From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Lunn <andrew@lunn.ch>
Subject: Re: [PATCH net-next 0/9] devlink: Add support for region access
Date: Thu, 29 Mar 2018 21:51:54 +0200
Message-ID: <20180329195154.GB15565@lunn.ch>
References: <1522339672-18273-1-git-send-email-valex@mellanox.com>
 <20180329171359.GA12150@lunn.ch>
 <962b56c1-d471-97ec-e8e9-18252e809dfe@mellanox.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: "David S. Miller" <davem@davemloft.net>, netdev@vger.kernel.org,
        Tariq Toukan <tariqt@mellanox.com>,
        Jiri Pirko <jiri@mellanox.com>
To: Alex Vesker <valex@mellanox.com>
Return-path: <netdev-owner@vger.kernel.org>
Received: from vps0.lunn.ch ([185.16.172.187]:46666 "EHLO vps0.lunn.ch"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1751082AbeC2Tv7 (ORCPT <rfc822;netdev@vger.kernel.org>);
        Thu, 29 Mar 2018 15:51:59 -0400
Content-Disposition: inline
In-Reply-To: <962b56c1-d471-97ec-e8e9-18252e809dfe@mellanox.com>
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

> >>Show all of the exposed regions with region sizes:
> >>$ devlink region show
> >>pci/0000:00:05.0/cr-space: size 1048576 snapshot [1 2]
> >So you have 2Mbytes of snapshot data. Is this held in the device, or
> >kernel memory?
> This is allocated in devlink, the maximum number of snapshots is set by the
> driver.

And it seems to want contiguous pages. How well does that work after
the system has been running for a while and memory is fragmented?

> >>Dump a snapshot:
> >>$ devlink region dump pci/0000:00:05.0/fw-health snapshot 1
> >>0000000000000000 0014 95dc 0014 9514 0035 1670 0034 db30
> >>0000000000000010 0000 0000 ffff ff04 0029 8c00 0028 8cc8
> >>0000000000000020 0016 0bb8 0016 1720 0000 0000 c00f 3ffc
> >>0000000000000030 bada cce5 bada cce5 bada cce5 bada cce5
> >>
> >>Read a specific part of a snapshot:
> >>$ devlink region read pci/0000:00:05.0/fw-health snapshot 1 address 0
> >>	length 16
> >>0000000000000000 0014 95dc 0014 9514 0035 1670 0034 db30
> >Why a separate command? It seems to be just a subset of dump.
> 
> This is useful when debugging values on specific addresses, this also
> brings the API one step closer for a read and write API.

The functionality is useful, yes. But why two commands? Why not one
command, dump, which takes optional parameters?

Also, i doubt write support will be accepted. That sounds like the
start of an API to allow a user space driver.

      Andrew