ethtool: provide channel counts with CHANNELS_GET request

Implement CHANNELS_GET request to get channel counts of a network device.
These are traditionally available via ETHTOOL_GCHANNELS ioctl request.

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

v2: (all suggested by Jakub Kicinski)
  - minor cleanup in channels_prepare_data()
  - more descriptive channels_reply_size()
  - omit attributes with zero max count

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 653e009216cd..ac35513abeed 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -218,6 +218,7 @@ ethnl_default_requests[__ETHTOOL_MSG_USER_CNT] = {
 	[ETHTOOL_MSG_FEATURES_GET]	= &ethnl_features_request_ops,
 	[ETHTOOL_MSG_PRIVFLAGS_GET]	= &ethnl_privflags_request_ops,
 	[ETHTOOL_MSG_RINGS_GET]		= &ethnl_rings_request_ops,
+	[ETHTOOL_MSG_CHANNELS_GET]	= &ethnl_channels_request_ops,
 };
 
 static struct ethnl_dump_ctx *ethnl_dump_context(struct netlink_callback *cb)
@@ -763,6 +764,13 @@ static const struct genl_ops ethtool_genl_ops[] = {
 		.flags	= GENL_UNS_ADMIN_PERM,
 		.doit	= ethnl_set_rings,
 	},
+	{
+		.cmd	= ETHTOOL_MSG_CHANNELS_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[] = {