Re: [PATCH v5] udmabuf: add vmap and vunmap methods to udmabuf_ops

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Pushed this one here to drm-misc-next.

Thanks,
Christian.

Am 17.11.22 um 18:18 schrieb Lukasz Wiecaszek:
The reason behind that patch is associated with videobuf2 subsystem
(or more genrally with v4l2 framework) and user created
dma buffers (udmabuf). In some circumstances
when dealing with V4L2_MEMORY_DMABUF buffers videobuf2 subsystem
wants to use dma_buf_vmap() method on the attached dma buffer.
As udmabuf does not have .vmap operation implemented,
such dma_buf_vmap() natually fails.

videobuf2_common: __vb2_queue_alloc: allocated 3 buffers, 1 plane(s) each
videobuf2_common: __prepare_dmabuf: buffer for plane 0 changed
videobuf2_common: __prepare_dmabuf: failed to map dmabuf for plane 0
videobuf2_common: __buf_prepare: buffer preparation failed: -14

The patch itself seems to be strighforward.
It adds implementation of .vmap and .vunmap methods
to 'struct dma_buf_ops udmabuf_ops'.
.vmap method itself uses vm_map_ram() to map pages linearly
into the kernel virtual address space.
.vunmap removes mapping created earlier by .vmap.
All locking and 'vmapping counting' is done in dma_buf.c
so it seems to be redundant/unnecessary in .vmap/.vunmap.

Reviewed-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
Acked-by: Christian König <christian.koenig@xxxxxxx>
Signed-off-by: Lukasz Wiecaszek <lukasz.wiecaszek@xxxxxxxxx>
---
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v4 -> v5: Added Acked-by and Reviewed-by to the commit message
v3 -> v4: Removed line/info 'reported by kernel test robot'
v2 -> v3: Added .vunmap to 'struct dma_buf_ops udmabuf_ops'
v1 -> v2: Patch prepared and tested against 6.1.0-rc2+

  drivers/dma-buf/udmabuf.c | 28 ++++++++++++++++++++++++++++
  1 file changed, 28 insertions(+)

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index 283816fbd72f..740d6e426ee9 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -13,6 +13,8 @@
  #include <linux/slab.h>
  #include <linux/udmabuf.h>
  #include <linux/hugetlb.h>
+#include <linux/vmalloc.h>
+#include <linux/iosys-map.h>
static int list_limit = 1024;
  module_param(list_limit, int, 0644);
@@ -60,6 +62,30 @@ static int mmap_udmabuf(struct dma_buf *buf, struct vm_area_struct *vma)
  	return 0;
  }
+static int vmap_udmabuf(struct dma_buf *buf, struct iosys_map *map)
+{
+	struct udmabuf *ubuf = buf->priv;
+	void *vaddr;
+
+	dma_resv_assert_held(buf->resv);
+
+	vaddr = vm_map_ram(ubuf->pages, ubuf->pagecount, -1);
+	if (!vaddr)
+		return -EINVAL;
+
+	iosys_map_set_vaddr(map, vaddr);
+	return 0;
+}
+
+static void vunmap_udmabuf(struct dma_buf *buf, struct iosys_map *map)
+{
+	struct udmabuf *ubuf = buf->priv;
+
+	dma_resv_assert_held(buf->resv);
+
+	vm_unmap_ram(map->vaddr, ubuf->pagecount);
+}
+
  static struct sg_table *get_sg_table(struct device *dev, struct dma_buf *buf,
  				     enum dma_data_direction direction)
  {
@@ -162,6 +188,8 @@ static const struct dma_buf_ops udmabuf_ops = {
  	.unmap_dma_buf	   = unmap_udmabuf,
  	.release	   = release_udmabuf,
  	.mmap		   = mmap_udmabuf,
+	.vmap		   = vmap_udmabuf,
+	.vunmap		   = vunmap_udmabuf,
  	.begin_cpu_access  = begin_cpu_udmabuf,
  	.end_cpu_access    = end_cpu_udmabuf,
  };




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