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Date: Wed, 11 Jan 2017 09:00:37 +0000
From: Tvrtko Ursulin <tursulin@...ulin.net>
To: Intel-gfx@...ts.freedesktop.org
Cc: tursulin@...ulin.net, Tvrtko Ursulin <tvrtko.ursulin@...el.com>,
Masahiro Yamada <yamada.masahiro@...ionext.com>,
linux-kernel@...r.kernel.org,
Chris Wilson <chris@...is-wilson.co.uk>
Subject: [PATCH 3/4] lib/scatterlist: Introduce and export __sg_alloc_table_from_pages
From: Tvrtko Ursulin <tvrtko.ursulin@...el.com>
Drivers like i915 benefit from being able to control the maxium
size of the sg coallesced 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.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@...el.com>
Cc: Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc: linux-kernel@...r.kernel.org
Cc: Chris Wilson <chris@...is-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@...is-wilson.co.uk> (v2)
---
include/linux/scatterlist.h | 11 ++++++---
lib/scatterlist.c | 59 +++++++++++++++++++++++++++++++++++----------
2 files changed, 53 insertions(+), 17 deletions(-)
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index c981bee1a3ae..16b740afeed2 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -261,10 +261,13 @@ 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,
- 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, 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);
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 4fc54801cd29..df375ff18587 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -370,14 +370,15 @@ 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
+ * __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
@@ -389,18 +390,20 @@ EXPORT_SYMBOL(sg_alloc_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)
+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 = rounddown(UINT_MAX, PAGE_SIZE);
unsigned int seg_len, chunks;
unsigned int i;
unsigned int cur_page;
int ret;
struct scatterlist *s;
+ if (WARN_ON(offset_in_page(max_segment)))
+ return -EINVAL;
+
/* compute number of contiguous chunks */
chunks = 1;
seg_len = PAGE_SIZE;
@@ -444,6 +447,36 @@ 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,
+ rounddown(UINT_MAX, PAGE_SIZE),
+ gfp_mask);
+}
EXPORT_SYMBOL(sg_alloc_table_from_pages);
void __sg_page_iter_start(struct sg_page_iter *piter,
--
2.7.4
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