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

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Message-ID: <20190410102239.GG20058@kuha.fi.intel.com>
Date:   Wed, 10 Apr 2019 13:22:39 +0300
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
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>,
        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, 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. Why not just assign the
parent's fwnode for the mux as well?

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);

> +	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,

-- 
heikki