> 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[];
Dumb C question. What are the padding rules for a union, compared to
base types? Do we know for sure the compiler is not going pad this
structure differently because of the union?
It is however nicely constructed. The 12 __u8 making 3 32bit words, so
we have a total of 12 32bit words, or 6 64bit words, before the
link_mode_masks[], so i don't think padding is technically an issue,
but it would be nice to know the C standard guarantees this.
Andrew
