Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753209Ab2EHLOY (ORCPT ); Tue, 8 May 2012 07:14:24 -0400 Received: from perceval.ideasonboard.com ([95.142.166.194]:35900 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752000Ab2EHLOX (ORCPT ); Tue, 8 May 2012 07:14:23 -0400 From: Laurent Pinchart To: Tomasz Stanislawski 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" , Rob Clark , Dave Airlie , linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] scatterlist: add sg_alloc_table_from_pages function Date: Tue, 08 May 2012 13:14:23 +0200 Message-ID: <1976581.7lABks1hJQ@avalon> User-Agent: KMail/4.8.3 (Linux/3.2.1-gentoo-r2; KDE/4.8.3; x86_64; ; ) In-Reply-To: <4FA8EC69.8010805@samsung.com> References: <4FA8EC69.8010805@samsung.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4624 Lines: 130 Hi Tomasz, Thank you for the patch. On Tuesday 08 May 2012 11:50:33 Tomasz Stanislawski wrote: > 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 perform > conversion from an page array to a scatterlist. Moreover the scatterlist > should be squashed in order to save memory and to speed-up the process of > 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 Acked-by: Laurent Pinchart > --- > include/linux/scatterlist.h | 4 +++ > lib/scatterlist.c | 64 > +++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 68 > insertions(+), 0 deletions(-) > > diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h > index ac9586d..7b600da 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_from_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..85868a1 100644 > --- a/lib/scatterlist.c > +++ b/lib/scatterlist.c > @@ -319,6 +319,70 @@ int sg_alloc_table(struct sg_table *table, unsigned int > nents, gfp_t gfp_mask) EXPORT_SYMBOL(sg_alloc_table); > > /** > + * sg_alloc_table_from_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, negative error on failure > + **/ > +int sg_alloc_table_from_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 (page_to_pfn(pages[i]) != page_to_pfn(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 (page_to_pfn(pages[j]) != > + page_to_pfn(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_from_pages); > + > +/** > * sg_miter_start - start mapping iteration over a sg list > * @miter: sg mapping iter to be started > * @sgl: sg list to iterate over -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/