Commit 172738bb authored by Dan Williams's avatar Dan Williams
Browse files

cxl/port: Link the 'parent_dport' in portX/ and endpointX/ sysfs 



Similar to the justification in:

1b58b4ca ("cxl/port: Record parent dport when adding ports")

...userspace wants to know the routing information for ports for
calculating the memdev order for region creation among other things.
Cache the information the kernel discovers at enumeration time in a
'parent_dport' attribute to save userspace the time of trawling sysfs
to recover the same information.

Reviewed-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/167124082375.1626103.6047000000121298560.stgit@dwillia2-xfh.jf.intel.com


Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent af3ea9ab

Documentation/ABI/testing/sysfs-bus-cxl

+15 −0
Original line number Diff line number Diff line
@@ -90,6 +90,21 @@ Description: 
		capability.





What:		/sys/bus/cxl/devices/{port,endpoint}X/parent_dport

Date:		January, 2023

KernelVersion:	v6.3

Contact:	linux-cxl@vger.kernel.org

Description:

		(RO) CXL port objects are instantiated for each upstream port in

		a CXL/PCIe switch, and for each endpoint to map the

		corresponding memory device into the CXL port hierarchy. When a

		descendant CXL port (switch or endpoint) is enumerated it is

		useful to know which 'dport' object in the parent CXL port

		routes to this descendant. The 'parent_dport' symlink points to

		the device representing the downstream port of a CXL switch that

		routes to {port,endpoint}X.





What:		/sys/bus/cxl/devices/portX/dportY

Date:		June, 2021

KernelVersion:	v5.14

drivers/cxl/core/port.c

+29 −0
Original line number Diff line number Diff line
@@ -583,6 +583,29 @@ static int devm_cxl_link_uport(struct device *host, struct cxl_port *port) 
	return devm_add_action_or_reset(host, cxl_unlink_uport, port);

}



static void cxl_unlink_parent_dport(void *_port)

{

	struct cxl_port *port = _port;



	sysfs_remove_link(&port->dev.kobj, "parent_dport");

}



static int devm_cxl_link_parent_dport(struct device *host,

				      struct cxl_port *port,

				      struct cxl_dport *parent_dport)

{

	int rc;



	if (!parent_dport)

		return 0;



	rc = sysfs_create_link(&port->dev.kobj, &parent_dport->dport->kobj,

			       "parent_dport");

	if (rc)

		return rc;

	return devm_add_action_or_reset(host, cxl_unlink_parent_dport, port);

}



static struct lock_class_key cxl_port_key;



static struct cxl_port *cxl_port_alloc(struct device *uport,
@@ -692,6 +715,10 @@ static struct cxl_port *__devm_cxl_add_port(struct device *host, 
	if (rc)

		return ERR_PTR(rc);



	rc = devm_cxl_link_parent_dport(host, port, parent_dport);

	if (rc)

		return ERR_PTR(rc);



	return port;



err:
@@ -1164,6 +1191,7 @@ static void delete_endpoint(void *data) 


	device_lock(parent);

	if (parent->driver && !endpoint->dead) {

		devm_release_action(parent, cxl_unlink_parent_dport, endpoint);

		devm_release_action(parent, cxl_unlink_uport, endpoint);

		devm_release_action(parent, unregister_port, endpoint);

	}
@@ -1194,6 +1222,7 @@ EXPORT_SYMBOL_NS_GPL(cxl_endpoint_autoremove, CXL); 
 */

static void delete_switch_port(struct cxl_port *port)

{

	devm_release_action(port->dev.parent, cxl_unlink_parent_dport, port);

	devm_release_action(port->dev.parent, cxl_unlink_uport, port);

	devm_release_action(port->dev.parent, unregister_port, port);

}