From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756536AbYA3FwU (ORCPT ); Wed, 30 Jan 2008 00:52:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754112AbYA3FwI (ORCPT ); Wed, 30 Jan 2008 00:52:08 -0500 Received: from relay1.sgi.com ([192.48.171.29]:47189 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753799AbYA3FwG (ORCPT ); Wed, 30 Jan 2008 00:52:06 -0500 From: akepner@sgi.com Date: Tue, 29 Jan 2008 21:50:40 -0800 To: Tony Luck , Grant Grundler , Jesse Barnes , Jes Sorensen , Randy Dunlap , Roland Dreier , James Bottomley , David Miller , Muli Ben-Yehuda Cc: linux-kernel@vger.kernel.org Subject: [PATCH 1/4] dma: document dma_{un}map_{single|sg}_attrs() interface Message-ID: <20080130055040.GS30022@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Document the new dma_{un}map_{single|sg}_attrs() functions. Signed-off-by: Arthur Kepner -- DMA-API.txt | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 63 insertions(+) diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt index b939ebb..fad05e0 100644 --- a/Documentation/DMA-API.txt +++ b/Documentation/DMA-API.txt @@ -395,6 +395,69 @@ Notes: You must do this: See also dma_map_single(). +dma_addr_t +dma_map_single_attrs(struct device *dev, void *cpu_addr, size_t size, + enum dma_data_direction dir, + struct dma_attrs* attrs) + +void +dma_unmap_single_attrs(struct device *dev, dma_addr_t dma_addr, + size_t size, enum dma_data_direction dir, + struct dma_attrs* attrs) + +int +dma_map_sg_attrs(struct device *dev, struct scatterlist *sgl, + int nents, enum dma_data_direction dir, + struct dma_attrs *attrs) + +void +dma_unmap_sg_attrs(struct device *dev, struct scatterlist *sgl, + int nents, enum dma_data_direction dir, + struct dma_attrs *attrs) + +The four functions above are just like the counterpart functions +without the _attrs suffixes, except that they pass an optional +struct dma_attrs*. + +struct dma_attrs encapsulates a set of "dma attributes". For the +definition of struct dma_attrs see linux/dma-attrs.h. + +The interpretation of dma attributes is architecture-specific. + +If struct dma_attrs* is NULL, the semantics of each of these +functions is identical to those of the corresponding function +without the _attrs suffix. As a result dma_map_single_attrs() +can generally replace dma_map_single(), etc. + +As an example of the use of the *_attrs functions, here's how +you could pass an attribute DMA_ATTR_FOO when mapping memory +for DMA: + +#include +/* DMA_ATTR_FOO should be defined in linux/dma-attrs.h */ +... + + DECLARE_DMA_ATTRS(attrs); + dma_set_attr(&attrs, DMA_ATTR_FOO); + .... + n = dma_map_sg_attrs(dev, sg, nents, DMA_TO_DEVICE, &attr); + .... + +Architectures that care about DMA_ATTR_FOO would check for its +presence in their implementations of the mapping and unmapping +routines, e.g.: + +void whizco_dma_map_sg_attrs(struct device *dev, dma_addr_t dma_addr, + size_t size, enum dma_data_direction dir, + struct dma_attrs* attrs) +{ + .... + int foo = dma_get_attr(attrs, DMA_ATTR_FOO); + .... + if (foo) + /* twizzle the frobnozzle */ + .... + Part II - Advanced dma_ usage -----------------------------