UAPI: ethtool: Use __struct_group() in struct ethtool_link_settings

Use the `__struct_group()` helper to create a new tagged
`struct ethtool_link_settings_hdr`. This structure groups together
all the members of the flexible `struct ethtool_link_settings`
except the flexible array. As a result, the array is effectively
separated from the rest of the members without modifying the memory
layout of the flexible structure.

This new tagged struct will be used to fix problematic declarations
of middle-flex-arrays in composite structs[1].

[1] https://git.kernel.org/linus/d88cabfd9abc

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://patch.msgid.link/9e9fb0bd72e5ba1e916acbb4995b1e358b86a689.1730238285.git.gustavoars@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/uapi/linux/ethtool.h b/include/uapi/linux/ethtool.h
index c405ed63acfa27ac879df8023111e3e3602abf49..fc1f54b065f9dad7458c2b89aae3704cfb20ad78 100644 (file)
--- a/include/uapi/linux/ethtool.h
+++ b/include/uapi/linux/ethtool.h
@@ -2511,21 +2511,24 @@ enum ethtool_reset_flags {
  *     autonegotiation; 0 if unknown or not applicable.  Read-only.
  */
 struct ethtool_link_settings {
-       __u32   cmd;
-       __u32   speed;
-       __u8    duplex;
-       __u8    port;
-       __u8    phy_address;
-       __u8    autoneg;
-       __u8    mdio_support;
-       __u8    eth_tp_mdix;
-       __u8    eth_tp_mdix_ctrl;
-       __s8    link_mode_masks_nwords;
-       __u8    transceiver;
-       __u8    master_slave_cfg;
-       __u8    master_slave_state;
-       __u8    rate_matching;
-       __u32   reserved[7];
+       /* New members MUST be added within the __struct_group() macro below. */
+       __struct_group(ethtool_link_settings_hdr, hdr, /* no attrs */,
+               __u32   cmd;
+               __u32   speed;
+               __u8    duplex;
+               __u8    port;
+               __u8    phy_address;
+               __u8    autoneg;
+               __u8    mdio_support;
+               __u8    eth_tp_mdix;
+               __u8    eth_tp_mdix_ctrl;
+               __s8    link_mode_masks_nwords;
+               __u8    transceiver;
+               __u8    master_slave_cfg;
+               __u8    master_slave_state;
+               __u8    rate_matching;
+               __u32   reserved[7];
+       );
        __u32   link_mode_masks[];
        /* layout of link_mode_masks fields:
         * __u32 map_supported[link_mode_masks_nwords];