Re: [RFC/PATCH 02/12] usb: gadget: change USB version to USB3.0

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On Fri, 8 Apr 2011, Sebastian Andrzej Siewior wrote:

> * Alan Stern | 2011-03-18 21:27:15 [-0400]:
> 
> >On Fri, 18 Mar 2011, Paul Zimmerman wrote:
> >
> >> > --- a/drivers/usb/gadget/audio.c
> >> > +++ b/drivers/usb/gadget/audio.c
> >> > @@ -52,7 +52,7 @@ static struct usb_device_descriptor device_desc = {
> >> >  	.bLength =		sizeof device_desc,
> >> >  	.bDescriptorType =	USB_DT_DEVICE,
> >> >  
> >> > -	.bcdUSB =		__constant_cpu_to_le16(0x200),
> >> > +	.bcdUSB =		cpu_to_le16(0x0300),
> >> >  
> >> >  	.bDeviceClass =		USB_CLASS_PER_INTERFACE,
> >> >  	.bDeviceSubClass =	0,
> >> 
> >> This won't work. Now the gadget will not be recognized by a USB 2.0
> >> host.
> >
> >Why not?  I'm not aware of any hosts that will refuse to work with a 
> >device merely because the bcdUSB field says 0x0300 instead of 0x0200.
> 
> Quote from ch 9.2.6.6:
> |Devices with a value of at least 0210H in the bcdUSB field of their
> |device descriptor shall support GetDescriptor (BOS Descriptor) requests.
> 
> The device can't handle the GetDescriptor (BOS) yet. I don't know if
> "shall" means "must" or "should".

It does seem premature to change the bcdUSB field until support has 
been added for all the new descriptors.

Alan Stern

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