *cxlrd __free(put_cxl_root_decoder) = NULL;
+	struct cxl_region *cxlr __free(put_cxl_region) = NULL;
 	struct range *hpa = &cxled->cxld.hpa_range;
-	struct device *region_dev;
 	struct cxl_region_params *p;
-	struct cxl_region *cxlr;
 	bool attach = false;
 	int rc;
 
@@ -3424,13 +3436,9 @@ int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)
 	 * one does the construction and the others add to that.
 	 */
 	mutex_lock(&cxlrd->range_lock);
-	region_dev = device_find_child(&cxlrd->cxlsd.cxld.dev, hpa,
-				       match_region_by_range);
-	if (!region_dev) {
+	cxlr = cxl_find_region_by_range(cxlrd, hpa);
+	if (!cxlr)
 		cxlr = construct_region(cxlrd, cxled);
-		region_dev = &cxlr->dev;
-	} else
-		cxlr = to_cxl_region(region_dev);
 	mutex_unlock(&cxlrd->range_lock);
 
 	rc = PTR_ERR_OR_ZERO(cxlr);
@@ -3455,8 +3463,6 @@ int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)
 				p->res);
 	}
 
-	put_device(region_dev);
-
 	return rc;
 }
 EXPORT_SYMBOL_NS_GPL(cxl_add_to_region, "CXL");
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 371f9dcfb61a..ba08b77b65da 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -741,6 +741,7 @@ struct cxl_root *find_cxl_root(struct cxl_port *port);
 DEFINE_FREE(put_cxl_root, struct cxl_root *, if (_T) put_device(&_T->port.dev))
 DEFINE_FREE(put_cxl_port, struct cxl_port *, if (!IS_ERR_OR_NULL(_T)) put_device(&_T->dev))
 DEFINE_FREE(put_cxl_root_decoder, struct cxl_root_decoder *, if (!IS_ERR_OR_NULL(_T)) put_device(&_T->cxlsd.cxld.dev))
+DEFINE_FREE(put_cxl_region, struct cxl_region *, if (!IS_ERR_OR_NULL(_T)) put_device(&_T->dev))
 
 int devm_cxl_enumerate_ports(struct cxl_memdev *cxlmd);
 void cxl_bus_rescan(void);
-- 
2.39.5

Robert Richter wrote:
> In function cxl_add_to_region() there is code to determine a root
> decoder's region. Factor that code out. This is in preparation to
> further rework and simplify function cxl_add_to_region().
> 
> The reference count must be decremented after using the region.
> cxl_find_region_by_range() is paired with the put_cxl_region cleanup
> helper that can be used for this.
> 
> Signed-off-by: Robert Richter <rrichter@amd.com>
> Reviewed-by: Gregory Price <gourry@gourry.net>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> Reviewed-by: Dan Williams <dan.j.williams@intel.com>
> Reviewed-by: Alison Schofield <alison.schofield@intel.com>
> Reviewed-by: Fabio M. De Francesco <fabio.m.de.francesco@linux.intel.com>
> Tested-by: Gregory Price <gourry@gourry.net>
> ---
>  drivers/cxl/core/region.c | 26 ++++++++++++++++----------
>  drivers/cxl/cxl.h         |  1 +
>  2 files changed, 17 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 45f5d2c7dfdf..8fdf03058b2f 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -3405,13 +3405,25 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
>  	return cxlr;
>  }
>  
> +static struct cxl_region *
> +cxl_find_region_by_range(struct cxl_root_decoder *cxlrd, struct range *hpa)
> +{
> +	struct device *region_dev;
> +
> +	region_dev = device_find_child(&cxlrd->cxlsd.cxld.dev, hpa,
> +				       match_region_by_range);
> +	if (!region_dev)
> +		return NULL;
> +
> +	return to_cxl_region(region_dev);
> +}
> +
>  int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)
>  {
>  	struct cxl_root_decoder *cxlrd __free(put_cxl_root_decoder) = NULL;
> +	struct cxl_region *cxlr __free(put_cxl_region) = NULL;

Another instance of the "obj __free(...) = NULL" anti-pattern to clean
up. The reason it is an anti-pattern is because it risks mixing up the
assignment order with the declaration order leading to subtle bugs.

Scope-based cleanup should always be exempted from "x-mas" tree
declaration cosmetics.