On 03/08/2017 00:01, Andrew Morton wrote:
On Wed, 2 Aug 2017 14:06:39 +0100 Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx> wrote:
Hi Andrew,
We have a couple of small lib/scatterlist.c tidies here, plus exporting
the new API which allows drivers to control the maximum coalesced entry
as created by __sg_alloc_table_from_pages.
I am looking for an ack to merge these three patches via the drm-intel tree.
...
On 27/07/2017 10:05, Tvrtko Ursulin wrote:
From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Drivers like i915 benefit from being able to control the maxium
size of the sg coallesced segment while building the scatter-
"coalesced"
Oops, I've had this in other patches in the series. Fixed now.
gather list.
Introduce and export the __sg_alloc_table_from_pages function
which will allow it that control.
...
--- 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
The Description doesn't describe how this differs from
sg_alloc_table_from_pages(), although it doesn't seem terribly
important.
Well spotted, I've fixed this as well.
+
+/**
+ * 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);
+}
Making this an inline would save a bunch or stack space in the callers?
One could just add the new arg then run around and update the 10ish
callers but I guess the new interface is OK.
On the first suggestion - there are other trivial wrappers in
lib/scatterlist.c which could benefit from the same treatment (move to
inline) so I opted not to do this in this patch but will send a follow up.
Otherwise it's OK by me, please go ahead as proposed.
Thanks a lot!
Regards,
Tvrtko
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