Re: [PATCH v1 08/12] usb: roles: Add usb role switch notifier.

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

On Mon, Dec 03, 2018 at 11:45:11AM +0800, Yu Chen wrote:
> This patch adds notifier for drivers want to be informed of the usb role switch.

I think in this case it would be good to explain a little for what we
need the notifier for.

> 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>
> Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> Signed-off-by: Yu Chen <chenyu56@huawei.com>
> 
> --
> v0:
> The patch is provided by Heikki Krogerus. I modified and test it
> on Hikey960 platform.

I don't think I actually made a "patch" for this. The "diff" I made
showing the idea does not count, so you should not sign off the patch
with my address.

In this case I believe something like "Suggested-by" should be used
instead of SoB tag:

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

Side note: If this was from me, then there should be "from" line with
my address as well.

> --
> ---
>  drivers/usb/common/roles.c | 20 +++++++++++++++++++-
>  include/linux/usb/role.h   | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 65 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/common/roles.c b/drivers/usb/common/roles.c
> index 0f48090c5c30..bfd7a988b64c 100644
> --- a/drivers/usb/common/roles.c
> +++ b/drivers/usb/common/roles.c
> @@ -21,6 +21,7 @@ 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;
> @@ -50,8 +51,10 @@ 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);
>  
> @@ -59,6 +62,20 @@ 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
> @@ -297,6 +314,7 @@ 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 edc51be4a77c..c97d4be91ada 100644
> --- a/include/linux/usb/role.h
> +++ b/include/linux/usb/role.h
> @@ -40,6 +40,8 @@ struct usb_role_switch_desc {
>  	bool allow_userspace_control;
>  };
>  
> +
> +#if IS_ENABLED(CONFIG_USB_ROLE_SWITCH)
>  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);
> @@ -49,5 +51,49 @@ 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)
> +{
> +	return 0;
> +}
> +
> +static inline enum usb_role usb_role_switch_get_role(struct usb_role_switch *sw)
> +{
> +	return USB_ROLE_NONE;
> +}
> +
> +static inline struct usb_role_switch *usb_role_switch_get(struct device *dev)
> +{
> +	return ERR_PTR(-ENODEV);
> +}
> +
> +static inline void usb_role_switch_put(struct usb_role_switch *sw) { }
> +
> +static inline struct usb_role_switch *
> +usb_role_switch_register(struct device *parent,
> +			 const struct usb_role_switch_desc *desc)
> +{
> +	return ERR_PTR(-ENODEV);
> +}
> +
> +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