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

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Message-ID: <2cc61d5d-656b-49d6-9d09-98c4368b1fc8@oss.qualcomm.com>
Date: Thu, 10 Apr 2025 11:38:03 +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 10-04-25 03:42 am, Thinh Nguyen wrote:
> On Wed, Apr 09, 2025, Thinh Nguyen wrote:
>> On Wed, Apr 09, 2025, Prashanth K wrote:
>>>
>>>
>>> On 09-04-25 06:25 am, Thinh Nguyen wrote:
>>>>
>>>> Not at the gadget level, I mean to create a configfs attribute common
>>>> across different functions to allow the user to enable/disable the
>>>> function wakeup capability via the configfs when you setup the function.
>>>>
>>>> What do you think?
>>>>
>>>> Thanks,
>>>> Thinh
>>>
>>> Thats a good idea, in fact I had the same thought. But thought of doing
>>> it later since its beyond the scope of this patch/series.
>>
>> The way you have it done now forces a usb3x function driver to implement
>> f->get_status to be able to respond with function wakeup capable.
>> Previously, we automatically enable function wakeup capability for all
>> functions if the USB_CONFIG_ATT_WAKEUP is set.

Currently function wakeup is implemented only on f_ecm and others don't
have the capability, so the expectation is functions should add add the
get_status callbacks while implementing remote/func wakeup and mark
itself and RW/FW capable. And if get_status callback is not there, then
func is not FW capable.

Current implementation sets RW/FW capability to all interfaces if
USB_CONFIG_ATT_WAKEUP is set (which is not right). I have provided an
example in the commit text where we incorrectly set FW capability.
>>
>> Arguably, this can cause a regression for remote capable devices to
>> operate in usb3 speeds.
> 
> Sorry typos: I mean arguably, this can cause a regression for remote
> wake capable devices to perform remote wakeup in usb3 speed.
> 
> BR,
> Thinh
> 
>>
>>>
>>> We can add a configfs attribute to enable/disable FUNC_RW_CAP, and
>>> functions can return get_status() based on the attribute.
>>>
>>
>> That would be great! This would fit this series perfectly. Let me know
>> if there's an issue.
>>
I seriously think we can take it out of this series and do that
separately. The intention of this series was to fix the wakeup
operations. And enable/disable func_wakeup from function driver would be
a new implementation. Ill take it up after this.

Regards,
Prashanth K