netdev - Re: [bug report] net/mlx5e: E-Switch, Maintain vhca_id to vport

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Message-ID: <20210210122801.GW20820@kadam>
Date:   Wed, 10 Feb 2021 15:28:01 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Leon Romanovsky <leon@...nel.org>
Cc:     vladbu@...dia.com, linux-rdma@...r.kernel.org,
        linux-netdev <netdev@...r.kernel.org>
Subject: Re: [bug report] net/mlx5e: E-Switch, Maintain vhca_id to vport_num
 mapping

On Wed, Feb 10, 2021 at 01:48:20PM +0200, Leon Romanovsky wrote:
> On Wed, Feb 10, 2021 at 11:51:51AM +0300, Dan Carpenter wrote:
> > 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.

regards,
dan carpenter