Re: [PATCH v6 09/14] cxl/region: Factor out code to find the root decoder

[Dan Williams <dan.j.williams@intel.com>]

Robert Richter wrote:
> In function cxl_add_to_region() there is code to determine the root
> decoder associated to an endpoint decoder. Factor out that code for
> later reuse. This has the benefit of reducing cxl_add_to_region()'s
> function complexity.
> 
> The reference count must be decremented after using the root decoder.
> cxl_find_root_decoder() is paired with the put_cxl_root_decoder
> cleanup helper that can be used for this.
[..]
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 59d0d6becbd1..45f5d2c7dfdf 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
[..]
> @@ -3384,29 +3407,17 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
>  
>  int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)
>  {
> -	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
> -	struct cxl_port *port = cxled_to_port(cxled);
> -	struct cxl_root *cxl_root __free(put_cxl_root) = find_cxl_root(port);
> +	struct cxl_root_decoder *cxlrd __free(put_cxl_root_decoder) = NULL;

Please avoid the "obj __free(...) = NULL" pattern. Per the documentation
in include/linux/cleanup.h.

>  	struct range *hpa = &cxled->cxld.hpa_range;
> -	struct cxl_decoder *cxld = &cxled->cxld;
> -	struct device *cxlrd_dev, *region_dev;
> -	struct cxl_root_decoder *cxlrd;
> +	struct device *region_dev;
>  	struct cxl_region_params *p;
>  	struct cxl_region *cxlr;
>  	bool attach = false;
>  	int rc;
>  
> -	cxlrd_dev = device_find_child(&cxl_root->port.dev, &cxld->hpa_range,
> -				      match_root_decoder_by_range);
> -	if (!cxlrd_dev) {
> -		dev_err(cxlmd->dev.parent,
> -			"%s:%s no CXL window for range %#llx:%#llx\n",
> -			dev_name(&cxlmd->dev), dev_name(&cxld->dev),
> -			cxld->hpa_range.start, cxld->hpa_range.end);
> +	cxlrd = cxl_find_root_decoder(cxled);

...i.e. always instantiate and asssign a scope-based cleanup variable in
one statement.

	cxlrd __free(put_cxl_root_decoder) = cxl_find_root_decoder(cxled);

Otherwise, this looks good.