Re: [NDCTL PATCH v4 2/3] cxl: Enumerate major/minor of FWCTL char device

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

Dave Jiang wrote:
> Add major/minor discovery for the FWCTL character device that is associated
> with supprting CXL Features under the cxl_memdev. Add libcxl API functions
> to retrieve the major and minor of the FWCTL character device.
> 
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
[..]
> diff --git a/cxl/lib/private.h b/cxl/lib/private.h
> index b6cd910e9335..676bf1573487 100644
> --- a/cxl/lib/private.h
> +++ b/cxl/lib/private.h
> @@ -37,6 +37,7 @@ enum cxl_fwl_loading {
>  struct cxl_endpoint;
>  struct cxl_memdev {
>  	int id, major, minor;
> +	int fwctl_major, fwctl_minor;

Unlike daxctl_dev_get_{major,minor}() which need a valid daxctl_dev,
there is no guarantee that a memdev has a fwctl capability. So I would
prefer that the helper functions are:

int cxl_fwctl_get_major(const struct cxl_fwctl *)
int cxl_fwctl_get_minor(const struct cxl_fwctl *)
struct cxl_fwctl *cxl_memdev_get_fwctl(struct cxl_memdev *)

...where obtaining that 'struct cxl_fwctl' gives you a chance to return
NULL and prevent non-sensical cxl_memdev_get_fwctl_major() against a
memdev that does not have an active fwctl portal.

It also lets you build other cxl_fwctl helper functionality around that
object.