linux-kernel - Re: [PATCH v2 1/5] usb: gadget: Add remote wakeup capable flag

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Message-ID: <20230120011513.ajwum224lfwwb6ws@synopsys.com>
Date:   Fri, 20 Jan 2023 01:15:24 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Elson Serrao <quic_eserrao@...cinc.com>
CC:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "balbi@...nel.org" <balbi@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "quic_wcheng@...cinc.com" <quic_wcheng@...cinc.com>,
        "quic_jackp@...cinc.com" <quic_jackp@...cinc.com>
Subject: Re: [PATCH v2 1/5] usb: gadget: Add remote wakeup capable flag

On Thu, Jan 19, 2023, Elson Serrao wrote:
> 
> 
> On 1/18/2023 5:44 PM, Thinh Nguyen wrote:
> > On Tue, Jan 17, 2023, Elson Roy Serrao wrote:
> > > Add a flag to indicate whether the gadget is capable
> > > of sending remote wakeup to the host.
> > > 
> > > Signed-off-by: Elson Roy Serrao <quic_eserrao@...cinc.com>
> > > ---
> > >   drivers/usb/gadget/composite.c | 3 +++
> > >   include/linux/usb/gadget.h     | 2 ++
> > >   2 files changed, 5 insertions(+)
> > > 
> > > diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
> > > index 403563c..b83963a 100644
> > > --- a/drivers/usb/gadget/composite.c
> > > +++ b/drivers/usb/gadget/composite.c
> > > @@ -965,6 +965,9 @@ static int set_config(struct usb_composite_dev *cdev,
> > >   	else
> > >   		usb_gadget_clear_selfpowered(gadget);
> > > +	if (USB_CONFIG_ATT_WAKEUP & c->bmAttributes)
> > > +		gadget->rw_capable = 1;
> > 
> > Some device may not support remote wakeup. gadget->rw_capable should be
> > set and reported by the UDC. May need a gadget ops to enable remote
> > wakeup here.
> > 
> > Thanks,
> > Thinh
> > 
> Not exactly clear on which parameter in UDC decides whether a device
> supports remote wakeup. Here I have this flag just to indicate whether the
> connected device is rw capable based on the bmAttributes populated in the
> config descriptor. If the UDC doesnt have a callback for remote wakeup we
> have that check when calling the gadget op in udc/core.c (have added a
> similar check in usb_func_wakeup() also ).

That flag describes the gadget's capability, not the device
configuration. However, it's being used as a configuration flag.

Thanks,
Thinh

> 
> int usb_gadget_wakeup(struct usb_gadget *gadget)
> {
> 	int ret = 0;
> 
> 	if (!gadget->ops->wakeup) {
> 		ret = -EOPNOTSUPP;
> 		goto out;
> 
> Thanks
> Elson
> 
> > > +
> > >   	usb_gadget_vbus_draw(gadget, power);
> > >   	if (result >= 0 && cdev->delayed_status)
> > >   		result = USB_GADGET_DELAYED_STATUS;
> > > diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
> > > index dc3092c..15785f8 100644
> > > --- a/include/linux/usb/gadget.h
> > > +++ b/include/linux/usb/gadget.h
> > > @@ -385,6 +385,7 @@ struct usb_gadget_ops {
> > >    *	indicates that it supports LPM as per the LPM ECN & errata.
> > >    * @irq: the interrupt number for device controller.
> > >    * @id_number: a unique ID number for ensuring that gadget names are distinct
> > > + * @rw_capable: True if the gadget is capable of sending remote wakeup.
> > >    *