tools: ynl: make yarg the first member of struct ynl_dump_state

All YNL parsing code expects a pointer to struct ynl_parse_arg AKA yarg.
For dump was pass in struct ynl_dump_state, which works fine, because
struct ynl_dump_state and struct ynl_parse_arg have identical layout
for the members that matter.. but it's a bit hacky.
Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Link: https://lore.kernel.org/r/20240227223032.1835527-7-kuba@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

tools/net/ynl/lib/ynl-priv.h

@@ -104,8 +104,7 @@ struct ynl_req_state {
 };
 
 struct ynl_dump_state {
-	struct ynl_sock *ys;
-	struct ynl_policy_nest *rsp_policy;
+	struct ynl_parse_arg yarg;
 	void *first;
 	struct ynl_dump_list_type *last;
 	size_t alloc_sz;

tools/net/ynl/lib/ynl.c

@@ -864,7 +864,7 @@ static int ynl_dump_trampoline(const struct nlmsghdr *nlh, void *data)
 	struct ynl_parse_arg yarg = {};
 	int ret;
 
-	ret = ynl_check_alien(ds->ys, nlh, ds->rsp_cmd);
+	ret = ynl_check_alien(ds->yarg.ys, nlh, ds->rsp_cmd);
 	if (ret)
 		return ret < 0 ? MNL_CB_ERROR : MNL_CB_OK;
 
@@ -878,8 +878,7 @@ static int ynl_dump_trampoline(const struct nlmsghdr *nlh, void *data)
 		ds->last->next = obj;
 	ds->last = obj;
 
-	yarg.ys = ds->ys;
-	yarg.rsp_policy = ds->rsp_policy;
+	yarg = ds->yarg;
 	yarg.data = &obj->data;
 
 	return ds->cb(nlh, &yarg);

tools/net/ynl/ynl-gen-c.py

@@ -1844,14 +1844,15 @@ def print_dump(ri):
 
     ri.cw.write_func_lvar(local_vars)
 
-    ri.cw.p('yds.ys = ys;')
+    ri.cw.p('yds.yarg.ys = ys;')
+    ri.cw.p(f"yds.yarg.rsp_policy = &{ri.struct['reply'].render_name}_nest;")
+    ri.cw.p("yds.yarg.data = NULL;")
     ri.cw.p(f"yds.alloc_sz = sizeof({type_name(ri, rdir(direction))});")
     ri.cw.p(f"yds.cb = {op_prefix(ri, 'reply', deref=True)}_parse;")
     if ri.op.value is not None:
         ri.cw.p(f'yds.rsp_cmd = {ri.op.enum_name};')
     else:
         ri.cw.p(f'yds.rsp_cmd = {ri.op.rsp_value};')
-    ri.cw.p(f"yds.rsp_policy = &{ri.struct['reply'].render_name}_nest;")
     ri.cw.nl()
     ri.cw.p(f"nlh = ynl_gemsg_start_dump(ys, {ri.nl.get_family_id()}, {ri.op.enum_name}, 1);")