linux-kernel - RE: [PATCH v2 5/5] usb:cdns3 Add Cadence USB3 DRD Driver

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Message-ID: <BYAPR07MB4709A8E20953E24E67A801EADD840@BYAPR07MB4709.namprd07.prod.outlook.com>
Date:   Thu, 10 Jan 2019 07:18:50 +0000
From:   Pawel Laszczak <pawell@...ence.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Chen <hzpeterchen@...il.com>
CC:     "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "hdegoede@...hat.com" <hdegoede@...hat.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        "andy.shevchenko@...il.com" <andy.shevchenko@...il.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "rogerq@...com" <rogerq@...com>,
        lkml <linux-kernel@...r.kernel.org>,
        "adouglas@...ence.com" <adouglas@...ence.com>,
        "jbergsagel@...com" <jbergsagel@...com>,
        "nsekhar@...com" <nsekhar@...com>, "nm@...com" <nm@...com>,
        Suresh Punnoose <sureshp@...ence.com>,
        "peter.chen@....com" <peter.chen@....com>,
        Pawel Jez <pjez@...ence.com>, Rahul Kumar <kurahul@...ence.com>
Subject: RE: [PATCH v2 5/5] usb:cdns3 Add Cadence USB3 DRD Driver

Hi, 

>On Thu, Jan 10, 2019 at 09:30:41AM +0800, Peter Chen wrote:
>> On Mon, Dec 24, 2018 at 12:44 AM Pawel Laszczak <pawell@...ence.com> wrote:
>> - debugfs is nice to have feature, I suggest removing it at this
>> initial version. Besides, role switch
>> through /sys is normal feature, the end user may use it at real
>> product, so, it is better at device's
>> /sys entry instead of debugfs.
>>
>> - I don't know why you add "disable" at debugfs, please comment.
>
>As you imply here, no real-world functionality should ever be in
>debugfs as it is an optional system component and kernel code should
>work just fine without it being enabled (as more and more systems are
>disabling it due to the obvious security problems it has.)
>
"disable" it's not required. It's used for testing. It allows to enable/disable the current role.
It can be used for testing eg. connect/disconnect event. 

I mainly test the driver remotely and I can't do connect/disconnect by USB cable. 
"disable" allow me to get trace log from host/device without disconnecting cable:
I'm using the fallowing sequence:
 - load cdns3.ko modules 
 - echo 1 > disable - disable current role
 - echo cdns3:* tracing/set_event 
 - echo 0 > disable  - enable role again 
 - cat tracing/trace. 

Pawel