Re: [PATCH] usb: host: Use helper function to get endpoint

[Alan Stern]

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