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

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Date:   Fri, 20 Jan 2023 16:06:36 -0800
From:   Elson Serrao <quic_eserrao@...cinc.com>
To:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>
CC:     "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 1/19/2023 5:15 PM, Thinh Nguyen wrote:
> 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
> 

Thank you for the clarification. Please let me know if below approach 
where we consider both gadget's capability and device configuration fine?

if (gadget->ops->wakeup || gadget->ops->func_wakeup)
    gadget->rw_capable = USB_CONFIG_ATT_WAKEUP & c->bmAttributes ? 1: 0;

Thanks
Elson
>>
>> 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.
>>>>     *