linux-kernel - Re: [PATCH RFC] staging: Add driver to communicate with the T2 Security Chip

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Message-ID:
 <PN3PR01MB9597F037471B133B54BA25BCB8D72@PN3PR01MB9597.INDPRD01.PROD.OUTLOOK.COM>
Date: Sun, 9 Mar 2025 09:28:01 +0000
From: Aditya Garg <gargaditya08@...e.com>
To: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC: "bhelgaas@...gle.com" <bhelgaas@...gle.com>, "joro@...tes.org"
	<joro@...tes.org>, "will@...nel.org" <will@...nel.org>,
	"robin.murphy@....com" <robin.murphy@....com>,
	"andriy.shevchenko@...ux.intel.com" <andriy.shevchenko@...ux.intel.com>,
	"linux-staging@...ts.linux.dev" <linux-staging@...ts.linux.dev>, Linux Kernel
 Mailing List <linux-kernel@...r.kernel.org>, "linux-pci@...r.kernel.org"
	<linux-pci@...r.kernel.org>, "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
	Aun-Ali Zaidi <admin@...eit.net>, "paul@...rm.io" <paul@...rm.io>, Orlando
 Chamberlain <orlandoch.dev@...il.com>
Subject: Re: [PATCH RFC] staging: Add driver to communicate with the T2
 Security Chip



> On 9 Mar 2025, at 2:46 PM, gregkh@...uxfoundation.org wrote:
> 
> On Sun, Mar 09, 2025 at 09:03:29AM +0000, Aditya Garg wrote:
>> 
>> 
>>>> On 9 Mar 2025, at 2:24 PM, gregkh@...uxfoundation.org wrote:
>>> 
>>> On Sun, Mar 09, 2025 at 08:40:31AM +0000, Aditya Garg wrote:
>>>> From: Paul Pawlowski <paul@...rm.io>
>>>> 
>>>> This patch adds a driver named apple-bce, to add support for the T2
>>>> Security Chip found on certain Macs.
>>>> 
>>>> The driver has 3 main components:
>>>> 
>>>> BCE (Buffer Copy Engine) - this is what the files in the root directory
>>>> are for. This estabilishes a basic communication channel with the T2.
>>>> VHCI and Audio both require this component.
>>> 
>>> So this is a new "bus" type?  Or a platform resource?  Or something
>>> else?
>> 
>> It's a PCI device
> 
> Great, but then is the resources split up into smaller drivers that then
> bind to it?  How does the other devices talk to this?

We technically can split up these 3 into separate drivers and put then into their own trees.
> 
>>>> VHCI - this is a virtual USB host controller; keyboard, mouse and
>>>> other system components are provided by this component (other
>>>> drivers use this host controller to provide more functionality).
>>> 
>>> I don't understand, why does a security chip have a USB virtual
>>> interface in it?  What "devices" hang off of it that are found and
>>> enumerated by the host OS?
>> 
>> The t2 chip not only handles security, but also has a usb hub, which connects the internal keyboard, trackpad, touchbar, webcam, and other internal devices. The external usb ports are separate.
> 
> That feels strange, but hey, we've seen worse :)
> 
> thanks,
> 
> greg k-h