b827e3ac41
The Documentation/DMA-API-HOWTO.txt states that the dma_map_sg() function
returns the number of the created entries in the DMA address space.
However the subsequent calls to the dma_sync_sg_for_{device,cpu}() and
dma_unmap_sg must be called with the original number of the entries
passed to the dma_map_sg().
struct sg_table is a common structure used for describing a non-contiguous
memory buffer, used commonly in the DRM and graphics subsystems. It
consists of a scatterlist with memory pages and DMA addresses (sgl entry),
as well as the number of scatterlist entries: CPU pages (orig_nents entry)
and DMA mapped pages (nents entry).
It turned out that it was a common mistake to misuse nents and orig_nents
entries, calling DMA-mapping functions with a wrong number of entries or
ignoring the number of mapped entries returned by the dma_map_sg()
function.
This driver creatively uses sg_table->orig_nents to store the size of the
allocated scatterlist and ignores the number of the entries returned by
dma_map_sg function. The sg_table->orig_nents is (mis)used to properly
free the (over)allocated scatterlist.
This patch only introduces the common DMA-mapping wrappers operating
directly on the struct sg_table objects to the dmabuf related functions,
so the other drivers, which might share buffers with i915 could rely on
the properly set nents and orig_nents values.
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
128 lines
2.5 KiB
C
128 lines
2.5 KiB
C
/*
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* SPDX-License-Identifier: MIT
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*
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* Copyright © 2016 Intel Corporation
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*/
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#include "mock_dmabuf.h"
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static struct sg_table *mock_map_dma_buf(struct dma_buf_attachment *attachment,
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enum dma_data_direction dir)
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{
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struct mock_dmabuf *mock = to_mock(attachment->dmabuf);
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struct sg_table *st;
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struct scatterlist *sg;
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int i, err;
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st = kmalloc(sizeof(*st), GFP_KERNEL);
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if (!st)
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return ERR_PTR(-ENOMEM);
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err = sg_alloc_table(st, mock->npages, GFP_KERNEL);
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if (err)
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goto err_free;
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sg = st->sgl;
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for (i = 0; i < mock->npages; i++) {
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sg_set_page(sg, mock->pages[i], PAGE_SIZE, 0);
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sg = sg_next(sg);
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}
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err = dma_map_sgtable(attachment->dev, st, dir, 0);
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if (err)
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goto err_st;
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return st;
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err_st:
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sg_free_table(st);
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err_free:
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kfree(st);
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return ERR_PTR(err);
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}
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static void mock_unmap_dma_buf(struct dma_buf_attachment *attachment,
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struct sg_table *st,
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enum dma_data_direction dir)
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{
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dma_unmap_sgtable(attachment->dev, st, dir, 0);
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sg_free_table(st);
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kfree(st);
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}
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static void mock_dmabuf_release(struct dma_buf *dma_buf)
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{
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struct mock_dmabuf *mock = to_mock(dma_buf);
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int i;
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for (i = 0; i < mock->npages; i++)
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put_page(mock->pages[i]);
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kfree(mock);
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}
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static void *mock_dmabuf_vmap(struct dma_buf *dma_buf)
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{
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struct mock_dmabuf *mock = to_mock(dma_buf);
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return vm_map_ram(mock->pages, mock->npages, 0);
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}
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static void mock_dmabuf_vunmap(struct dma_buf *dma_buf, void *vaddr)
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{
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struct mock_dmabuf *mock = to_mock(dma_buf);
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vm_unmap_ram(vaddr, mock->npages);
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}
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static int mock_dmabuf_mmap(struct dma_buf *dma_buf, struct vm_area_struct *vma)
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{
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return -ENODEV;
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}
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static const struct dma_buf_ops mock_dmabuf_ops = {
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.map_dma_buf = mock_map_dma_buf,
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.unmap_dma_buf = mock_unmap_dma_buf,
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.release = mock_dmabuf_release,
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.mmap = mock_dmabuf_mmap,
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.vmap = mock_dmabuf_vmap,
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.vunmap = mock_dmabuf_vunmap,
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};
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static struct dma_buf *mock_dmabuf(int npages)
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{
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struct mock_dmabuf *mock;
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DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
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struct dma_buf *dmabuf;
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int i;
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mock = kmalloc(sizeof(*mock) + npages * sizeof(struct page *),
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GFP_KERNEL);
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if (!mock)
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return ERR_PTR(-ENOMEM);
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mock->npages = npages;
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for (i = 0; i < npages; i++) {
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mock->pages[i] = alloc_page(GFP_KERNEL);
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if (!mock->pages[i])
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goto err;
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}
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exp_info.ops = &mock_dmabuf_ops;
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exp_info.size = npages * PAGE_SIZE;
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exp_info.flags = O_CLOEXEC;
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exp_info.priv = mock;
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dmabuf = dma_buf_export(&exp_info);
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if (IS_ERR(dmabuf))
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goto err;
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return dmabuf;
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err:
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while (i--)
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put_page(mock->pages[i]);
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kfree(mock);
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return ERR_PTR(-ENOMEM);
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}
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