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

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Date:   Thu, 19 Jan 2023 16:13:54 -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 1/18/2023 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 ).

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.
>>    *
>>    * Gadgets have a mostly-portable "gadget driver" implementing device
>>    * functions, handling all usb configurations and interfaces.  Gadget
>> @@ -446,6 +447,7 @@ struct usb_gadget {
>>   	unsigned			lpm_capable:1;
>>   	int				irq;
>>   	int				id_number;
>> +	unsigned			rw_capable:1;
>>   };
>>   #define work_to_gadget(w)	(container_of((w), struct usb_gadget, work))
>>   
>> -- 
>> 2.7.4