Re: [Libusb-win32-devel] Everything but usb_bulk_read works...

[Adam K. <akr...@ro...>]

On Mon, Jun 11, 2007 at 03:47:31PM +0100, Dave Higton wrote:
> > -----Original Message-----
> > From: lib...@li... 
> > [mailto:lib...@li...] On 
> > Behalf Of Adam Kropelin
> > Sent: 2007 June 11 15:43
> > To: lib...@li...
> > Subject: Re: [Libusb-win32-devel] Everything but 
> > usb_bulk_read works...
> > 
> > On Mon, Jun 11, 2007 at 03:23:38PM +0100, Dave Higton wrote:
> > > 
> > > Error 22 is an invalid parameter.  Input endpoint addresses
> > > have to have the top bit set - this is incompatible with the
> > > Linux version.
> > 
> > It's not incompatible at all. Not setting that bit is a bug on any
> > platform. It just so happens that Linux lets you get away with it.
> 
> It depends on your POV.  When you talk to somebody, do you refer to
> endpoint 0x81 or endpoint 1?  I refer to 1, and I bet you do too.
> Linux has explicit code to set the top bit so that either is equally
> valid.

There is an argument to made for the API to be forgiving; you're
performing a read, so obviously you must have meant to provide an input
endpoint address. Since you didn't, the library will fix it up for
you. That type of API makes me uncomfortable; I don't like an API that
thinks it knows more about what I want to do than me...but some 
people like to program that way. There's also an argument to be made 
for consistency; not every API call can easily do such a fixup for you. 
See usb_resetep(), for example. That one is even explicitly documented.

Personally I prefer consistency and exactness: Supply the actual
endpoint address, as specified in bEndpointAddress. Since we have to do
that for some API calls already, its best to do it for all of them.

--Adam