linux-kernel - Re: [RFC 0/2] of: Add whitelist

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Date:   Thu, 30 Nov 2017 07:18:09 -0500
From:   Frank Rowand <frowand.list@...il.com>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     Alan Tull <atull@...nel.org>,
        Pantelis Antoniou <pantelis.antoniou@...sulko.com>,
        Moritz Fischer <mdf@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-fpga@...r.kernel.org
Subject: Re: [RFC 0/2] of: Add whitelist

On 11/29/17 08:31, Rob Herring wrote:
> On Wed, Nov 29, 2017 at 3:20 AM, Frank Rowand <frowand.list@...il.com> wrote:
>> On 11/27/17 15:58, Alan Tull wrote:
>>> Here's a proposal for a whitelist to lock down the dynamic device tree.
>>>
>>> For an overlay to be accepted, all of its targets are required to be
>>> on a target node whitelist.
>>>
>>> Currently the only way I have to get on the whitelist is calling a
>>> function to add a node.  That works for fpga regions, but I think
>>> other uses will need a way of having adding specific nodes from the
>>> base device tree, such as by adding a property like 'allow-overlay;'
>>> or 'allow-overlay = "okay";' If that is acceptable, I could use some
>>> advice on where that particular code should go.
>>>
>>> Alan
>>>
>>> Alan Tull (2):
>>>   of: overlay: add whitelist
>>>   fpga: of region: add of-fpga-region to whitelist
>>>
>>>  drivers/fpga/of-fpga-region.c |  9 ++++++
>>>  drivers/of/overlay.c          | 73 +++++++++++++++++++++++++++++++++++++++++++
>>>  include/linux/of.h            | 12 +++++++
>>>  3 files changed, 94 insertions(+)
>>>
>>
>> The plan was to use connectors to restrict where an overlay could be applied.
>> I would prefer not to have multiple methods for accomplishing the same thing
>> unless there is a compelling reason to do so.
> 
> Connector nodes need a mechanism to enable themselves, too. I don't
> think connector nodes are going to solve every usecase.
> 
> Rob
> 

The overlay code related to connectors does not exist yet, so my comment
is going to be theoretical.

I would expect the overlay code to check that the target of the overlay
fragment is a connector node, so there is no need to explicitly "enable"
applying an overlay to a connector node.

-Frank