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 19:13:59 +0200
Message-ID: <20180329171359.GA12150@lunn.ch>
References: <1522339672-18273-1-git-send-email-valex@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]:46543 "EHLO vps0.lunn.ch"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1750735AbeC2ROD (ORCPT <rfc822;netdev@vger.kernel.org>);
        Thu, 29 Mar 2018 13:14:03 -0400
Content-Disposition: inline
In-Reply-To: <1522339672-18273-1-git-send-email-valex@mellanox.com>
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

On Thu, Mar 29, 2018 at 07:07:43PM +0300, Alex Vesker wrote:
> This is a proposal which will allow access to driver defined address
> regions using devlink. Each device can create its supported address
> regions and register them. A device which exposes a region will allow
> access to it using devlink.
> 
> The suggested implementation will allow exposing regions to the user,
> reading and dumping snapshots taken from different regions. 
> A snapshot represents a memory image of a region taken by the driver.
> 
> If a device collects a snapshot of an address region it can be later
> exposed using devlink region read or dump commands.
> This functionality allows for future analyses on the snapshots to be
> done.

Hi Alex

So the device is in change of making a snapshot? A user cannot
initiate it?

Seems like if i'm trying to debug something, i want to take a snapshot
in the good state, issue the command which breaks things, and then
take another snapshot. Looking at the diff then gives me an idea what
happened.

> 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?

> 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.

    Andrew