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Date: Tue, 29 May 2018 09:49:22 -0600
From: Jason Gunthorpe <jgg@ziepe.ca>
To: Hans Westgaard Ry <hans.westgaard.ry@oracle.com>
Cc: Doug Ledford <dledford@redhat.com>,
        Hakon Bugge <haakon.bugge@oracle.com>,
        Jack Morgenstein <jackm@dev.mellanox.co.il>,
        Daniel Jurgens <danielj@mellanox.com>,
        Parav Pandit <parav@mellanox.com>,
        Pravin Shedge <pravin.shedge4linux@gmail.com>,
        linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] IB/mad: Use ID allocator routines to allocate agent
 number
Message-ID: <20180529154922.GA18457@ziepe.ca>
References: <20180529073808.27735-1-hans.westgaard.ry@oracle.com>
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On Tue, May 29, 2018 at 09:38:08AM +0200, Hans Westgaard Ry wrote:
> The agent TID is a 64 bit value split in two dwords.  The least
> significant dword is the TID running counter. The most significant
> dword is the agent number. In the CX-3 shared port model, the mlx4
> driver uses the most significant byte of the agent number to store the
> slave number, making agent numbers greater and equal to 2^24 (3 bytes)
> unusable.

There is no reason for this to be an ida, just do something like

 mad_agent_priv->agent.hi_tid = atomic_inc_return(&ib_mad_client_id) & mad_agent_priv->ib_dev->tid_mask;

And have the driver set tid_mask to 3 bytes of 0xFF

And no sysctl.

Jason