Commits
Matan Barak committed b4ff3a36d3e
net/mlx5: Use offset based reserved field names in the IFC header file
mlx5_ifc.h is a header file representing the API and ABI between
the driver to the firmware and hardware. This file is used from
both the mlx5_ib and mlx5_core drivers.
Previously, this file used incrementing counter to indicate
reserved fields, for example:
struct mlx5_ifc_odp_per_transport_service_cap_bits {
u8 send[0x1];
u8 receive[0x1];
u8 write[0x1];
u8 read[0x1];
u8 reserved_0[0x1];
u8 srq_receive[0x1];
u8 reserved_1[0x1a];
};
If one developer implements through net-next feature A that uses
reserved_0, they replace it with featureA and renames reserved_1 to
reserved_0. In the same kernel cycle, a 2nd developer could implement
feature B through the rdma tree, that uses reserved_1 and split it to
featureB and a smaller reserved_1 field. This will cause a conflict
when the two trees are merged.
The source of this conflict is that the 1st developer changed *all*
reserved fields.
As Linus suggested, we change the layout of structs to:
struct mlx5_ifc_odp_per_transport_service_cap_bits {
u8 send[0x1];
u8 receive[0x1];
u8 write[0x1];
u8 read[0x1];
u8 reserved_at_4[0x1];
u8 srq_receive[0x1];
u8 reserved_at_6[0x1a];
};
This makes the conflicts much more rare and preserves the locality of
changes.
Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Alaa Hleihel <alaa@mellanox.com>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>