Re: [PATCH 2/8] virtio-usb: add host role (USB Host Controller) support

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

On Thu, Sep 24, 2026 at 06:09:01PM +0200, Igor Skalkin wrote:
> From: Aiswarya Cyriac <aiswarya.cyriac@oss.qualcomm.com>
> 
> Add the common virtqueue handling code (command, event and data
> queues) shared by every role, and the virtio-usb host controller
> (HCD) implementation, wiring it up as the host role of the dual-role
> driver on top of that common code.
> 
> Each host-role virtual port gets its own HS+SS usb_hcd pair and its
> own root hub (struct virtio_usb_hc_vp), with a fixed
> VIRTIO_USB_VP_MAX_PORTS (8) leaf slots pre-allocated at VP init time
> and reused across connect/disconnect - never dynamically alloc'd or
> freed. This lets the backend forward more than one physical socket -
> and, for host ports behind a physical hub, more than one leaf device
> per socket - as independent virtual ports from the start, instead of
> collapsing everything onto a single shared root hub and having to
> revisit that decision once more than one host-role port needs to
> exist at the same time.
> 
> virtio_usb_add_hcd() derives each VP's HCD bus_name from the parent
> virtio_device with devm_kasprintf() rather than a stack buffer, since
> usb_create_hcd()/usb_create_shared_hcd() store that pointer as-is in
> hcd->self.bus_name without copying it - it must outlive the HCD
> itself.
> 
> Every port is host-role for now, since no other role exists yet;
> vports[].role is populated unconditionally until later commits add
> device role and OTG-based role resolution.
> 
> Signed-off-by: Aiswarya Cyriac <aiswarya.cyriac@oss.qualcomm.com>
> Co-developed-by: Anton Yakovlev <anton.yakovlev@oss.qualcomm.com>
> Signed-off-by: Anton Yakovlev <anton.yakovlev@oss.qualcomm.com>
> Signed-off-by: Vasilii Ianikeev <vasilii.ianikeev@oss.qualcomm.com>
> Co-developed-by: Igor Skalkin <igor.skalkin@oss.qualcomm.com>
> Signed-off-by: Igor Skalkin <igor.skalkin@oss.qualcomm.com>
> ---
>  drivers/usb/virtio_usb/Makefile     |    4 
>  drivers/usb/virtio_usb/controller.c |  105 ++
>  drivers/usb/virtio_usb/controller.h |   35 
>  drivers/usb/virtio_usb/host.c       | 1335 ++++++++++++++++++++++++++++++++++++
>  drivers/usb/virtio_usb/host.h       |  203 +++++
>  drivers/usb/virtio_usb/vq_common.c  |  740 +++++++++++++++++++
>  drivers/usb/virtio_usb/vq_common.h  |  163 ++++
>  include/uapi/linux/virtio_usb.h     |   16 
>  8 files changed, 2585 insertions(+), 16 deletions(-)
>  create mode 100644 drivers/usb/virtio_usb/host.c
>  create mode 100644 drivers/usb/virtio_usb/host.h
>  create mode 100644 drivers/usb/virtio_usb/vq_common.c
>  create mode 100644 drivers/usb/virtio_usb/vq_common.h
> 
> diff --git a/drivers/usb/virtio_usb/controller.c b/drivers/usb/virtio_usb/controller.c
> index 2fc6f50..216edfc 100644
> --- a/drivers/usb/virtio_usb/controller.c
> +++ b/drivers/usb/virtio_usb/controller.c
> @@ -6,9 +6,16 @@
>   */
>  
>  #include <linux/module.h>
> +#include <linux/moduleparam.h>
>  #include <uapi/linux/virtio_ids.h>
>  
>  #include "controller.h"
> +#include "host.h"
> +#include "vq_common.h"
> +
> +u32 virtio_usb_cmd_timeout_ms = MSEC_PER_SEC;
> +module_param_named(cmd_timeout_ms, virtio_usb_cmd_timeout_ms, uint, 0644);
> +MODULE_PARM_DESC(cmd_timeout_ms, "Command completion timeout in milliseconds");

This is not the 1990's, please do not add new module parameters.  Just
make it work without manual configuration at module load time.

If you really need a configuration option, make it per-device and use
the correct, modern, apis for it.

thanks,

greg k-h