Re: [PATCH] USB: output an error message when the pipe type doesn't match the endpoint type

[Alan Stern <stern@rowland.harvard.edu>]

On Wed, 1 Sep 2010, Simon Arlott wrote:

> > This is okay with me.  If you're serious about not changing the
> > behavior merely because debugging is enabled, you could move this test
> > out of the debug-only region and possibly change the dev_err to
> > dev_dbg.  However doing so might break some devices that are currently
> > working.
> 
> I'd expect that to break potentially many devices, although only cxacru
> stopped working for me. The USB API isn't really suitable for adding
> this type of check because it allows the drivers to get away with too
> much already.

Unlike device hardware, drivers can always be changed.  If adding a 
check will help spot errors, it's probably worthwhile.

> usb_clear_halt() takes a pipe when it really wants the endpoint, the
> pipe type is ignored.

What's wrong with that?  Besides, in the end we shouldn't be using
pipes at all; we should always use pointers to struct
usb_host_endpoint.

> usb_bulk_msg() auto-detects the type between interrupt and bulk, as
> does usb_interrupt_msg() because the latter just calls the former.
> 
> (I think -EINVAL might be a better return code. The pipe isn't broken,
> it doesn't exist.)

Within the kernel, the meanings of the -Exxx error codes are fairly
arbitrary.  But since this code can be passed to userspace you are
right.

Alan Stern