[PATCH 2/6] usb: xhci: Set up endpoints for the first 2 interfaces

[Janne Grunau]

Hej,

On Sun, Feb 25, 2024, at 22:47, Marek Vasut wrote:
> On 2/25/24 4:28 PM, Janne Grunau wrote:
>> 
>> 
>> On Wed, Feb 21, 2024, at 13:39, Marek Vasut wrote:
>>> On 2/21/24 08:25, Janne Grunau via B4 Relay wrote:
>>>> From: Janne Grunau <j at jannau.net>
>>>>
>>>> Apple USB keyboards carry the HID keyboard boot protocol on the second
>>>> interface. Using the second interface in the USB keyboard driver does
>>>> not work since the xhci has not allocated a transfer ring.
>>>
>>> So, what does this patch do ? That is not clear from the commit message.
>> 
>> rewritten for v2:
>> | usb: xhci: Set up endpoints for the first 2 interfaces
>> |
>> | The xhci driver currently only does the necessary initialization for
>> | endpoints found in the first interface descriptor. Apple USB keyboards
>> | (released 2021) use the second interface descriptor for the HID keyboard
>> | boot protocol. To allow USB drivers to use endpoints from other
>> | interface descriptors the xhci driver needs to ensure these endpoints
>> | are initialized as well.
>> | Use USB_MAX_ACTIVE_INTERFACES to control how many interface descriptors
>> | are initialized and useable. Currently defined to 2 as that is enough to
>> | make the Apple keyboard usable.
>
> Would it make sense to make this a tunable Kconfig option ?

I thought about that but I don't think it's worth it. We would have to default it to 2 (at least when the USB keyboard driver is enabled) since we can't predict which devices will be connected.
Why would anyone chose a different value than the fixed value? I can't think of convincing reasons.

Janne