linux-kernel - RE: [PATCH v2 6/9] usb: roles: Find the muxes by also matching against the device node

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Date:   Tue, 12 Feb 2019 10:41:28 +0000
From:   Jun Li <jun.li@....com>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Chen Yu <chenyu56@...wei.com>,
        Hans de Goede <hdegoede@...hat.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 6/9] usb: roles: Find the muxes by also matching
 against the device node

Hi
> -----Original Message-----
> From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> Sent: 2019年2月12日 16:51
> To: Jun Li <jun.li@....com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>; Andy Shevchenko
> <andy.shevchenko@...il.com>; Chen Yu <chenyu56@...wei.com>; Hans de
> Goede <hdegoede@...hat.com>; linux-usb@...r.kernel.org;
> linux-kernel@...r.kernel.org
> Subject: Re: [PATCH v2 6/9] usb: roles: Find the muxes by also matching against the
> device node
> 
> Hi,
> 
> On Tue, Feb 12, 2019 at 06:03:42AM +0000, Jun Li wrote:
> > > > return dev_fwnode(dev->parent) == fwnode;
> > >
> > > That's actually not the case. struct usb_role_switch_desc has a
> > > member for fwnode, and that's what we use with the actual mux
> > > device. Check
> > > usb_role_switch_register():
> > >
> > >         ...
> > >         sw->dev.fwnode = desc->fwnode;
> > >         ...
> > >
> > > Sorry for not realizing it before.
> >
> > So desc->fwnode should be initialized before do usb_role_switch_register()?
> > But seems usb_role_switch_desc is a read-only object so can't be set at runtime.
> 
> It can. Even though usb_role_switch_register() takes read-only parameter, nothing's
> preventing you from passing data even from the stack (the content of the descriptor
> is copied in any case).
> 
> Expecting the descriptor to be read-only just means it can be read-only, but it does
> not have to be.

Understood, thanks.

> @@ -32,6 +32,7 @@ typedef enum usb_role (*usb_role_switch_get_t)(struct
> device *dev);
>   * usb_role_switch_register() before registering the switch.
>   */
>  struct usb_role_switch_desc {
> +	struct fwnode_handle *fwnode;
You may add some description for this new member
/**
 * struct usb_role_switch_desc - USB Role Switch Descriptor
 * @ fwnode 

> 
> > usb_controller_node {
> > 	...
> > 	usb-role-switch;
> >
> > 	port {
> > 		sw_provider_node: endpoint {
> > 			remote-endpoint = <&sw_consumer_node>;
> > 		};
> > 	};
> > };
> >
> > typec_node {
> > 	...
> > 	port {
> > 		sw_consumer_node: endpoint {
> > 			remote-endpoint = <&sw_provider_node>;
> > 		};
> > 	};
> > };
> 
> That looks roughly correct to me.
> 
> 
> thanks,
> 
> --
> heikki