From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart Van Assche Subject: Re: [PATCH 2/9] Move dma_ops from archdata into struct device Date: Wed, 11 Jan 2017 18:17:03 +0000 Message-ID: <1484158589.2619.14.camel@sandisk.com> References: <20170111005648.14988-1-bart.vanassche@sandisk.com> <20170111005648.14988-3-bart.vanassche@sandisk.com> <20170111064803.GB26893@kroah.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sandiskcorp.onmicrosoft.com; s=selector1-sandisk-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version; bh=NY+kQeXZdTCL+o+TxsBWYVyK8kK/EXRi4NmCLqVhEII=; b=pskBxsC6n4NDYtLFPd4ZJQoaAWUBjsQH1b9ZXj93CPiiOLleK1efiydJ2M2DPFOstsgOqKwulHMzc/Te3+oik9QIulgUDQe+jc/SMcn+eydqAaW+AVQ7Mh6E6/SUUmRqZSmI3Q4JhVqejmY5ekjYMGhr7kNPi8BEX8m3asu62WU= In-Reply-To: <20170111064803.GB26893-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org> Content-Language: en-US Content-ID: List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: "gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org" Cc: "linux-mips-6z/3iImG2C8G8FEW9MqTrA@public.gmane.org" , "dalias-8zAoT0mYgF4@public.gmane.org" , "linux-ia64-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "a-jacquiot-l0cyMroinI0@public.gmane.org" , "catalin.marinas-5wv7dgnIgG8@public.gmane.org" , "will.deacon-5wv7dgnIgG8@public.gmane.org" , "x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org" , "mulix-BzGcCpaT2IbYtjvyW6yDsg@public.gmane.org" , "dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org" , "jcmvbkbc-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org" , "hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org" , "sparclinux-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org" , "egtvedt-BrfabpQBY5qlHtIdYg32fQ@public.gmane.org" , "jonas-A9uVI2HLR7kOP4wsBPIw7w@public.gmane.org" , "linux-s390-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "jesper.nilsson-VrBV9hrLPhE@public.gmane.org" , "linux-am33-list-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org" , "linux-c6x-dev-jPsnJVOj+W6hPH1hqNUYSQ@public.gmane.org" On Wed, 2017-01-11 at 07:48 +0100, Greg Kroah-Hartman wrote: > On Tue, Jan 10, 2017 at 04:56:41PM -0800, Bart Van Assche wrote: > > Several RDMA drivers, e.g. drivers/infiniband/hw/qib, use the CPU to > > transfer data between memory and PCIe adapter. Because of performance > > reasons it is important that the CPU cache is not flushed when such > > drivers transfer data. Make this possible by allowing these drivers to > > override the dma_map_ops pointer. Additionally, introduce the function > > set_dma_ops() that will be used by a later patch in this series. > = > When you say things like "additionally", that's a huge flag that this > needs to be split up into multiple patches.=A0=A0No need to add > set_dma_ops() here in this patch. Hello Greg, Some architectures already define a=A0set_dma_ops() function. So what this patch does is to move both the dma_ops pointer and the set_dma_ops() function from architecture-specific to architecture independent code. I don't think that it is possible to separate these two changes. But I understand that how I formulated the patch description caused confusion. I will rewrite the patch description to make it more clear before I repost this patch series. > And I'd argue that it should be dma_ops_set(), and dma_ops_get(), just > to keep the namespace sane, but that's probably a different set of > patches... Every time I rebase and retest this patch series on top of a new kernel version I have to modify some of the patches to compensate for changes in the architecture code. So I expect that once Linus merges these patches that he will have to resolve one or more merge conflicts. Including a rename of the functions that query and set the dma_ops pointer in this patch series would increase the number of merge conflicts triggered by this patch series and would make Linus' job harder. So I hope that you will allow me to postpone that rename until a later time ... Bart.