linux-kernel - Re: [PATCH v5 4/6] usb: roles: add API to get usb_role

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Message-ID: <20190520083601.GE1887@kuha.fi.intel.com>
Date:   Mon, 20 May 2019 11:36:01 +0300
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Biju Das <biju.das@...renesas.com>
Cc:     Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mark Rutland <mark.rutland@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Adam Thomson <Adam.Thomson.Opensource@...semi.com>,
        Li Jun <jun.li@....com>,
        Badhri Jagan Sridharan <badhri@...gle.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Min Guo <min.guo@...iatek.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v5 4/6] usb: roles: add API to get usb_role_switch by node

On Mon, May 20, 2019 at 08:06:41AM +0000, Biju Das wrote:
> Hi Heikki,
> 
> > -----Original Message-----
> > From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> > Sent: Monday, May 20, 2019 9:04 AM
> > To: Chunfeng Yun <chunfeng.yun@...iatek.com>
> > Cc: Rob Herring <robh+dt@...nel.org>; Greg Kroah-Hartman
> > <gregkh@...uxfoundation.org>; Mark Rutland <mark.rutland@....com>;
> > Matthias Brugger <matthias.bgg@...il.com>; Adam Thomson
> > <Adam.Thomson.Opensource@...semi.com>; Li Jun <jun.li@....com>;
> > Badhri Jagan Sridharan <badhri@...gle.com>; Hans de Goede
> > <hdegoede@...hat.com>; Andy Shevchenko
> > <andy.shevchenko@...il.com>; Min Guo <min.guo@...iatek.com>;
> > devicetree@...r.kernel.org; linux-kernel@...r.kernel.org; linux-
> > usb@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-
> > mediatek@...ts.infradead.org; Biju Das <biju.das@...renesas.com>; Linus
> > Walleij <linus.walleij@...aro.org>
> > Subject: Re: [PATCH v5 4/6] usb: roles: add API to get usb_role_switch by
> > node
> > 
> > On Mon, May 20, 2019 at 10:39:11AM +0800, Chunfeng Yun wrote:
> > > Hi,
> > > On Fri, 2019-05-17 at 16:05 +0300, Heikki Krogerus wrote:
> > > > Hi,
> > > >
> > > > On Fri, May 17, 2019 at 01:37:36PM +0300, Heikki Krogerus wrote:
> > > > > On Tue, May 14, 2019 at 04:47:21PM +0800, Chunfeng Yun wrote:
> > > > > > Add fwnode_usb_role_switch_get() to make easier to get
> > > > > > usb_role_switch by fwnode which register it.
> > > > > > It's useful when there is not device_connection registered
> > > > > > between two drivers and only knows the fwnode which register
> > > > > > usb_role_switch.
> > > > > >
> > > > > > Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
> > > > > > Tested-by: Biju Das <biju.das@...renesas.com>
> > > > >
> > > > > Acked-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> > > >
> > > > Hold on. I just noticed Rob's comment on patch 2/6, where he points
> > > > out that you don't need to use device graph since the controller is
> > > > the parent of the connector. Doesn't that mean you don't really need
> > > > this API?
> > > No, I still need it.
> > > The change is about the way how to get fwnode; when use device graph,
> > > get fwnode by of_graph_get_remote_node(); but now will get fwnode by
> > > of_get_parent();
> > 
> > OK, I get that, but I'm still not convinced about if something like this function
> > is needed at all. I also have concerns regarding how you are using the
> > function. I'll explain in comment to the patch 5/6 in this series...
> 
> FYI, Currently  I am also using this api in my patch series.
> https://patchwork.kernel.org/patch/10944637/

Yes, and I have the same question for you I jusb asked in comment I
added to the patch 5/6 of this series. Why isn't usb_role_switch_get()
enough?

thanks,

-- 
heikki