Em Fri, 08 May 2009 17:53:10 +0900
Magnus Damm <magnus.damm@xxxxxxxxx> escreveu:
> From: Magnus Damm <damm@xxxxxxxxxx>
>
> This is V3 of the V4L2 videobuf-dma-contig USERPTR zero copy patch.
>
> Since videobuf-dma-contig is designed to handle physically contiguous
> memory, this patch modifies the videobuf-dma-contig code to only accept
> a user space pointer to physically contiguous memory. For now only
> VM_PFNMAP vmas are supported, so forget hotplug.
>
> On SuperH Mobile we use this with our sh_mobile_ceu_camera driver
> together with various multimedia accelerator blocks that are exported to
> user space using UIO. The UIO kernel code exports physically contiguous
> memory to user space and lets the user space application mmap() this memory
> and pass a pointer using the USERPTR interface for V4L2 zero copy operation.
>
> With this approach we support zero copy capture, hardware scaling and
> various forms of hardware encoding and decoding.
>
> Signed-off-by: Magnus Damm <damm@xxxxxxxxxx>
Acked-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
> ---
>
> Needs the following patches (Thanks to Johannes Weiner and akpm):
> - mm-introduce-follow_pte.patch
> - mm-use-generic-follow_pte-in-follow_phys.patch
> - mm-introduce-follow_pfn.patch
>
> Tested on SH7722 Migo-R with a hacked up capture.c
>
> Changes since V2:
> - use follow_pfn(), drop mm/memory.c changes
>
> Changes since V1:
> - minor cleanups and formatting changes
> - use follow_phys() in videobuf-dma-contig instead of duplicating code
> - since videobuf-dma-contig can be a module: EXPORT_SYMBOL(follow_phys)
> - move CONFIG_HAVE_IOREMAP_PROT to always build follow_phys()
>
> drivers/media/video/videobuf-dma-contig.c | 78 +++++++++++++++++++++++++++--
> 1 file changed, 73 insertions(+), 5 deletions(-)
>
> --- 0013/drivers/media/video/videobuf-dma-contig.c
> +++ work/drivers/media/video/videobuf-dma-contig.c 2009-05-08 15:57:21.000000000 +0900
> @@ -17,6 +17,7 @@
> #include <linux/init.h>
> #include <linux/module.h>
> #include <linux/mm.h>
> +#include <linux/pagemap.h>
> #include <linux/dma-mapping.h>
> #include <media/videobuf-dma-contig.h>
>
> @@ -25,6 +26,7 @@ struct videobuf_dma_contig_memory {
> void *vaddr;
> dma_addr_t dma_handle;
> unsigned long size;
> + int is_userptr;
> };
>
> #define MAGIC_DC_MEM 0x0733ac61
> @@ -108,6 +110,66 @@ static struct vm_operations_struct video
> .close = videobuf_vm_close,
> };
>
> +static void videobuf_dma_contig_user_put(struct videobuf_dma_contig_memory *mem)
> +{
> + mem->is_userptr = 0;
> + mem->dma_handle = 0;
> + mem->size = 0;
> +}
> +
> +static int videobuf_dma_contig_user_get(struct videobuf_dma_contig_memory *mem,
> + struct videobuf_buffer *vb)
> +{
> + struct mm_struct *mm = current->mm;
> + struct vm_area_struct *vma;
> + unsigned long prev_pfn, this_pfn;
> + unsigned long pages_done, user_address;
> + int ret;
> +
> + mem->size = PAGE_ALIGN(vb->size);
> + mem->is_userptr = 0;
> + ret = -EINVAL;
> +
> + down_read(&mm->mmap_sem);
> +
> + vma = find_vma(mm, vb->baddr);
> + if (!vma)
> + goto out_up;
> +
> + if ((vb->baddr + mem->size) > vma->vm_end)
> + goto out_up;
> +
> + pages_done = 0;
> + prev_pfn = 0; /* kill warning */
> + user_address = vb->baddr;
> +
> + while (pages_done < (mem->size >> PAGE_SHIFT)) {
> + ret = follow_pfn(vma, user_address, &this_pfn);
> + if (ret)
> + break;
> +
> + if (pages_done == 0)
> + mem->dma_handle = this_pfn << PAGE_SHIFT;
> + else if (this_pfn != (prev_pfn + 1))
> + ret = -EFAULT;
> +
> + if (ret)
> + break;
> +
> + prev_pfn = this_pfn;
> + user_address += PAGE_SIZE;
> + pages_done++;
> + }
> +
> + if (!ret)
> + mem->is_userptr = 1;
> +
> + out_up:
> + up_read(¤t->mm->mmap_sem);
> +
> + return ret;
> +}
> +
> static void *__videobuf_alloc(size_t size)
> {
> struct videobuf_dma_contig_memory *mem;
> @@ -154,12 +216,11 @@ static int __videobuf_iolock(struct vide
> case V4L2_MEMORY_USERPTR:
> dev_dbg(q->dev, "%s memory method USERPTR\n", __func__);
>
> - /* The only USERPTR currently supported is the one needed for
> - read() method.
> - */
> + /* handle pointer from user space */
> if (vb->baddr)
> - return -EINVAL;
> + return videobuf_dma_contig_user_get(mem, vb);
>
> + /* allocate memory for the read() method */
> mem->size = PAGE_ALIGN(vb->size);
> mem->vaddr = dma_alloc_coherent(q->dev, mem->size,
> &mem->dma_handle, GFP_KERNEL);
> @@ -386,7 +447,7 @@ void videobuf_dma_contig_free(struct vid
> So, it should free memory only if the memory were allocated for
> read() operation.
> */
> - if ((buf->memory != V4L2_MEMORY_USERPTR) || buf->baddr)
> + if (buf->memory != V4L2_MEMORY_USERPTR)
> return;
>
> if (!mem)
> @@ -394,6 +455,13 @@ void videobuf_dma_contig_free(struct vid
>
> MAGIC_CHECK(mem->magic, MAGIC_DC_MEM);
>
> + /* handle user space pointer case */
> + if (buf->baddr) {
> + videobuf_dma_contig_user_put(mem);
> + return;
> + }
> +
> + /* read() method */
> dma_free_coherent(q->dev, mem->size, mem->vaddr, mem->dma_handle);
> mem->vaddr = NULL;
> }
> --
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Cheers,
Mauro
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