On 11/15/22 23:04, Lukasz Wiecaszek wrote: > 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. > > Signed-off-by: Lukasz Wiecaszek <[email protected]> > Reported-by: kernel test robot <[email protected]> > --- > v1: > https://lore.kernel.org/linux-media/[email protected]/T/#t > v2: > https://lore.kernel.org/linux-media/20221114052944.GA7264@thinkpad-p72/T/#t > > 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, > };
Reviewed-by: Dmitry Osipenko <[email protected]> -- Best regards, Dmitry
