Re: [RFC][PATCH 2/3] usb: roles: Add usb role switch notifier.

[Hans de Goede <hdegoede@redhat.com>]

Hi John,

On 03-10-2019 01:16, John Stultz wrote:
> From: Yu Chen <chenyu56@huawei.com>
> 
> This patch adds notifier for drivers want to be informed of the usb role
> switch.

I do not see any patches in this series actually using this new
notifier.

Maybe it is best to drop this patch until we actually have in-kernel
users of this new API show up ?

Regards,

Hans


> 
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
> Cc: Chunfeng Yun <chunfeng.yun@mediatek.com>
> Cc: Yu Chen <chenyu56@huawei.com>
> Cc: Felipe Balbi <balbi@kernel.org>
> Cc: Hans de Goede <hdegoede@redhat.com>
> Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
> Cc: Jun Li <lijun.kernel@gmail.com>
> Cc: Valentin Schneider <valentin.schneider@arm.com>
> Cc: linux-usb@vger.kernel.org
> Cc: devicetree@vger.kernel.org
> Suggested-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> Signed-off-by: Yu Chen <chenyu56@huawei.com>
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> ---
>   drivers/usb/roles/class.c | 35 ++++++++++++++++++++++++++++++++++-
>   include/linux/usb/role.h  | 16 ++++++++++++++++
>   2 files changed, 50 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/roles/class.c b/drivers/usb/roles/class.c
> index 94b4e7db2b94..418e762d5d72 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 +61,35 @@ 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)
> +{
> +	int ret = blocking_notifier_chain_register(&sw->nh, nb);
> +	enum usb_role role;
> +
> +	if (ret)
> +		return ret;
> +
> +	/* Initialize the notifier that was just registered */
> +	mutex_lock(&sw->lock);
> +	if (sw->get)
> +		role = sw->get(sw->dev.parent);
> +	else
> +		role = sw->role;
> +	blocking_notifier_call_chain(&sw->nh, role, NULL);
> +	mutex_unlock(&sw->lock);
> +
> +	return 0;
> +}
> +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
> @@ -296,6 +328,7 @@ 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 2d77f97df72d..8dbf7940b7da 100644
> --- a/include/linux/usb/role.h
> +++ b/include/linux/usb/role.h
> @@ -54,6 +54,10 @@ 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)
> @@ -87,6 +91,18 @@ 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 */
>