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

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Message-ID: <20191029031223.GA26815@b29397-desktop>
Date:   Tue, 29 Oct 2019 03:12:34 +0000
From:   Peter Chen <peter.chen@....com>
To:     Roger Quadros <rogerq@...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 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.

-- 

Thanks,
Peter Chen