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

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Message-ID:
 <PN3PR01MB95970134B40651A901F825DCB8D72@PN3PR01MB9597.INDPRD01.PROD.OUTLOOK.COM>
Date: Sun, 9 Mar 2025 09:05:45 +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 2:25 PM, gregkh@...uxfoundation.org wrote:
> 
> On Sun, Mar 09, 2025 at 09:52:38AM +0100, 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?
>> 
>>> 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?
>> 
>> And what other drivers use this controller, just normal Linux drivers,
>> or vendor-specific ones?
>> 
>>> Audio - a driver for the T2 audio interface, currently only audio
>>> output is supported.
>> 
>> Again, is this a platform device or does it sit on the BCE "bus" you
>> will create here?
> 
> Also, it looks like you are creating some new user/kernel apis here
> (i.e. a char device for a USB host controller?)  So those need to be
> explained a lot as to what they are for and who is using them as I
> really don't understand their need, nor know what userspace code
> controls them.

I'll cleanup the code, and try to fix the todos if possible, and send a patch with proper explanation. My main purpose to put it in staging was that without keyboard, trackpad and other input devices, linux is unusable on t2 macs.

> 
> thanks,
> 
> greg k-h