drivers/gpu/drm/i915/i915_scatterlist.c

Source file repositories/reference/linux-study-clean/drivers/gpu/drm/i915/i915_scatterlist.c

File Facts

System
Linux kernel
Corpus path
drivers/gpu/drm/i915/i915_scatterlist.c
Extension
.c
Size
6163 bytes
Lines
243
Domain
Driver Families
Bucket
drivers/gpu
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

if (offset != prev_end || sg->length >= max_segment) {
			if (st->nents)
				sg = __sg_next(sg);

			sg_dma_address(sg) = region_start + offset;
			GEM_BUG_ON(!IS_ALIGNED(sg_dma_address(sg),
					       page_alignment));
			sg_dma_len(sg) = 0;
			sg->length = 0;
			st->nents++;
		}

		len = min_t(u64, block_size, max_segment - sg->length);
		sg->length += len;
		sg_dma_len(sg) += len;

		offset += len;
		block_size -= len;

		prev_end = offset;
	}

	sg_mark_end(sg);
	i915_sg_trim(st);

	return rsgt;
}

/**
 * i915_rsgt_from_buddy_resource - Create a refcounted sg_table from a struct
 * i915_buddy_block list
 * @res: The struct i915_ttm_buddy_resource.
 * @region_start: An offset to add to the dma addresses of the sg list.
 * @page_alignment: Required page alignment for each sg entry. Power of two.
 *
 * Create a struct sg_table, initializing it from struct i915_buddy_block list,
 * taking a maximum segment length into account, splitting into segments
 * if necessary.
 *
 * Return: A pointer to a kmalloced struct i915_refct_sgts on success, negative
 * error code cast to an error pointer on failure.
 */
struct i915_refct_sgt *i915_rsgt_from_buddy_resource(struct ttm_resource *res,
						     u64 region_start,
						     u32 page_alignment)
{
	struct i915_ttm_buddy_resource *bman_res = to_ttm_buddy_resource(res);
	const u64 size = res->size;
	const u32 max_segment = round_down(UINT_MAX, page_alignment);
	struct gpu_buddy *mm = bman_res->mm;
	struct list_head *blocks = &bman_res->blocks;
	struct gpu_buddy_block *block;
	struct i915_refct_sgt *rsgt;
	struct scatterlist *sg;
	struct sg_table *st;
	resource_size_t prev_end;

	GEM_BUG_ON(list_empty(blocks));
	GEM_BUG_ON(!max_segment);

	rsgt = kmalloc_obj(*rsgt, GFP_KERNEL | __GFP_NOWARN);
	if (!rsgt)
		return ERR_PTR(-ENOMEM);

	i915_refct_sgt_init(rsgt, size);
	st = &rsgt->table;
	/* restricted by sg_alloc_table */
	if (WARN_ON(overflows_type(PFN_UP(res->size), unsigned int))) {
		i915_refct_sgt_put(rsgt);
		return ERR_PTR(-E2BIG);
	}

	if (sg_alloc_table(st, PFN_UP(res->size), GFP_KERNEL | __GFP_NOWARN)) {
		i915_refct_sgt_put(rsgt);
		return ERR_PTR(-ENOMEM);
	}

	sg = st->sgl;
	st->nents = 0;
	prev_end = (resource_size_t)-1;

	list_for_each_entry(block, blocks, link) {
		u64 block_size, offset;

		block_size = min_t(u64, size, gpu_buddy_block_size(mm, block));
		offset = gpu_buddy_block_offset(block);

		while (block_size) {
			u64 len;

Annotation

Implementation Notes