On Wed, Aug 24, 2022 at 11:57:25PM +0600, Khalid Masum wrote: > On Wed, Aug 24, 2022 at 8:40 PM Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > Even this is awkward. It's silly to look up the endpoint in a table > > when you already know that it is endpoint 0. Just do: > > > > ep = &udev->ep0; > > > > with no need to check for NULL. > > After further checking, I realized that usb_device udev is created by > ehset_single_step_set_feature and depends on usb_hcd and port. So I do > not get why the endpoint is at udev->ep0. Can you help me with this? udev is not a usb_device structure; it is a _pointer_ to a usb_device structure. The pointer is created when ehset_single_step_set_feature() calls usb_hub_find_child(), but the structure itself gets created long before that, when the USB device is first detected and initialized. You can see this happening where hub_port_connect() calls usb_alloc_dev(). The ep0 field is filled in by hub_port_init() and the routines it calls. Alan Stern
