Re: [RFC PATCH 06/14] usb: core: hcd: Introduce USB HCD APIs for interrupter management

[Wesley Cheng]

Hi Alan,

On 12/24/2022 7:29 AM, Alan Stern wrote:
> On Fri, Dec 23, 2022 at 03:31:52PM -0800, Wesley Cheng wrote:
> > For USB HCDs that can support multiple USB interrupters, expose functions
> > that class drivers can utilize for setting up secondary interrupters.
> > Class drivers can pass this information to its respective clients, i.e.
> > a dedicated DSP.
> >
> > Signed-off-by: Wesley Cheng <quic_wcheng@xxxxxxxxxxx>
> > ---
> >   drivers/usb/core/hcd.c  | 86 +++++++++++++++++++++++++++++++++++++++++
> >   include/linux/usb.h     |  7 ++++
> >   include/linux/usb/hcd.h | 16 +++++++-
> >   3 files changed, 108 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
> > index 8300baedafd2..90ead90faf1d 100644
> > --- a/drivers/usb/core/hcd.c
> > +++ b/drivers/usb/core/hcd.c
>
> > +/**
> > + * usb_hcd_stop_endpoint - Halt USB EP transfers
> > + * @udev: usb device
> > + * @ep: usb ep to stop
> > + *
> > + * Stop pending transfers on a specific USB endpoint.
> > + **/
> > +int usb_hcd_stop_endpoint(struct usb_device *udev,
> > +					struct usb_host_endpoint *ep)
> > +{
> > +	struct usb_hcd *hcd = bus_to_hcd(udev->bus);
> > +	int ret = 0;
> > +
> > +	if (hcd->driver->stop_endpoint)
> > +		ret = hcd->driver->stop_endpoint(hcd, udev, ep);
> > +
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(usb_hcd_stop_endpoint);
>
> You know, there already is a function that does this.  It's named
> usb_hcd_flush_endpoint().  No need to add another function that does the
> same thing.

Thanks for the suggestion and review.

Hmmm...maybe I should change the name of the API then to avoid the 
confusion.  Yes, usb_hcd_flush_endpoint() does ensure that URBs 
submitted to the EP are stopped.  However, with this offloading concept, 
we aren't actually submitting URBs from the main processor, so the 
ep->urb_list will be empty.

This means the usb_hcd_flush_endpoint() API won't actually do anything. 
 What we need is to ensure that we send a XHCI stop ep command to the 
controller.

Thanks
Wesley Cheng