Re: [PATCH v6 4/4] usb: gadget: udc-core: independent registration of gadgets and gadget drivers

[Peter Chen <peter.chen@freescale.com>]

On Fri, Nov 20, 2015 at 09:54:12AM +0100, Marek Szyprowski wrote:
> From: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> 
> Change behavior during registration of gadgets and
> gadget drivers in udc-core. Instead of previous
> approach when for successful probe of usb gadget driver
> at least one usb gadget should be already registered
> use another one where gadget drivers and gadgets
> can be registered in udc-core independently.
> 
> Independent registration of gadgets and gadget drivers
> is useful for built-in into kernel gadget and gadget
> driver case - because it's possible that gadget is
> really probed only on late_init stage (due to deferred
> probe) whereas gadget driver's probe is silently failed
> on module_init stage due to no any UDC added.
> 
> Also it is useful for modules case - now there is no
> difference what module to insert first: gadget module
> or gadget driver one.
> 
> Tested-by: Maxime Ripard <maxime.ripard@free-electrons.com>
> Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> [simplified code as requested by Alan Stern and Felipe Balbi]
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> ---
>  drivers/usb/gadget/udc/udc-core.c | 43 +++++++++++++++++++++++++++++++--------
>  include/linux/usb/gadget.h        |  2 ++
>  2 files changed, 37 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/usb/gadget/udc/udc-core.c b/drivers/usb/gadget/udc/udc-core.c
> index f76ebc8..461b311 100644
> --- a/drivers/usb/gadget/udc/udc-core.c
> +++ b/drivers/usb/gadget/udc/udc-core.c
> @@ -51,8 +51,12 @@ struct usb_udc {
>  
>  static struct class *udc_class;
>  static LIST_HEAD(udc_list);
> +static LIST_HEAD(gadget_driver_pending_list);
>  static DEFINE_MUTEX(udc_lock);
>  
> +static int udc_bind_to_driver(struct usb_udc *udc,
> +		struct usb_gadget_driver *driver);
> +
>  /* ------------------------------------------------------------------------- */
>  
>  #ifdef	CONFIG_HAS_DMA
> @@ -356,6 +360,7 @@ int usb_add_gadget_udc_release(struct device *parent, struct usb_gadget *gadget,
>  		void (*release)(struct device *dev))
>  {
>  	struct usb_udc		*udc;
> +	struct usb_gadget_driver *driver;
>  	int			ret = -ENOMEM;
>  
>  	udc = kzalloc(sizeof(*udc), GFP_KERNEL);
> @@ -403,6 +408,18 @@ int usb_add_gadget_udc_release(struct device *parent, struct usb_gadget *gadget,
>  	usb_gadget_set_state(gadget, USB_STATE_NOTATTACHED);
>  	udc->vbus = true;
>  
> +	/* pick up one of pending gadget drivers */
> +	list_for_each_entry(driver, &gadget_driver_pending_list, pending) {
> +		if (!driver->udc_name || strcmp(driver->udc_name,
> +						dev_name(&udc->dev)) == 0) {
> +			ret = udc_bind_to_driver(udc, driver);
> +			if (ret)
> +				goto err4;
> +			list_del(&driver->pending);
> +			break;
> +		}
> +	}
> +
>  	mutex_unlock(&udc_lock);
>  
>  	return 0;
> @@ -475,9 +492,16 @@ void usb_del_gadget_udc(struct usb_gadget *gadget)
>  	list_del(&udc->list);
>  	mutex_unlock(&udc_lock);
>  
> -	if (udc->driver)
> +	if (udc->driver) {
> +		struct usb_gadget_driver *driver = udc->driver;
> +
>  		usb_gadget_remove_driver(udc);
>  
> +		mutex_lock(&udc_lock);
> +		list_add(&driver->pending, &gadget_driver_pending_list);
> +		mutex_unlock(&udc_lock);
> +	}
> +
>  	kobject_uevent(&udc->dev.kobj, KOBJ_REMOVE);
>  	flush_work(&gadget->work);
>  	device_unregister(&udc->dev);
> @@ -535,11 +559,7 @@ int usb_gadget_probe_driver(struct usb_gadget_driver *driver)
>  			if (!ret)
>  				break;
>  		}
> -		if (ret)
> -			ret = -ENODEV;
> -		else if (udc->driver)
> -			ret = -EBUSY;
> -		else
> +		if (!ret && !udc->driver)
>  			goto found;
>  	} else {
>  		list_for_each_entry(udc, &udc_list, list) {
> @@ -549,9 +569,12 @@ int usb_gadget_probe_driver(struct usb_gadget_driver *driver)
>  		}
>  	}
>  
> -	pr_debug("couldn't find an available UDC\n");
> +	list_add_tail(&driver->pending, &gadget_driver_pending_list);
> +	pr_info("udc-core: couldn't find an available UDC "
> +			"- added [%s] to list of pending drivers\n",
> +			driver->function);
>  	mutex_unlock(&udc_lock);
> -	return ret;
> +	return 0;
>  found:
>  	ret = udc_bind_to_driver(udc, driver);
>  	mutex_unlock(&udc_lock);
> @@ -577,6 +600,10 @@ int usb_gadget_unregister_driver(struct usb_gadget_driver *driver)
>  			break;
>  		}
>  
> +	if (ret) {
> +		list_del(&driver->pending);
> +		ret = 0;
> +	}
>  	mutex_unlock(&udc_lock);
>  	return ret;
>  }
> diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
> index e11f5a2..a3436bf 100644
> --- a/include/linux/usb/gadget.h
> +++ b/include/linux/usb/gadget.h
> @@ -1014,6 +1014,7 @@ static inline int usb_gadget_activate(struct usb_gadget *gadget)
>   * @driver: Driver model state for this driver.
>   * @udc_name: A name of UDC this driver should be bound to. If udc_name is NULL,
>   * 	this driver will be bound to any available UDC.
> + * @pending: UDC core private data used for deferred probe of this driver.
>   *
>   * Devices are disabled till a gadget driver successfully bind()s, which
>   * means the driver will handle setup() requests needed to enumerate (and
> @@ -1076,6 +1077,7 @@ struct usb_gadget_driver {
>  	struct device_driver	driver;
>  
>  	char			*udc_name;
> +	struct list_head	pending;
>  };
>  
>  

And it seems can't apply for felipe's testing/next which I just rebased
on it.

-- 

Best Regards,
Peter Chen