Re: [PATCH v6 3/5] usb: gadget: Add function wakeup support

[Thinh Nguyen]

Hi Elson,

On Mon, Mar 06, 2023, Elson Roy Serrao wrote:
> A function which is in function suspend state has to send a
> function wake notification to the host in case it needs to

This should be rephrased. The device doesn't send wakeup device
notification while in suspend.

> exit from this state and resume data transfer. Add support to
> handle such requests by exposing a new gadget op.

Please provide more info in the commit message describing the change.
You did more than just adding a new gadget op here.

> 
> Signed-off-by: Elson Roy Serrao <quic_eserrao@xxxxxxxxxxx>
> ---
>  drivers/usb/gadget/composite.c | 40 ++++++++++++++++++++++++++++++++++++++++
>  include/linux/usb/composite.h  |  6 ++++++
>  include/linux/usb/gadget.h     |  1 +
>  3 files changed, 47 insertions(+)
> 
> diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
> index 7512854..7ae78c05 100644
> --- a/drivers/usb/gadget/composite.c
> +++ b/drivers/usb/gadget/composite.c
> @@ -492,6 +492,46 @@ int usb_interface_id(struct usb_configuration *config,
>  }
>  EXPORT_SYMBOL_GPL(usb_interface_id);
>  
> +/**
> + * usb_func_wakeup - sends function wake notification to the host.
> + * @func: function that sends the remote wakeup notification.
> + *
> + * Applicable only to enhanced super speed devices when usb functions

Enhanced SuperSpeed devices can operate in usb2 speeds. This should be
rephased to refer to the operating speed instead.

> + * are put in function suspend state and armed for function remote wakeup.
> + * On completion, function wake notification is sent. If the device is in
> + * low power state it tries to bring the device to active state before
> + * sending the wake notification. Since it is a synchronous call, caller
> + * must take care of not calling it in interrupt context. For non enhanced
> + * super speed devices operating in lower speeds returns negative errno.

Same here. Enhanced SuperSpeed devices can operate in lower speeds.

It's a good idea that you discarded creating usb_gadget_func_wakeup().
In usb_gadget_wakeup(), we place the burden of checking whether the host
enabled remote wakeup in the UDC driver. For usb_func_wakeup(), you
place the burden of checking whether the host enabled function remote
wakeup in the composite layer. If we have usb_gadget_func_wakeup(), then
you may need to clarify how to handle that.

> + *
> + * Returns zero on success, else negative errno.
> + */
> +int usb_func_wakeup(struct usb_function *func)
> +{
> +	struct usb_gadget	*gadget = func->config->cdev->gadget;
> +	int			id;
> +
> +	if (!func->func_wakeup_armed) {
> +		ERROR(func->config->cdev, "not armed for func remote wakeup\n");
> +		return -EINVAL;
> +	}
> +
> +	if (!gadget->ops->func_wakeup)
> +		return -EOPNOTSUPP;

Maybe this check should go first.

> +
> +	for (id = 0; id < MAX_CONFIG_INTERFACES; id++)
> +		if (func->config->interface[id] == func)
> +			break;
> +
> +	if (id == MAX_CONFIG_INTERFACES) {
> +		ERROR(func->config->cdev, "Invalid function\n");
> +		return -EINVAL;
> +	}
> +
> +	return gadget->ops->func_wakeup(gadget, id);
> +}
> +EXPORT_SYMBOL_GPL(usb_func_wakeup);
> +
>  static u8 encode_bMaxPower(enum usb_device_speed speed,
>  		struct usb_configuration *c)
>  {
> diff --git a/include/linux/usb/composite.h b/include/linux/usb/composite.h
> index d949e91..a2448e9 100644
> --- a/include/linux/usb/composite.h
> +++ b/include/linux/usb/composite.h
> @@ -150,6 +150,9 @@ struct usb_os_desc_table {
>   *	GetStatus() request when the recipient is Interface.
>   * @func_suspend: callback to be called when
>   *	SetFeature(FUNCTION_SUSPEND) is reseived
> + * @func_suspended: Indicates whether the function is in function suspend state.
> + * @func_wakeup_armed: Indicates whether the function is armed by the host for
> + *	wakeup signaling.
>   *
>   * A single USB function uses one or more interfaces, and should in most
>   * cases support operation at both full and high speeds.  Each function is
> @@ -220,6 +223,8 @@ struct usb_function {
>  	int			(*get_status)(struct usb_function *);
>  	int			(*func_suspend)(struct usb_function *,
>  						u8 suspend_opt);
> +	bool			func_suspended;
> +	bool			func_wakeup_armed;
>  	/* private: */
>  	/* internals */
>  	struct list_head		list;
> @@ -241,6 +246,7 @@ int config_ep_by_speed_and_alt(struct usb_gadget *g, struct usb_function *f,
>  
>  int config_ep_by_speed(struct usb_gadget *g, struct usb_function *f,
>  			struct usb_ep *_ep);
> +int usb_func_wakeup(struct usb_function *func);
>  
>  #define	MAX_CONFIG_INTERFACES		16	/* arbitrary; max 255 */
>  
> diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
> index 1d79612..75bda078 100644
> --- a/include/linux/usb/gadget.h
> +++ b/include/linux/usb/gadget.h
> @@ -310,6 +310,7 @@ struct usb_udc;
>  struct usb_gadget_ops {
>  	int	(*get_frame)(struct usb_gadget *);
>  	int	(*wakeup)(struct usb_gadget *);
> +	int	(*func_wakeup)(struct usb_gadget *gadget, int intf_id);
>  	int	(*set_remote_wakeup)(struct usb_gadget *, int set);
>  	int	(*set_selfpowered) (struct usb_gadget *, int is_selfpowered);
>  	int	(*vbus_session) (struct usb_gadget *, int is_active);
> -- 
> 2.7.4
> 

Thanks,
Thinh