linux-kernel - Re: [PATCH] usb: cdns3: gadget: Don't manage pullups

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Message-ID: <0c2c901c-a6f2-a81b-f5b1-e3f442d7c1ae@ti.com>
Date:   Tue, 29 Oct 2019 11:37:31 +0200
From:   Roger Quadros <rogerq@...com>
To:     Peter Chen <peter.chen@....com>
CC:     Pawel Laszczak <pawell@...ence.com>,
        "felipe.balbi@...ux.intel.com" <felipe.balbi@...ux.intel.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "nsekhar@...com" <nsekhar@...com>,
        Rahul Kumar <kurahul@...ence.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: cdns3: gadget: Don't manage pullups



On 29/10/2019 05:12, Peter Chen wrote:
> On 19-10-25 12:59:17, Roger Quadros wrote:
>> Peter,
>>
>> On 25/10/2019 06:13, Peter Chen wrote:
>>> On 19-10-23 09:17:45, Pawel Laszczak wrote:
>>>> Hi,
>>>>
>>>> Reviewed-by: Pawel Laszczak <pawell@...ence.com>
>>>
>>> Hi Roger & Pawel,
>>>
>>> Assume gadget function has already enabled, if you switch host mode
>>> to device mode, with your changes, where the device mode will be enabled
>>> again?
>>
>> When it switches from device mode to host the UDC is removed. When we switch
>> back from host to device mode the UDC is added, so,
>>
>> usb_add_gadget_udc_release()-> check_pending_gadget_drivers()->
>> udc_bind_to_driver()->usb_udc_connect_control()->usb_gadget_connect()->
>> gadget->ops->pullup()
> 
> Thanks. I have another question how you decide when to store UDC name
> to /sys/kernel/config/usb_gadget/g1/UDC? Do you have a user daemon program
> to monitor VBUS or external connector? At host mode, the store operation
> will fail due to there is NO UDC.
> 

Yes, user space needs to monitor /sys/class/usb_role/6000000.usb-role-switch/role

When it becomes "device" the UDC is available and it can prepare to configure
the UDC.

Could you please give your Ack for this patch if it is OK? Thanks.

cheers,
-roger

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