From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752416Ab2DRJuH (ORCPT ); Wed, 18 Apr 2012 05:50:07 -0400 Received: from plane.gmane.org ([80.91.229.3]:59495 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751518Ab2DRJuF (ORCPT ); Wed, 18 Apr 2012 05:50:05 -0400 X-Injected-Via-Gmane: http://gmane.org/ To: linux-kernel@vger.kernel.org From: Tomasz Stanislawski Subject: [PATCH] scatterlist: add sg_alloc_table_by_pages function Date: Wed, 18 Apr 2012 11:44:59 +0200 Message-ID: <4F8E8D1B.7020901@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Complaints-To: usenet@dough.gmane.org Cc: paul.gortmaker@windriver.com, =?UTF-8?B?J+uwleqyveuvvCc=?= , amwang@redhat.com, dri-devel@lists.freedesktop.org, "'???/Mobile S/W Platform Lab.(???)/E3(??)/????'" , prashanth.g@samsung.com, Marek Szyprowski , "linux-media@vger.kernel.org" , Laurent Pinchart , Rob Clark , Dave Airlie , "'???/Mobile S/W Platform Lab.(???)/E3(??)/????'" X-Gmane-NNTP-Posting-Host: 217-67-201-162.itsa.net.pl User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:11.0) Gecko/20120310 Thunderbird/11.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch adds a new constructor for an sg table. The table is constructed from an array of struct pages. All contiguous chunks of the pages are merged into a single sg nodes. A user may provide an offset and a size of a buffer if the buffer is not page-aligned. The function is dedicated for DMABUF exporters which often performs conversion from an page array to a scatterlist. Moreover the scatterlist should be squashed in order to save memory and to speed-up DMA mapping using dma_map_sg. The code is based on the patch 'v4l: vb2-dma-contig: add support for scatterlist in userptr mode' and hints from Laurent Pinchart. Signed-off-by: Tomasz Stanislawski Signed-off-by: Kyungmin Park --- include/linux/scatterlist.h | 4 +++ lib/scatterlist.c | 63 +++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 67 insertions(+), 0 deletions(-) diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index ac9586d..8d9e6fe 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -214,6 +214,10 @@ void sg_free_table(struct sg_table *); int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int, gfp_t, sg_alloc_fn *); int sg_alloc_table(struct sg_table *, unsigned int, gfp_t); +int sg_alloc_table_by_pages(struct sg_table *sgt, + struct page **pages, unsigned int n_pages, + unsigned long offset, unsigned long size, + gfp_t gfp_mask); size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents, void *buf, size_t buflen); diff --git a/lib/scatterlist.c b/lib/scatterlist.c index 6096e89..30b9def 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -319,6 +319,69 @@ int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask) EXPORT_SYMBOL(sg_alloc_table); /** + * sg_alloc_table_by_pages - Allocate and initialize an sg table from an array + * of pages + * @sgt: The sg table header to use + * @pages: Pointer to an array of page pointers + * @n_pages: Number of pages in the pages array + * @offset: Offset from start of the first page to the start of a buffer + * @size: Number of valid bytes in the buffer (after offset) + * @gfp_mask: GFP allocation mask + * + * Description: + * Allocate and initialize an sg table from a list of pages. Continuous + * ranges of the pages are squashed into a single scatterlist node. A user + * may provide an offset at a start and a size of valid data in a buffer + * specified by the page array. The returned sg table is released by + * sg_free_table. + * + * Returns: + * 0 on success + **/ +int sg_alloc_table_by_pages(struct sg_table *sgt, + struct page **pages, unsigned int n_pages, + unsigned long offset, unsigned long size, + gfp_t gfp_mask) +{ + unsigned int chunks; + unsigned int i; + unsigned int cur_page; + int ret; + struct scatterlist *s; + + /* compute number of contiguous chunks */ + chunks = 1; + for (i = 1; i < n_pages; ++i) + if (pages[i] != pages[i - 1] + 1) + ++chunks; + + ret = sg_alloc_table(sgt, chunks, gfp_mask); + if (unlikely(ret)) + return ret; + + /* merging chunks and putting them into the scatterlist */ + cur_page = 0; + for_each_sg(sgt->sgl, s, sgt->orig_nents, i) { + unsigned long chunk_size; + unsigned int j; + + /* looking for the end of the current chunk */ + for (j = cur_page + 1; j < n_pages; ++j) + if (pages[j] != pages[j - 1] + 1) + break; + + chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset; + sg_set_page(s, pages[cur_page], min(size, chunk_size), offset); + size -= chunk_size; + offset = 0; + cur_page = j; + } + + return 0; +} +EXPORT_SYMBOL(sg_alloc_table_by_pages); + +/** * sg_miter_start - start mapping iteration over a sg list * @miter: sg mapping iter to be started * @sgl: sg list to iterate over -- 1.7.5.4