Re: [PATCH v5 09/13] usb: roles: Add usb role switch notifier.

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

On Fri, Mar 29, 2019 at 12:14:05PM +0800, Yu Chen wrote:
> This patch adds notifier for drivers want to be informed of the usb role
> switch.
> 
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> Cc: Hans de Goede <hdegoede@redhat.com>
> Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
> Cc: John Stultz <john.stultz@linaro.org>
> Suggested-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> Signed-off-by: Yu Chen <chenyu56@huawei.com>

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

> ---
> v5:
> * Split the patch into two patches, the first one introduces stubs for the
> exiting functions, and this patch adds notifier functions.
> ---
> ---
>  drivers/usb/roles/class.c | 20 +++++++++++++++++++-
>  include/linux/usb/role.h  | 16 ++++++++++++++++
>  2 files changed, 35 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/roles/class.c b/drivers/usb/roles/class.c
> index f45d8df5cfb8..e2caaa665d6e 100644
> --- a/drivers/usb/roles/class.c
> +++ b/drivers/usb/roles/class.c
> @@ -20,6 +20,7 @@ struct usb_role_switch {
>  	struct device dev;
>  	struct mutex lock; /* device lock*/
>  	enum usb_role role;
> +	struct blocking_notifier_head nh;
>  
>  	/* From descriptor */
>  	struct device *usb2_port;
> @@ -49,8 +50,10 @@ int usb_role_switch_set_role(struct usb_role_switch *sw, enum usb_role role)
>  	mutex_lock(&sw->lock);
>  
>  	ret = sw->set(sw->dev.parent, role);
> -	if (!ret)
> +	if (!ret) {
>  		sw->role = role;
> +		blocking_notifier_call_chain(&sw->nh, role, NULL);
> +	}
>  
>  	mutex_unlock(&sw->lock);
>  
> @@ -58,6 +61,20 @@ int usb_role_switch_set_role(struct usb_role_switch *sw, enum usb_role role)
>  }
>  EXPORT_SYMBOL_GPL(usb_role_switch_set_role);
>  
> +int usb_role_switch_register_notifier(struct usb_role_switch *sw,
> +				      struct notifier_block *nb)
> +{
> +	return blocking_notifier_chain_register(&sw->nh, nb);
> +}
> +EXPORT_SYMBOL_GPL(usb_role_switch_register_notifier);
> +
> +int usb_role_switch_unregister_notifier(struct usb_role_switch *sw,
> +					struct notifier_block *nb)
> +{
> +	return blocking_notifier_chain_unregister(&sw->nh, nb);
> +}
> +EXPORT_SYMBOL_GPL(usb_role_switch_unregister_notifier);
> +
>  /**
>   * usb_role_switch_get_role - Get the USB role for a switch
>   * @sw: USB role switch
> @@ -271,6 +288,7 @@ usb_role_switch_register(struct device *parent,
>  		return ERR_PTR(-ENOMEM);
>  
>  	mutex_init(&sw->lock);
> +	BLOCKING_INIT_NOTIFIER_HEAD(&sw->nh);
>  
>  	sw->allow_userspace_control = desc->allow_userspace_control;
>  	sw->usb2_port = desc->usb2_port;
> diff --git a/include/linux/usb/role.h b/include/linux/usb/role.h
> index da2b9641b877..99d8b8e4fe61 100644
> --- a/include/linux/usb/role.h
> +++ b/include/linux/usb/role.h
> @@ -53,6 +53,10 @@ struct usb_role_switch *
>  usb_role_switch_register(struct device *parent,
>  			 const struct usb_role_switch_desc *desc);
>  void usb_role_switch_unregister(struct usb_role_switch *sw);
> +int usb_role_switch_register_notifier(struct usb_role_switch *sw,
> +				      struct notifier_block *nb);
> +int usb_role_switch_unregister_notifier(struct usb_role_switch *sw,
> +					struct notifier_block *nb);
>  #else
>  static inline int usb_role_switch_set_role(struct usb_role_switch *sw,
>  		enum usb_role role)
> @@ -80,6 +84,18 @@ usb_role_switch_register(struct device *parent,
>  }
>  
>  static inline void usb_role_switch_unregister(struct usb_role_switch *sw) { }
> +
> +static int usb_role_switch_register_notifier(struct usb_role_switch *sw,
> +				      struct notifier_block *nb)
> +{
> +	return -ENODEV;
> +}
> +
> +static int usb_role_switch_unregister_notifier(struct usb_role_switch *sw,
> +					struct notifier_block *nb)
> +{
> +	return -ENODEV;
> +}
>  #endif
>  
>  #endif /* __LINUX_USB_ROLE_H */
> -- 
> 2.15.0-rc2

thanks,

-- 
heikki