Re: [Xen-devel] [PATCH V6 3/7] libxl: add pvusb API

["Chun Yan Liu" <cyliu@xxxxxxxx>]

>>> On 9/11/2015 at 09:26 PM, in message <1441978018.3549.33.camel@xxxxxxxxxx>, 
>>> Ian
Campbell <ian.campbell@xxxxxxxxxx> wrote: 
> On Thu, 2015-09-10 at 23:42 -0600, Chun Yan Liu wrote: 
> >  
> > > Do these fields have any particular size requirements arising from e.g.  
> the  
> > > USB spec or from possible dom0 implementations?  
> > >   
> > > If they have a well defined fixed size from a USB spec then maybe we 
> > > could  
> > > use the appropriate fixed size types?  
> >  
> > Di> dn't see the size limitation. In Linux kernel code, busnum and devnum  
> (here 
> > 'hostbus, hostaddr') are both 'int' type. 
>  
> Is that a Linux-specific implementation detail or a fundamental property of 
> USB? We should be designing the interface around Linux implementation 
> details. It seems like something in the USB spec ought to define precisely 
> the number of bits in both a bus number and a device address within that 
> bus. 

Have a look at USB 2.0 Spec, it has some description on Device Address: a 
seven-bit
value representing the address of the debvice on USB. (up to 127 devices). So 
 int8 is appropriate.
No description to Bus Num.

-Chunyan
>  
> >  And idProduct and idVendor are 'u16'. 
>  
> That's a USB spec thing, I think, so int16 in the IDL seems appropriate. 
>  
> Ian. 
>  
>  



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