linux-kernel - Re: [v3 PATCH 4/6] usb: roles: add API to get usb_role

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Date:   Thu, 11 Apr 2019 11:11:09 +0800
From:   Chunfeng Yun <chunfeng.yun@...iatek.com>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.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>,
        Alan Stern <stern@...land.harvard.edu>,
        <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>
Subject: Re: [v3 PATCH 4/6] usb: roles: add API to get usb_role_switch by
 node

On Wed, 2019-04-10 at 13:22 +0300, Heikki Krogerus wrote:
> On Wed, Apr 03, 2019 at 10:09:12AM +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>
> > ---
> > v3 changes:
> >   1. use fwnodes instead of node suggested by Andy
> >   2. rebuild the API suggested by Heikki
> > 
> > v2 no changes
> > ---
> >  drivers/usb/roles/class.c | 31 +++++++++++++++++++++++++++++++
> >  include/linux/usb/role.h  |  2 ++
> >  2 files changed, 33 insertions(+)
> > 
> > diff --git a/drivers/usb/roles/class.c b/drivers/usb/roles/class.c
> > index f45d8df5cfb8..5ecb57f8960b 100644
> > --- a/drivers/usb/roles/class.c
> > +++ b/drivers/usb/roles/class.c
> > @@ -12,6 +12,7 @@
> >  #include <linux/device.h>
> >  #include <linux/module.h>
> >  #include <linux/mutex.h>
> > +#include <linux/of.h>
> >  #include <linux/slab.h>
> >  
> >  static struct class *role_class;
> > @@ -135,6 +136,36 @@ struct usb_role_switch *usb_role_switch_get(struct device *dev)
> >  }
> >  EXPORT_SYMBOL_GPL(usb_role_switch_get);
> >  
> > +static int __switch_match_fwnode(struct device *dev, const void *fwnode)
> > +{
> > +	return dev_fwnode(dev->parent) == (const struct fwnode_handle *)fwnode;
> > +}
> 
> I don't think this is actually needed. 
Yes, you are right

> Why not just assign the
> parent's fwnode for the mux as well?
will do it in next version

> 
> I'll add an example to the patch 6/6 in this series.
> 
> > +/**
> > + * fwnode_usb_role_switch_get - Find USB role switch by it's parent fwnode
> > + * @fwnode: The fwnode that register USB role switch
> > + *
> > + * Finds and returns role switch registered by @fwnode. The reference count
> > + * for the found switch is incremented.
> > + */
> > +struct usb_role_switch *
> > +fwnode_usb_role_switch_get(struct fwnode_handle *fwnode)
> > +{
> > +	struct usb_role_switch *sw;
> > +	struct device *dev;
> > +
> > +	dev = class_find_device(role_class, NULL, fwnode,
> > +				__switch_match_fwnode);
> 
> So here you can then reuse switch_fwnode_match():
> 
> 	dev = class_find_device(role_class, NULL, fwnode, switch_fwnode_match);
I make a fast test, it works, thanks a lot Heikki

> 
> > +	if (!dev)
> > +		return ERR_PTR(-EPROBE_DEFER);
> > +
> > +	sw = to_role_switch(dev);
> > +	WARN_ON(!try_module_get(sw->dev.parent->driver->owner));
> > +
> > +	return sw;
> > +}
> > +EXPORT_SYMBOL_GPL(fwnode_usb_role_switch_get);
> > +
> >  /**
> >   * usb_role_switch_put - Release handle to a switch
> >   * @sw: USB Role Switch
> > diff --git a/include/linux/usb/role.h b/include/linux/usb/role.h
> > index c05ffa6abda9..d21cd55d9e45 100644
> > --- a/include/linux/usb/role.h
> > +++ b/include/linux/usb/role.h
> > @@ -46,6 +46,8 @@ int usb_role_switch_set_role(struct usb_role_switch *sw, enum usb_role role);
> >  enum usb_role usb_role_switch_get_role(struct usb_role_switch *sw);
> >  struct usb_role_switch *usb_role_switch_get(struct device *dev);
> >  void usb_role_switch_put(struct usb_role_switch *sw);
> > +struct usb_role_switch *
> > +fwnode_usb_role_switch_get(struct fwnode_handle *fwnode);
> >  
> >  struct usb_role_switch *
> >  usb_role_switch_register(struct device *parent,
> > -- 
> > 2.20.1
> 
> thanks,
>