netdev - Re: [PATCH] net: dsa: mv88e6xxx: Add MV88E6352 DT compatible

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 12 Sep 2018 10:38:41 +0200
From:   Marek Vasut <marex@...x.de>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH] net: dsa: mv88e6xxx: Add MV88E6352 DT compatible

On 09/12/2018 02:46 AM, Andrew Lunn wrote:
> On Wed, Sep 12, 2018 at 02:04:54AM +0200, Marek Vasut wrote:
>> On 09/12/2018 01:32 AM, Andrew Lunn wrote:
>>>> compatible = "marvell,mv88e6352", "marvell,mv88e6085";
>>>
>>> Just "marvell,mv88e6085";
>>>
>>> Please take a look at all the other DT files using the Marvell
>>> chips. You will only ever find "marvell,mv88e6085" or
>>> "marvell,mv88e6190", because everything is compatible to one of these
>>> two.
>>
>> Well, until you find a difference between those chips which you cannot
>> discern based solely on the ID register content. Then it's better to
>> have a compatible to match on which matches the actual chip.
> 
> Hi Marek
> 
> We have been around this loop before. The problem with putting in a
> more specific compatible is that nothing is validating it. So it is
> going to be wrong, simple because people cut/paste, and don't
> necessary change it. So when we do need to look at it, we cannot look
> at it, because it is wrong.
> 
> I would only add a more specific compatible if and when we need it, it
> is actually used, and we can verify it is correct.

You may need it in the future and it may not be possible to adjust the
DT then. So having a specific compatible and fallback compatible is I
think the way to go. You can always match on the fallback and if the
time comes, you can match on the specific one because it's there. In
addition to that, such a DT would fully correctly describe the hardware,
unlike one with only a fallback compatible.

Regarding validation, I don't see other systems using this approach
(specific + fallback compatible) having a problem with validation.
What is the trick there ?

-- 
Best regards,
Marek Vasut