devlink: extend health reporter dump selector by port index

Introduce a possibility for devlink object to expose attributes it
supports for selection of dumped objects.

Use this by health reporter to indicate it supports port index based
selection of dump objects. Implement this selection mechanism in
devlink_nl_cmd_health_reporter_get_dump_one()

Example:
$ devlink health
pci/0000:08:00.0:
  reporter fw
    state healthy error 0 recover 0 auto_dump true
  reporter fw_fatal
    state healthy error 0 recover 0 grace_period 60000 auto_recover true auto_dump true
  reporter vnic
    state healthy error 0 recover 0
pci/0000:08:00.0/32768:
  reporter vnic
    state healthy error 0 recover 0
pci/0000:08:00.0/32769:
  reporter vnic
    state healthy error 0 recover 0
pci/0000:08:00.0/32770:
  reporter vnic
    state healthy error 0 recover 0
pci/0000:08:00.1:
  reporter fw
    state healthy error 0 recover 0 auto_dump true
  reporter fw_fatal
    state healthy error 0 recover 0 grace_period 60000 auto_recover true auto_dump true
  reporter vnic
    state healthy error 0 recover 0
pci/0000:08:00.1/98304:
  reporter vnic
    state healthy error 0 recover 0
pci/0000:08:00.1/98305:
  reporter vnic
    state healthy error 0 recover 0
pci/0000:08:00.1/98306:
  reporter vnic
    state healthy error 0 recover 0

$ devlink health show pci/0000:08:00.0
pci/0000:08:00.0:
  reporter fw
    state healthy error 0 recover 0 auto_dump true
  reporter fw_fatal
    state healthy error 0 recover 0 grace_period 60000 auto_recover true auto_dump true
  reporter vnic
    state healthy error 0 recover 0
pci/0000:08:00.0/32768:
  reporter vnic
    state healthy error 0 recover 0
pci/0000:08:00.0/32769:
  reporter vnic
    state healthy error 0 recover 0
pci/0000:08:00.0/32770:
  reporter vnic
    state healthy error 0 recover 0

$ devlink health show pci/0000:08:00.0/32768
pci/0000:08:00.0/32768:
  reporter vnic
    state healthy error 0 recover 0

The last command is possible because of this patch.
Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20230811155714.1736405-13-jiri@resnulli.usSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/devlink/health.c

@@ -390,12 +390,23 @@ static int devlink_nl_health_reporter_get_dump_one(struct sk_buff *msg,
 						   int flags)
 {
 	struct devlink_nl_dump_state *state = devlink_dump_state(cb);
+	const struct genl_dumpit_info *info = genl_dumpit_info(cb);
 	struct devlink_health_reporter *reporter;
+	unsigned long port_index_end = ULONG_MAX;
+	struct nlattr **attrs = info->attrs;
+	unsigned long port_index_start = 0;
 	struct devlink_port *port;
 	unsigned long port_index;
 	int idx = 0;
 	int err;
 
+	if (attrs && attrs[DEVLINK_ATTR_PORT_INDEX]) {
+		port_index_start = nla_get_u32(attrs[DEVLINK_ATTR_PORT_INDEX]);
+		port_index_end = port_index_start;
+		flags |= NLM_F_DUMP_FILTERED;
+		goto per_port_dump;
+	}
+
 	list_for_each_entry(reporter, &devlink->reporter_list, list) {
 		if (idx < state->idx) {
 			idx++;
@@ -412,7 +423,9 @@ static int devlink_nl_health_reporter_get_dump_one(struct sk_buff *msg,
 		}
 		idx++;
 	}
-	xa_for_each(&devlink->ports, port_index, port) {
+per_port_dump:
+	xa_for_each_range(&devlink->ports, port_index, port,
+			  port_index_start, port_index_end) {
 		list_for_each_entry(reporter, &port->reporter_list, list) {
 			if (idx < state->idx) {
 				idx++;