linux-kernel - RE: [RFC PATCH 17/22] thunderbolt: Add initial support for USB4

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Message-ID: <767f2f97059e4e9f861080672aaa18d3@AUSX13MPC105.AMER.DELL.COM>
Date:   Wed, 2 Oct 2019 15:09:46 +0000
From:   <Mario.Limonciello@...l.com>
To:     <mika.westerberg@...ux.intel.com>
CC:     <linux-usb@...r.kernel.org>, <andreas.noever@...il.com>,
        <michael.jamet@...el.com>, <YehezkelShB@...il.com>,
        <rajmohan.mani@...el.com>,
        <nicholas.johnson-opensource@...look.com.au>, <lukas@...ner.de>,
        <gregkh@...uxfoundation.org>, <stern@...land.harvard.edu>,
        <anthony.wong@...onical.com>, <linux-kernel@...r.kernel.org>
Subject: RE: [RFC PATCH 17/22] thunderbolt: Add initial support for USB4

> -----Original Message-----
> From: Mika Westerberg <mika.westerberg@...ux.intel.com>
> Sent: Wednesday, October 2, 2019 3:39 AM
> To: Limonciello, Mario
> Cc: linux-usb@...r.kernel.org; andreas.noever@...il.com;
> michael.jamet@...el.com; YehezkelShB@...il.com; rajmohan.mani@...el.com;
> nicholas.johnson-opensource@...look.com.au; lukas@...ner.de;
> gregkh@...uxfoundation.org; stern@...land.harvard.edu;
> anthony.wong@...onical.com; linux-kernel@...r.kernel.org
> Subject: Re: [RFC PATCH 17/22] thunderbolt: Add initial support for USB4
> 
> 
> [EXTERNAL EMAIL]
> 
> On Tue, Oct 01, 2019 at 06:14:23PM +0000, Mario.Limonciello@...l.com wrote:
> > One more thought; would you consider exporting to sysfs sw-
> >config.vendor_id?
> > Maybe an attribute that is switch_vendor?
> >
> > Userland fwupd also does validation on the NVM and will need to follow this.
> > The same check will go into fwupd to match the vendor and lack of
> nvm_non_active0
> > to mark the device as not updatable.  When the checks in the kernel get
> relaxed,
> > some NVM parsing will have to make it over to fwupd too to relax the check at
> that point.
> 
> The original idea was that the kernel does the basic validation and
> userspace then does more complex checks. Currently you can compare the
> two NVM images (active one and the new) and find that information there.
> I think fwupd is doing just that already. Is that not enough?

I guess for fwupd we can do this without the extra attribute:

1) If no NVM files or nvm_version: means unsupported vendor -show that messaging somewhere.
This means kernel doesn't know the vendor.

2) If NVM file and nvm_version: means kernel knows it
*fwupd checks the vendor offset for intel.
-> intel: good, proceed
->something else: fwupd needs to learn the format for the new vendor, show messaging

There is the unlikely case that kernel knows new vendor format and vendor NVM happened to have
same value as Intel vendor ID in same location of Intel NVM but another meaning.
Hopefully that doesn't happen :)