Re: USB OTG HNP (can you find any other appropriate TLAs?)
David Brownell <[email protected]>
| Newsgroups | gmane.linux.usb.devel |
|---|---|
| Message-ID | <[email protected]> |
On Thursday 24 May 2007, Alan Stern wrote:
> Dave:
>
> In this section from usb_new_device():
>
> if (!is_targeted(udev)) {
>
> /* Maybe it can talk to us, though we can't talk to it.
> * (Includes HNP test device.)
> */
> if (udev->bus->b_hnp_enable || udev->bus->is_b_host) {
> err = __usb_port_suspend(udev, udev->bus->otg_port);
> if (err < 0)
> dev_dbg(&udev->dev, "HNP fail, %d\n", err);
> }
>
> Is there any reason to call __usb_port_suspend() rather than
> usb_port_suspend()?
Maybe not any more.
> After all, an OTG device is required to have no
> more than one USB connection, so the port number would always be equal
> to udev->portnum and to 1.
Not true. It's perfectly legit for a host to have multiple host
ports, with only one of them being OTG-capable. Not uncommon either;
it's a simple implementation strategy (combining existing silicon IP
with an OTG engine), and board designers find serial busses like USB
are handy as a way to integrate various devices ... simple to route
on the boards, only two pins, and so forth. It's not just a way to
connect external devices.
- Dave
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