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

[Aditya Garg]

> On 9 Mar 2025, at 2:46 PM, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
> 
> On Sun, Mar 09, 2025 at 09:03:29AM +0000, Aditya Garg wrote:
>> 
>> 
>>>> On 9 Mar 2025, at 2:24 PM, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
>>> 
>>> On Sun, Mar 09, 2025 at 08:40:31AM +0000, Aditya Garg wrote:
>>>> From: Paul Pawlowski <paul@xxxxxxxx>
>>>> 
>>>> 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