linux-kernel - Re: [PATCH 4/6] usb: gadget: add functions to signal udc driver to delay status stage

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Date:   Thu, 18 Oct 2018 07:46:14 -0500
From:   Bin Liu <b-liu@...com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
CC:     Paul Elder <paul.elder@...asonboard.com>,
        <kieran.bingham@...asonboard.com>, <gregkh@...uxfoundation.org>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <balbi@...nel.org>, <stern@...land.harvard.edu>, <rogerq@...com>
Subject: Re: [PATCH 4/6] usb: gadget: add functions to signal udc driver to
 delay status stage

Laurent,

On Thu, Oct 18, 2018 at 02:45:32AM +0300, Laurent Pinchart wrote:
> Hi Bin,
> 
> On Thursday, 11 October 2018 19:10:21 EEST Bin Liu wrote:
> > On Tue, Oct 09, 2018 at 10:49:01PM -0400, Paul Elder wrote:
> > > A usb gadget function driver may or may not want to delay the status
> > > stage of a control OUT request. An instance it might want to is to
> > > asynchronously validate the data of a class-specific request.
> > > 
> > > Add a function usb_ep_delay_status to allow function drivers to choose
> > > to delay the status stage in the request completion handler. The UDC
> > > should then check the usb_ep->delayed_status flag and act accordingly to
> > > delay the status stage.
> > > 
> > > Also add a function usb_ep_send_response as a wrapper for
> > > usb_ep->ops->send_response, whose prototype is added as well. This
> > > function should be called by function drivers to tell the UDC what to
> > > reply in the status stage that it has requested to be delayed.
> > > 
> > > Signed-off-by: Paul Elder <paul.elder@...asonboard.com>
> > > Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> > > ---
> > > 
> > >  drivers/usb/gadget/udc/core.c | 35 +++++++++++++++++++++++++++++++++++
> > >  include/linux/usb/gadget.h    | 11 +++++++++++
> > >  2 files changed, 46 insertions(+)
> > > 
> > > diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
> > > index af88b48c1cea..1ec5ce6b43cd 100644
> > > --- a/drivers/usb/gadget/udc/core.c
> > > +++ b/drivers/usb/gadget/udc/core.c
> > > @@ -443,6 +443,41 @@ void usb_ep_fifo_flush(struct usb_ep *ep)
> > >  }
> > >  EXPORT_SYMBOL_GPL(usb_ep_fifo_flush);
> > > 
> > > +/**
> > > + * usb_ep_ep_delay_status - set delay_status flag
> > > + * @ep: the endpoint whose delay_status flag is being set
> > > + *
> > > + * This function instructs the UDC to delay the status stage of a control
> > > + * request. It can only be called from the request completion handler of
> > > a
> > > + * control request.
> > > + */
> > > +void usb_ep_delay_status(struct usb_ep *ep)
> > > +{
> > > +	ep->delayed_status = true;
> > > +}
> > > +EXPORT_SYMBOL_GPL(usb_ep_delay_status);
> > 
> > Is usb_ep_set_delay_status() better? I thought it implies get/return
> > action if a verb is missing in the function name.
> 
> For what it's worth, I understand the function name as "delay the status 
> stage", with "delay" being a verb. Maybe the short description could be 
> updated accordingly.

Okay, maybe it is just my own understanding problem. I thought about
delay as the verb, but then notice the var is called delayed_status,
then I was thinking delay_status in the function name as the flag.

No worries.

Regards,
-Bin.