From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-pa0-f46.google.com ([209.85.220.46]:38342 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753717AbbA0I0P (ORCPT ); Tue, 27 Jan 2015 03:26:15 -0500 Received: by mail-pa0-f46.google.com with SMTP id lj1so17098488pab.5 for ; Tue, 27 Jan 2015 00:26:15 -0800 (PST) From: Sumit Semwal To: linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org Cc: linaro-kernel@lists.linaro.org, robdclark@gmail.com, daniel@ffwll.ch, m.szyprowski@samsung.com, stanislawski.tomasz@googlemail.com, robin.murphy@arm.com, Sumit Semwal Subject: [RFCv3 1/2] device: add dma_params->max_segment_count Date: Tue, 27 Jan 2015 13:55:53 +0530 Message-Id: <1422347154-15258-1-git-send-email-sumit.semwal@linaro.org> Sender: linux-media-owner@vger.kernel.org List-ID: From: Rob Clark For devices which have constraints about maximum number of segments in an sglist. For example, a device which could only deal with contiguous buffers would set max_segment_count to 1. The initial motivation is for devices sharing buffers via dma-buf, to allow the buffer exporter to know the constraints of other devices which have attached to the buffer. The dma_mask and fields in 'struct device_dma_parameters' tell the exporter everything else that is needed, except whether the importer has constraints about maximum number of segments. Signed-off-by: Rob Clark [sumits: Minor updates wrt comments] Signed-off-by: Sumit Semwal --- v3: include Robin Murphy's fix[1] for handling '0' as a value for max_segment_count v2: minor updates wrt comments on the first version [1]: http://article.gmane.org/gmane.linux.kernel.iommu/8175/ include/linux/device.h | 1 + include/linux/dma-mapping.h | 19 +++++++++++++++++++ 2 files changed, 20 insertions(+) diff --git a/include/linux/device.h b/include/linux/device.h index fb506738f7b7..a32f9b67315c 100644 --- a/include/linux/device.h +++ b/include/linux/device.h @@ -647,6 +647,7 @@ struct device_dma_parameters { * sg limitations. */ unsigned int max_segment_size; + unsigned int max_segment_count; /* INT_MAX for unlimited */ unsigned long segment_boundary_mask; }; diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index c3007cb4bfa6..d3351a36d5ec 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -154,6 +154,25 @@ static inline unsigned int dma_set_max_seg_size(struct device *dev, return -EIO; } +#define DMA_SEGMENTS_MAX_SEG_COUNT ((unsigned int) INT_MAX) + +static inline unsigned int dma_get_max_seg_count(struct device *dev) +{ + if (dev->dma_parms && dev->dma_parms->max_segment_count) + return dev->dma_parms->max_segment_count; + return DMA_SEGMENTS_MAX_SEG_COUNT; +} + +static inline int dma_set_max_seg_count(struct device *dev, + unsigned int count) +{ + if (dev->dma_parms) { + dev->dma_parms->max_segment_count = count; + return 0; + } + return -EIO; +} + static inline unsigned long dma_get_seg_boundary(struct device *dev) { return dev->dma_parms ? -- 1.9.1