On Wed, Feb 10, 2021 at 03:28:01PM +0300, Dan Carpenter wrote:

On Wed, Feb 10, 2021 at 01:48:20PM +0200, Leon Romanovsky wrote:

quoted

On Wed, Feb 10, 2021 at 11:51:51AM +0300, Dan Carpenter wrote:

quoted

Hello Vlad Buslov,

The patch 84ae9c1f29c0: "net/mlx5e: E-Switch, Maintain vhca_id to
vport_num mapping" from Sep 23, 2020, leads to the following static
checker warning:

	drivers/net/ethernet/mellanox/mlx5/core/vport.c:1170 mlx5_vport_get_other_func_cap()
	warn: odd binop '0x0 & 0x1'

drivers/net/ethernet/mellanox/mlx5/core/vport.c
  1168  int mlx5_vport_get_other_func_cap(struct mlx5_core_dev *dev, u16 function_id, void *out)
  1169  {
  1170          u16 opmod = (MLX5_CAP_GENERAL << 1) | (HCA_CAP_OPMOD_GET_MAX & 0x01);

HCA_CAP_OPMOD_GET_MAX is zero.  The 0x01 is a magical number.

  1171          u8 in[MLX5_ST_SZ_BYTES(query_hca_cap_in)] = {};
  1172
  1173          MLX5_SET(query_hca_cap_in, in, opcode, MLX5_CMD_OP_QUERY_HCA_CAP);
  1174          MLX5_SET(query_hca_cap_in, in, op_mod, opmod);
  1175          MLX5_SET(query_hca_cap_in, in, function_id, function_id);
  1176          MLX5_SET(query_hca_cap_in, in, other_function, true);
  1177          return mlx5_cmd_exec_inout(dev, query_hca_cap, in, out);
  1178  }

Dan,

I'm running smatch which is based on 6193b3b71beb ("extra: fix some error pointer handling")
and I don't see this error. Should I run something special?

This check is too crap to publish.

The heuristic was "a bitwise AND which always results in zero" but a lot
of code does stuff like:  "data = 0x00 << 0 | 0x04 << 8 | 0x12 << 16;"
I could never figure out a way to make the check useful enough to
publish.

But you can warn about simple cases like above, which is constant zero
AND something.

Thanks

regards,
dan carpenter