[v5,1/2] usb/gadget: Add an EP dispose() callback for EP lifetime tracking

[Felipe Balbi <balbi@kernel.org>]

Hi,

Benjamin Herrenschmidt <benh@kernel.crashing.org> writes:
> Some UDC may want to allocate endpoints dynamically, either because
> the HW supports an arbitrary large number or because (like the Aspeed
> BMC SoCs), the pool of HW endpoints is shared between multiple gadgets.
>
> The allocation side can be done rather easily using the existing
> match_ep() UDC hook.
>
> However we have no good place to "free" them.
>
> This implements a "simple" variant of this, which calls an EP dispose
> callback on all EPs associated with a gadget when the composite device
> gets unbound.
>
> This is required by my upcoming Aspeed vHub driver.
>
> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> ---
>  drivers/usb/gadget/composite.c | 8 ++++++++
>  include/linux/usb/gadget.h     | 1 +
>  2 files changed, 9 insertions(+)
>
> diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
> index 77c7ecca816a..ec99c9cfc1a2 100644
> --- a/drivers/usb/gadget/composite.c
> +++ b/drivers/usb/gadget/composite.c
> @@ -2172,6 +2172,7 @@ int composite_os_desc_req_prepare(struct usb_composite_dev *cdev,
>  void composite_dev_cleanup(struct usb_composite_dev *cdev)
>  {
>  	struct usb_gadget_string_container *uc, *tmp;
> +	struct usb_ep			   *ep, *tmp_ep;
>  
>  	list_for_each_entry_safe(uc, tmp, &cdev->gstrings, list) {
>  		list_del(&uc->list);
> @@ -2193,6 +2194,13 @@ void composite_dev_cleanup(struct usb_composite_dev *cdev)
>  	}
>  	cdev->next_string_id = 0;
>  	device_remove_file(&cdev->gadget->dev, &dev_attr_suspended);
> +
> +	/* Dispose EPs if the UDC driver tracks lifetime */
> +	list_for_each_entry_safe(ep, tmp_ep,
> +				 &cdev->gadget->ep_list, ep_list) {

do you really need this to be safe? You don't seem to be modifying
ep_list here.