Commit 89d8589c authored by Tvrtko Ursulin's avatar Tvrtko Ursulin
Browse files

lib/scatterlist: Introduce and export __sg_alloc_table_from_pages 



Drivers like i915 benefit from being able to control the maxium
size of the sg coalesced segment while building the scatter-
gather list.

Introduce and export the __sg_alloc_table_from_pages function
which will allow it that control.

v2: Reorder parameters. (Chris Wilson)
v3: Fix incomplete reordering in v2.
v4: max_segment needs to be page aligned.
v5: Rebase.
v6: Rebase.
v7: Fix spelling in commit and mention max segment size in
    __sg_alloc_table_from_pages kerneldoc. (Andrew Morton)

Signed-off-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: linux-kernel@vger.kernel.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20170803091351.23594-1-tvrtko.ursulin@linux.intel.com
parent c125906b

include/linux/scatterlist.h

+7 −4
Original line number Diff line number Diff line
@@ -267,10 +267,13 @@ void sg_free_table(struct sg_table *); 
int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int,

		     struct scatterlist *, 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 int offset, unsigned long size,

int __sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,

				unsigned int n_pages, unsigned int offset,

				unsigned long size, unsigned int max_segment,

				gfp_t gfp_mask);

int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,

			      unsigned int n_pages, unsigned int offset,

			      unsigned long size, gfp_t gfp_mask);



size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,

		      size_t buflen, off_t skip, bool to_buffer);

lib/scatterlist.c

+49 −17
Original line number Diff line number Diff line
@@ -370,35 +370,38 @@ 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

 * __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)

 * @max_segment: Maximum size of a scatterlist node in bytes (page aligned)

 * @gfp_mask:	 GFP allocation mask

 *

 *  Description:

 *    Allocate and initialize an sg table from a list of pages. Contiguous

 *    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.

 *    ranges of the pages are squashed into a single scatterlist node up to the

 *    maximum size specified in @max_segment. An 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 int offset, unsigned long size,

int __sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,

				unsigned int n_pages, unsigned int offset,

				unsigned long size, unsigned int max_segment,

				gfp_t gfp_mask)

{

	const unsigned int max_segment = SCATTERLIST_MAX_SEGMENT;

	unsigned int chunks, cur_page, seg_len, i;

	int ret;

	struct scatterlist *s;



	if (WARN_ON(!max_segment || offset_in_page(max_segment)))

		return -EINVAL;



	/* compute number of contiguous chunks */

	chunks = 1;

	seg_len = 0;
@@ -440,6 +443,35 @@ int sg_alloc_table_from_pages(struct sg_table *sgt, 


	return 0;

}

EXPORT_SYMBOL(__sg_alloc_table_from_pages);



/**

 * 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. Contiguous

 *    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 int offset,

			      unsigned long size, gfp_t gfp_mask)

{

	return __sg_alloc_table_from_pages(sgt, pages, n_pages, offset, size,

					   SCATTERLIST_MAX_SEGMENT, gfp_mask);

}

EXPORT_SYMBOL(sg_alloc_table_from_pages);



void __sg_page_iter_start(struct sg_page_iter *piter,

CRA Git | Maintained and supported by SUSTech CRA and CCSE