Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Fri, 22 Mar 2019 09:04:04 -0500
From:   Bin Liu <b-liu@ti.com>
To:     Maxime Ripard <maxime.ripard@bootlin.com>
CC:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Paul Kocialkowski <contact@paulk.fr>,
        Paul Kocialkowski <paul.kocialkowski@bootlin.com>,
        <linux-kernel@vger.kernel.org>, <linux-usb@vger.kernel.org>,
        Chen-Yu Tsai <wens@csie.org>
Subject: Re: [PATCH] usb: musb: Support gadget mode when the port is set to
 dual role
Message-ID: <20190322140404.GH25852@uda0271908>
Mail-Followup-To: Bin Liu <b-liu@ti.com>,
        Maxime Ripard <maxime.ripard@bootlin.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Paul Kocialkowski <contact@paulk.fr>,
        Paul Kocialkowski <paul.kocialkowski@bootlin.com>,
        linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org,
        Chen-Yu Tsai <wens@csie.org>
References: <1522324644.1746.19.camel@bootlin.com>
 <20180420142524.GB29011@uda0271908>
 <2db056d6f65ecbcdc4f31a37fe2e1b1ddfb93c87.camel@paulk.fr>
 <20180421143426.GA10632@LTA0271908.dhcp.ti.com>
 <20190321130133.zllt5pqbrhiecoch@flea>
 <20190321164138.GB11121@kroah.com>
 <20190322124622.GB25852@uda0271908>
 <20190322130953.kb4llrtz2nriyfbu@flea>
 <20190322132846.GD25852@uda0271908>
 <20190322134630.c4cauwj5smxvj77y@flea>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <20190322134630.c4cauwj5smxvj77y@flea>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi all,

On Fri, Mar 22, 2019 at 02:46:30PM +0100, Maxime Ripard wrote:
> >
> > Again, think about an embedded product,
> 
> That's all I'm thinking about.
> 
> > if dr_mode is 'otg' which indicates the peripheral mode will be used
> > at some point
> 
> No, it indicates that it *might* be used at some point, based on a
> number of external factors, including:
>   - Whether or not the user has plugged something in the connected USB
>     connector
>   - If they did so, how the ID pin has been wired (and therefore, is
>     a device or a host on the other end)
>   - And how the system designer decided to configure their kernel and
>     userspace.
> 
> > when and how to load the gadget driver if it is not loaded
> > automatically when Linux boots up? the end user doesn't have access
> > to the console.
> 
> An application could load it. And really, we start seeing SoCs in more
> and more pc-like devices, including with mUSB, so I don't think we
> should be making assumptions here.
> 
> How do you think Fedora, Ubuntu or Debian would behave here?
> 
> > > Because no other controller requires it and therefore it's not
> > > standard and violates the principle of least surprise?
> >
> > I know no other controller does this, but this doesn't mean it is not
> > standard.
> 
> I'm pretty sure that would be the definition of "standard", or of a
> norm at least.
> 
> > > And even without taking this into account, there's also the fact that
> > > while the *hardware* can do dual role, the software might decide
> > > otherwise. If I don't want to have support for any gadget (at all) in
> > > the end system, then why should I be forced to compile and load
> > > something I don't even want to use in the first place?
> >
> > then dr_mode should be set to 'host' instead, you don't have to load a
> > gadget if peripheral mode will never be used.
> 
> No. The hardware is perfectly capable of using OTG. The software has
> been configured not to.

I don't think the argument will lead to anywhere. Let's stop arguing
here, so that you can spend time to fix the driver if you want to.

Regards,
-Bin.