On Mon, 4 Oct 2010, Felipe Balbi wrote:
> this class will be used to abstract away
> several of the duplicated operations scatered
> among the USB gadget controller drivers.
>
> Later, we can add an atomic notifer to tell
> interested drivers about what's happening
> with the controller. Notifications such as
> suspend, resume, enumerated, etc will be
> useful, at a minimum, for implementing
> usb charger detection.
Why is this implemented in terms of a udc class device? Why not just
associate the attributes with the controller device itself? Is this
for the uevents?
I've never really understood the point of class devices.
> +/**
> + * usb_add_udc - adds a new udc to the udc class driver list
> + * @parent: the parent device to this udc. Usually the controller
> + * driver's device.
> + * @udc: the udc to be added to the list
> + *
> + * Returns zero on success, negative errno otherwise.
> + */
> +int usb_add_udc(struct device *parent, struct usb_udc *udc)
> +{
> + struct device *dev;
> + unsigned long flags;
> + int ret;
> +
> + if (!udc->gadget || !udc->gadget->ops ||
> + !udc->gadget->ops->start) {
> + dev_dbg(parent, "unitializaed gadget\n");
> + return -EINVAL;
> + }
> +
> + dev_vdbg(parent, "registering UDC\n");
> +
> + dev = kzalloc(sizeof(*dev), GFP_KERNEL);
> + if (!dev) {
> + ret = -ENOMEM;
> + goto err1;
> + }
> +
> + spin_lock_irqsave(&udc_lock, flags);
> +
> + device_initialize(dev);
> +
> + dev->class = udc_class;
> + dev->type = &udc_device_type;
> + dev->parent = parent;
> + dev->release = usb_udc_release;
> + dev_set_drvdata(dev, udc);
> + udc->dev = dev;
> + udc->gadget->dev.parent = udc->dev;
> + udc->gadget->dev.release = usb_udc_nop_release;
This causes problems with dummy-hcd. It actually needs to do something
when the gadget device is released.
Why not embed the gadget and the device node directly in the usb_udc
structure, instead of just putting pointers there?
Alan Stern
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