ethtool: provide ring sizes with RINGS_GET request

Implement RINGS_GET request to get ring sizes of a network device. These
are traditionally available via ETHTOOL_GRINGPARAM ioctl request.

Omit attributes for ring types which are not supported by driver or device
(zero reported for maximum).

v2: (all suggested by Jakub Kicinski)
  - minor cleanup in rings_prepare_data()
  - more descriptive rings_reply_size()
  - omit attributes with zero max size

Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 0 deletions

diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index dec82b0b80bd..0dc25a490450 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -217,6 +217,7 @@ ethnl_default_requests[__ETHTOOL_MSG_USER_CNT] = {
 	[ETHTOOL_MSG_WOL_GET]		= &ethnl_wol_request_ops,
 	[ETHTOOL_MSG_FEATURES_GET]	= &ethnl_features_request_ops,
 	[ETHTOOL_MSG_PRIVFLAGS_GET]	= &ethnl_privflags_request_ops,
+	[ETHTOOL_MSG_RINGS_GET]		= &ethnl_rings_request_ops,
 };
 
 static struct ethnl_dump_ctx *ethnl_dump_context(struct netlink_callback *cb)
@@ -748,6 +749,13 @@ static const struct genl_ops ethtool_genl_ops[] = {
 		.flags	= GENL_UNS_ADMIN_PERM,
 		.doit	= ethnl_set_privflags,
 	},
+	{
+		.cmd	= ETHTOOL_MSG_RINGS_GET,
+		.doit	= ethnl_default_doit,
+		.start	= ethnl_default_start,
+		.dumpit	= ethnl_default_dumpit,
+		.done	= ethnl_default_done,
+	},
 };
 
 static const struct genl_multicast_group ethtool_nl_mcgrps[] = {