linux-kernel - Re: [PATCH v5] usb: common: usb-conn-gpio: Set last role to unknown before initial detection

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Message-ID: <b14dd204-180d-8035-3eaf-8a53692ef546@quicinc.com>
Date:   Tue, 30 May 2023 01:08:58 +0530
From:   Prashanth K <quic_prashk@...cinc.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5] usb: common: usb-conn-gpio: Set last role to unknown
 before initial detection



On 30-05-23 12:31 am, Greg Kroah-Hartman wrote:
> On Tue, May 30, 2023 at 12:00:15AM +0530, Prashanth K wrote:
>>
>>
>> On 28-05-23 05:03 pm, Greg Kroah-Hartman wrote:
>>>>>> diff --git a/drivers/usb/common/usb-conn-gpio.c b/drivers/usb/common/usb-conn-gpio.c
>>>>>> index e20874c..30bdb81 100644
>>>>>> --- a/drivers/usb/common/usb-conn-gpio.c
>>>>>> +++ b/drivers/usb/common/usb-conn-gpio.c
>>>>>> @@ -257,6 +257,9 @@ static int usb_conn_probe(struct platform_device *pdev)
>>>>>>     	platform_set_drvdata(pdev, info);
>>>>>>     	device_set_wakeup_capable(&pdev->dev, true);
>>>>>> +	/* Set last role to unknown before performing the initial detection */
>>>>>> +	info->last_role = USB_ROLE_UNKNOWN;
>>>>>
>>>>> Shouldn't last_role have already been set to 0?  If so, why not just
>>>>> have this enum value be 0?
>>>> Last role would be 0 during first detection, that's the problem here.
>>>> During initial detection, if the the new role is detected as USB_ROLE_NONE
>>>> (0), then we wouldn't call the set_role(). But it should send the current
>>>> role to gadget after the inital detection.
>>>
>>> So you are hoping that the old enum type is still assigned to 0?  That's
>>> brave, please make it explicit otherwise it's very hard to follow or
>>> ensure that this really will happen.  And most of all, document it so
>>> that that value remains 0 in the future, otherwise a list of enum types
>>> without explicit values are seen as if the values do not matter.
>>>
>>> thanks,
>>>
>>> greg k-h
>>
>> So I think it would be better to add USB_ROLE_UNKNOWN towards the end of
>> enum usb_role, so that we can avoid explicit declaration. Is that fine?
>>
>>   enum usb_role {
>>   	USB_ROLE_NONE,
>>   	USB_ROLE_HOST,
>>   	USB_ROLE_DEVICE,
>> +	USB_ROLE_UNKNOWN,
> 
> Either is fine, be explicit, or not, just don't mix the two please.
> 
> thanks,
> 
> greg k-h

Thanks for the suggestion, will update it in next patch.

Regards,
Prashanth K