From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752800AbaIEV0K (ORCPT ); Fri, 5 Sep 2014 17:26:10 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:42299 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752714AbaIEV0I (ORCPT ); Fri, 5 Sep 2014 17:26:08 -0400 Date: Fri, 5 Sep 2014 14:26:07 -0700 From: Greg KH To: KY Srinivasan Cc: "linux-kernel@vger.kernel.org" , "devel@linuxdriverproject.org" , "olaf@aepfle.de" , "apw@canonical.com" , "jasowang@redhat.com" Subject: Re: [PATCH 1/1] Drivers: hv: vmbus: Enable interrupt driven flow control Message-ID: <20140905212607.GA29137@kroah.com> References: <1409941402-486-1-git-send-email-kys@microsoft.com> <20140905191148.GA24879@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 05, 2014 at 08:53:01PM +0000, KY Srinivasan wrote: > > > > -----Original Message----- > > From: Greg KH [mailto:gregkh@linuxfoundation.org] > > Sent: Friday, September 5, 2014 12:12 PM > > To: KY Srinivasan > > Cc: linux-kernel@vger.kernel.org; devel@linuxdriverproject.org; > > olaf@aepfle.de; apw@canonical.com; jasowang@redhat.com > > Subject: Re: [PATCH 1/1] Drivers: hv: vmbus: Enable interrupt driven flow > > control > > > > On Fri, Sep 05, 2014 at 11:23:22AM -0700, K. Y. Srinivasan wrote: > > > This is a win8 feature that has been implemented. Turn on the feature > > > bit to enable the feature. > > > > What does those two sentances even mean? > Greg, > > The feature has been implemented and has been in the tree for a while. What feature? What is "This" in the first sentance? > However, the feature was not advertised to the host and this patch does just that. > > > > > With this feature turned on, > > > > What is "this"? > "this" refers to the feature bit. > > > > > when the host is waiting > > > for space to become available on the ringbuffer (host to guest), the > > > guest will interrupt the host when space becomes available (as part of > > > draining the ring buffer). > > > > > > Signed-off-by: K. Y. Srinivasan > > > --- > > > drivers/hv/ring_buffer.c | 5 +++++ > > > 1 files changed, 5 insertions(+), 0 deletions(-) > > > > > > diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c index > > > 15db66b..6361d12 100644 > > > --- a/drivers/hv/ring_buffer.c > > > +++ b/drivers/hv/ring_buffer.c > > > @@ -361,6 +361,11 @@ int hv_ringbuffer_init(struct hv_ring_buffer_info > > *ring_info, > > > ring_info->ring_buffer->read_index = > > > ring_info->ring_buffer->write_index = 0; > > > > > > + /* > > > + * Set the feature bit for enabling flow control. > > > + */ > > > + ring_info->ring_buffer->feature_bits.value = 1; > > > > What happens if you are running on an old system that doesn't support this > > new "feature"? > The control structure for the ring buffer (where this feature bit is) has not changed and so, for > hosts that don't understand this, it does not matter. > > Hope this helps. Let me know if you want me to rewrite comment and resend this patch. Please do, it's confusing :) thanks, greg k-h