Re: [Xen-devel] [PATCH RFC 1/2] usbif.h: don't require PAGE_SIZE to be present

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 19 Oct 2016, David Vrabel wrote:
> On 19/10/16 11:46, Wei Liu wrote:
> > If it is present, use it; otherwise use 4096. Also provide two new
> > macros to let user have control over the page size used to do
> > calculation.
> [...]
> > index 4053c24..ac38318 100644
> > --- a/xen/include/public/io/usbif.h
> > +++ b/xen/include/public/io/usbif.h
> > @@ -216,6 +216,16 @@ struct usbif_urb_request {
> >  };
> >  typedef struct usbif_urb_request usbif_urb_request_t;
> >  
> > +/*
> > + * Reference to PAGE_SIZE was overlooked when this header file was
> > + * introduced. Respect PAGE_SIZE if defined, otherwise, use 4096.
> > + */
> > +#ifdef PAGE_SIZE
> > +#define _USB_RING_PAGE_SIZE PAGE_SIZE
> 
> #define XEN_USBIF_RING_SIZE 4096
> 
> Since PAGE_SIZE on the backend is not necessarily PAGE_SIZE in the
> frontend.  This is what the size has always been so it won't break anything.
> 
> And similarly for vscsiif.

That is exactly right, thank you.

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