On Tue, 9 Jun 2015 10:16:23 -0400
Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> On Tue, 9 Jun 2015, Li Jun wrote:
>
> > > > -/* USB_DT_OTG (from OTG 1.0a supplement) */
> > > > +/* USB_DT_OTG */
> > > > struct usb_otg_descriptor {
> > > > __u8 bLength;
> > > > __u8 bDescriptorType;
> > > >
> > > > __u8 bmAttributes; /* support for HNP, SRP, etc */
> > > > + struct bcdOTG otg_rev[0];
> > >
> > > why not just __le16 bcdOTG here ?
> >
> > usb_otg_descriptor of OTG 1.0 and 2.0 have different size, if directly add
> > __le16 bcdOTG here, then it cannot used for OTG 1.0.
> > I use a zero length array as Peter suggested here for bcdOTG, then the size
> > of usb_otg_descriptor is still 3(not 5), which is compliant with OTG 1.x, if OTG
where does the memory for the zero length array pointer get allocated then?
> > 2.0 or later, we can use member of otg_rev to add bcdOTG, then the size
> > of usb_otg_descriptor + bcdOTG will be 5, in one word, I want to use existing
> > usb_otg_descriptor struct to cover both OTG 1.x and 2.0
>
> In the end, you may find it is simpler to use two different
> structures: usb_otg_descriptor and usb_otg_20_descriptor.
> Try it and see.
>
cheers,
-roger
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