From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Subject: Re: Kernel fast memory registration API proposal [RFC]
Date: Thu, 16 Jul 2015 01:07:02 -0700
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To: Sagi Grimberg <sagig-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>
Cc: Chuck Lever <chuck.lever-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>, Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>, Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>, "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>, Or Gerlitz <ogerlitz-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>, Oren Duer <oren-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>, Bart Van Assche <bvanassche-HInyCGIudOg@public.gmane.org>, Liran Liss <liranl-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>, "Hefty, Sean" <sean.hefty-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Tom Talpey <tom-CLs1Zie5N5HQT0dZR+AlfA@public.gmane.org>
List-Id: linux-rdma@vger.kernel.org

On Thu, Jul 16, 2015 at 09:52:44AM +0300, Sagi Grimberg wrote:
> >>I suggest to start with what I proposed. And in a later stage (if we
> >>still think its needed) we can have a higher level API that hides the
> >>post, something like:
> >
> >>rdma_reg_sg(struct ib_qp *qp,
> >>            struct ib_mr *mr,
> >>            struct scatterlist *sg,
> >>            int sg_nents,
> >>            u64 offset,
> >>            u64 length,
> >>            int access_flags)
> >
> >I still wonder what ?length? means in the context of a scatterlist.
> 
> Would byte_count be a more explanatory name?

What do you even need it for?  The total length is implicitly stored in
the S/G list as the list of all elements.

What's the offset for?  To allow skipping parts of a S/G list previously
mapped?
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