linux-kernel - Re: [PATCH v1 2/3] usb: gadget: Use get_status callback to set remote wakeup capability

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Message-ID: <4d68cb04-377f-4ebf-99c7-c63b68aebf60@oss.qualcomm.com>
Date: Tue, 8 Apr 2025 10:36:58 +0530
From: Prashanth K <prashanth.k@....qualcomm.com>
To: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kees Bakker <kees@...erbout.nl>,
        William McVicker <willmcvicker@...gle.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...nel.org" <stable@...nel.org>
Subject: Re: [PATCH v1 2/3] usb: gadget: Use get_status callback to set remote
 wakeup capability



On 08-04-25 06:48 am, Thinh Nguyen wrote:
> On Thu, Apr 03, 2025, Prashanth K wrote:
>> Currently when the host sends GET_STATUS request for an interface,
>> we use get_status callbacks to set/clear remote wakeup capability
>> of that interface. And if get_status callback isn't present for
>> that interface, then we assume its remote wakeup capability based
>> on bmAttributes.
>>
>> Now consider a scenario, where we have a USB configuration with
>> multiple interfaces (say ECM + ADB), here ECM is remote wakeup
>> capable and as of now ADB isn't. And bmAttributes will indicate
>> the device as wakeup capable. With the current implementation,
>> when host sends GET_STATUS request for both interfaces, we will
>> set FUNC_RW_CAP for both. This results in USB3 CV Chapter 9.15
>> (Function Remote Wakeup Test) failures as host expects remote
>> wakeup from both interfaces.
>>
>> The above scenario is just an example, and the failure can be
>> observed if we use configuration with any interface except ECM.
>> Hence avoid configuring remote wakeup capability from composite
>> driver based on bmAttributes, instead use get_status callbacks
>> and let the function drivers decide this.
>>
>> Cc: stable@...nel.org
>> Fixes: 481c225c4802 ("usb: gadget: Handle function suspend feature selector")
>> Signed-off-by: Prashanth K <prashanth.k@....qualcomm.com>
>> ---
>>  drivers/usb/gadget/composite.c | 12 ++++--------
>>  1 file changed, 4 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
>> index 869ad99afb48..5c6da360e95b 100644
>> --- a/drivers/usb/gadget/composite.c
>> +++ b/drivers/usb/gadget/composite.c
>> @@ -2010,16 +2010,12 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
>>  			break;
>>  
>>  		if (f->get_status) {
>> -			status = f->get_status(f);
>> +			/* if D5 is not set, then device is not wakeup capable */
>> +			if (f->config->bmAttributes & USB_CONFIG_ATT_WAKEUP)
> 
> We should allow function to execute get_status regardless of
> USB_CONFIG_ATT_WAKEUP. There are other status beside wakeup.
>
Agree with the first part, I also wanted to remove the explicit check
for USB_CONFIG_ATT_WAKEUP. But anyways kept it since only 2 bits (RW_CAP
and RW) are defined in the spec as the status of GetStatus for an Interface.

Lets do one thing, I'll rearrange it as follows

if (f->get_status) {
	status = f->get_status(f);
	
/* if D5 is not set, then device is not wakeup capable */
if (f->config->bmAttributes & USB_CONFIG_ATT_WAKEUP)
	status &= ~(USB_INTRF_STAT_FUNC_RW_CAP | USB_INTRF_STAT_FUNC_RW);

>> +				status = f->get_status(f);
>> +
>>  			if (status < 0)
>>  				break;
>> -		} else {
>> -			/* Set D0 and D1 bits based on func wakeup capability */
>> -			if (f->config->bmAttributes & USB_CONFIG_ATT_WAKEUP) {
>> -				status |= USB_INTRF_STAT_FUNC_RW_CAP;
> 
> 
> So right now we're not able to configure the function to enable RW
> capable? Perhaps we need to update the composite configfs for this?
> 

The removed code used to set USB_INTRF_STAT_FUNC_RW_CAP even for
interfaces which doesn't have RW capability. Its better to handle this
from function level than from composite.

Regards,
Prashanth K