Re: [PATCH 0/8] virtio-usb: add dual-role virtio USB driver

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, Sep 24, 2026 at 06:08:59PM +0200, Igor Skalkin wrote:
> This series adds a new virtio-usb driver: a dual-role virtio device
> capable of acting as a USB host controller, a USB device controller,
> or both simultaneously with runtime role switching between the two
> (USB OTG-style role switching) on ports that support it.
> 
> The corresponding virtio-usb device specification has been posted to
> virtio-comment for review. This series matches the v2 revision of
> that spec, which reconciles a small number of protocol details
> (per-role virtqueue presentation, host-role vp_idx for hub/multi-VP
> support, and the device-role BIND/UNBIND event split) that were
> clarified while integrating and testing this driver against the
> spec:

Why do we need this at all when we have other ways of doing usb devices
through virtio?

Why is a USB virtio spec needed at all, who is going to use it?


> 
>   [RFC PATCH v2] virtio-usb: Add initial virtio-usb specification
>   Igor Skalkin <igor.skalkin@oss.qualcomm.com>
>   virtio-comment@lists.linux.dev
>   https://lore.kernel.org/virtio-comment/20260924154007.143927-1-igor.skalkin@oss.qualcomm.com/
> 
> This driver has been tested end-to-end against our own userspace
> virtio-usb device implementation (host-side backend) in two setups:

Where is that code and why isn't it part of this submission?

>   4-5: USB OTG-style role query and role-switching support.

There's a reason OTG isn't used anymore by devices, how have you
addressed those problems here?  And why duplicate the failures of the
past?

>   6:   endpoint-lifecycle robustness rework (async split-phase state
>        machine, replacing an earlier out-of-tree gadget.nonatomic
>        patch that didn't pass upstream review).
>   7:   SuperSpeed device-role support.

Why should speed settings matter to a virtual connection?

thanks,

greg k-h