[PATCH] videobuf2-dma-sg: Support io userptr operations on io memory

[Ricardo Ribalda Delgado]

Memory exported via remap_pfn_range cannot be remapped via
get_user_pages.

Other videobuf2 methods (like the dma-contig) supports io memory.

This patch adds support for this kind of memory.

Signed-off-by: Ricardo Ribalda Delgado <ricardo.riba...@gmail.com>
---
 drivers/media/v4l2-core/videobuf2-dma-sg.c | 35 ++++++++++++++++++++++++++----
 1 file changed, 31 insertions(+), 4 deletions(-)

diff --git a/drivers/media/v4l2-core/videobuf2-dma-sg.c 
b/drivers/media/v4l2-core/videobuf2-dma-sg.c
index 2f86054..44ddfe1 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-sg.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-sg.c
@@ -40,6 +40,7 @@ struct vb2_dma_sg_buf {
        unsigned int                    num_pages;
        atomic_t                        refcount;
        struct vb2_vmarea_handler       handler;
+       struct vm_area_struct           *vma;
 };
 
 static void vb2_dma_sg_put(void *buf_priv);
@@ -155,6 +156,11 @@ static void vb2_dma_sg_put(void *buf_priv)
        }
 }
 
+static inline int vma_is_io(struct vm_area_struct *vma)
+{
+       return !!(vma->vm_flags & (VM_IO | VM_PFNMAP));
+}
+
 static void *vb2_dma_sg_get_userptr(void *alloc_ctx, unsigned long vaddr,
                                    unsigned long size, int write)
 {
@@ -180,7 +186,26 @@ static void *vb2_dma_sg_get_userptr(void *alloc_ctx, 
unsigned long vaddr,
        if (!buf->pages)
                return NULL;
 
-       num_pages_from_user = get_user_pages(current, current->mm,
+       buf->vma = find_vma(current->mm, vaddr);
+       if (!buf->vma) {
+               dprintk(1, "no vma for address %lu\n", vaddr);
+               return NULL;
+       }
+
+       if (vma_is_io(buf->vma)) {
+               for (num_pages_from_user = 0;
+                    num_pages_from_user < buf->num_pages;
+                    ++num_pages_from_user, vaddr += PAGE_SIZE) {
+                       unsigned long pfn;
+
+                       if (follow_pfn(buf->vma, vaddr, &pfn)) {
+                               dprintk(1, "no page for address %lu\n", vaddr);
+                               break;
+                       }
+                       buf->pages[num_pages_from_user] = pfn_to_page(pfn);
+               }
+       } else
+               num_pages_from_user = get_user_pages(current, current->mm,
                                             vaddr & PAGE_MASK,
                                             buf->num_pages,
                                             write,
@@ -201,8 +226,9 @@ userptr_fail_alloc_table_from_pages:
 userptr_fail_get_user_pages:
        dprintk(1, "get_user_pages requested/got: %d/%d]\n",
               num_pages_from_user, buf->num_pages);
-       while (--num_pages_from_user >= 0)
-               put_page(buf->pages[num_pages_from_user]);
+       if (!vma_is_io(buf->vma))
+               while (--num_pages_from_user >= 0)
+                       put_page(buf->pages[num_pages_from_user]);
        kfree(buf->pages);
        kfree(buf);
        return NULL;
@@ -225,7 +251,8 @@ static void vb2_dma_sg_put_userptr(void *buf_priv)
        while (--i >= 0) {
                if (buf->write)
                        set_page_dirty_lock(buf->pages[i]);
-               put_page(buf->pages[i]);
+               if (!vma_is_io(buf->vma))
+                       put_page(buf->pages[i]);
        }
        kfree(buf->pages);
        kfree(buf);
-- 
1.8.4.rc3

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