Subject: Re: [RFC 1/2] PCI-Express Non-Transparent Bridge Support

From: Greg KH <[email-masked]>
Date: Sun, 15 Jul 2012 16:53:30 -0700

On Sun, Jul 15, 2012 at 04:50:41PM -0700, Jon Mason wrote:
> On Sat, Jul 14, 2012 at 10:04:11AM -0700, Greg KH wrote:
> > On Fri, Jul 13, 2012 at 02:44:59PM -0700, Jon Mason wrote:
> > > The NTB device driver is needed to configure these memory windows, doorbell, and
> > > scratch-pad registers as well as use them in such a way as they can be turned
> > > into a viable communication channel to the remote system.  ntb_hw.[ch]
> > > determines the usage model (NTB to NTB or NTB to Root Port) and abstracts away
> > > the underlying hardware to provide access and a common interface to the doorbell
> > > registers, scratch pads, and memory windows.  These hardware interfaces are
> > > exported so that other, non-mainlined kernel drivers can access these.
> > 
> > Why would you have non-mainlined drivers?
> > 
> > Can you submit the drivers at the same time so we see how you are using
> > these new interfaces?
> 
> There are none at this time.  In the near future, the transport will
> be modified to use IOAT instead of the CPU copy to improve throughput
> performance, and it may be beneficial to have that separate.  If you
> wish for me to remove the hooks until it is necessary for that, then I
> can.

Yes, please do so, we don't add apis for things that are not in-kernel
as they almost always need to change once we actually get a user of
them, as you know.

thanks,

greg k-h