On Sat, Aug 01, 2020 at 06:53:40AM +0000, Peter Chen wrote:
> > So, the basic routine should like below. I thought the usb_gadget should be
> > deallocated before the UDC driver remove itself (UDC device is the parent of
> > usb_gadget device), I may not need to wrong about it, it is just a memory region, it
> > could release later.
> >
> > xxx_udc_release(struct device *gadget_dev) {
> > struct usb_gadget *gadget = container_of(gadget_dev, struct
> > usb_gadget, dev);
> > kfree(gadget);
> > }
> >
> >
> > xxx_udc_probe(pdev)
> > {
> > udc_priv_data = kzalloc(sizeof(*udc_priv_data), GFP_KERNEL);
> > gadget = kzalloc(sizeof(struct usb_gadget), GFP_KERNEL);
> > udc_priv_data->gadget = gadget;
> > ...
> > usb_add_gadget_udc_release(&pdev->dev, gadget, xxx_udc_release);
> >
> > }
> >
> > At xxx_udc_remove(pdev)
> > {
> > usb_del_gadget_udc(udc_priv_data->gadget);
> > /* need to never reference udc_priv_data->gadget any more */
> > udc_priv_data other deinit;
> > kfree(udc_priv_data);
> > }
That would work. It doesn't have to be done exactly this way.
Depending on the driver's needs, you could do:
xxx_udc_release(struct device *dev)
{
udc_priv_data = dev_get_drvdata(dev);
kfree(udc_priv_data);
}
xxx_udc_probe(pdev)
{
udc_priv_data = kzalloc(sizeof(*udc_priv_data), GFP_KERNEL);
dev_set_drvdata(&udc_priv_data->gadget.dev, udc_priv_data);
platform_set_drvdata(pdev, udc_priv_data);
...
usb_add_gadget_udc_release(&pdev->dev, &udc_priv_data->gadget,
xxx_udc_release);
}
xxx_udc_remove(pdev)
{
udc_priv_data = platform_get_drvdata(pdev);
usb_del_gadget_udc(&udc_priv_data->gadget);
}
In other words, embed the struct gadget inside the udc_priv_data
structure. The difference is whether you want to keep the udc_priv_data
structure hanging around even while the controller is in host mode; if
you do then your approach (a separate struct gadget) is better. For a
peripheral-only controller, my approach would be better.
> > Since all structures xxx_udc_release uses are common one, it could replace
> > usb_udc_nop_release at udc/core.c.
Yes, it could. But first all the UDC drivers would have to be modified.
> Since gadget structure is allocated at UDC drivers, I think it should be freed at
> the same place. Current common release function at udc/core.c may not a
> good idea per our discussion.
Agreed.
Alan Stern
