[media] v4l: vb2: add support for shared buffer (dma_buf)

This patch adds support for DMABUF memory type in videobuf2. It calls relevant
APIs of dma_buf for v4l reqbuf / qbuf / dqbuf operations.
For this version, the support is for videobuf2 as a user of the shared buffer;
so the allocation of the buffer is done outside of V4L2. [A sample allocator of
dma-buf shared buffer is given at [1]]
[1]: Rob Clark's DRM:
   https://github.com/robclark/kernel-omap4/commits/drmplane-dmabuf
   [original work in the PoC for buffer sharing]

Signed-off-by: Tomasz Stanislawski <t.stanislaws@samsung.com>
Signed-off-by: Sumit Semwal <sumit.semwal@ti.com>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Tested-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index e04252a9fea6..689ae4ac2572 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -16,6 +16,7 @@
 #include <linux/mutex.h>
 #include <linux/poll.h>
 #include <linux/videodev2.h>
+#include <linux/dma-buf.h>
 
 struct vb2_alloc_ctx;
 struct vb2_fileio_data;
@@ -41,6 +42,20 @@ struct vb2_fileio_data;
  *               argument to other ops in this structure
  * @put_userptr: inform the allocator that a USERPTR buffer will no longer
  *               be used
+ * @attach_dmabuf: attach a shared struct dma_buf for a hardware operation;
+ *                 used for DMABUF memory types; alloc_ctx is the alloc context
+ *                 dbuf is the shared dma_buf; returns NULL on failure;
+ *                 allocator private per-buffer structure on success;
+ *                 this needs to be used for further accesses to the buffer
+ * @detach_dmabuf: inform the exporter of the buffer that the current DMABUF
+ *                 buffer is no longer used; the buf_priv argument is the
+ *                 allocator private per-buffer structure previously returned
+ *                 from the attach_dmabuf callback
+ * @map_dmabuf: request for access to the dmabuf from allocator; the allocator
+ *              of dmabuf is informed that this driver is going to use the
+ *              dmabuf
+ * @unmap_dmabuf: releases access control to the dmabuf - allocator is notified
+ *                that this driver is done using the dmabuf for now
  * @vaddr:      return a kernel virtual address to a given memory buffer
  *              associated with the passed private structure or NULL if no
  *              such mapping exists
@@ -56,6 +71,8 @@ struct vb2_fileio_data;
  * Required ops for USERPTR types: get_userptr, put_userptr.
  * Required ops for MMAP types: alloc, put, num_users, mmap.
  * Required ops for read/write access types: alloc, put, num_users, vaddr
+ * Required ops for DMABUF types: attach_dmabuf, detach_dmabuf, map_dmabuf,
+ *                                unmap_dmabuf.
  */
 struct vb2_mem_ops {
         void            *(*alloc)(void *alloc_ctx, unsigned long size);
@@ -65,6 +82,12 @@ struct vb2_mem_ops {
                                         unsigned long size, int write);
         void            (*put_userptr)(void *buf_priv);
 
+        void            *(*attach_dmabuf)(void *alloc_ctx, struct dma_buf *dbuf,
+                                unsigned long size, int write);
+        void            (*detach_dmabuf)(void *buf_priv);
+        int             (*map_dmabuf)(void *buf_priv);
+        void            (*unmap_dmabuf)(void *buf_priv);
+
         void            *(*vaddr)(void *buf_priv);
         void            *(*cookie)(void *buf_priv);
 
@@ -75,6 +98,8 @@ struct vb2_mem_ops {
 
 struct vb2_plane {
         void                    *mem_priv;
+        struct dma_buf          *dbuf;
+        unsigned int            dbuf_mapped;
 };
 
 /**
@@ -83,12 +108,14 @@ struct vb2_plane {
  * @VB2_USERPTR:        driver supports USERPTR with streaming API
  * @VB2_READ:           driver supports read() style access
  * @VB2_WRITE:          driver supports write() style access
+ * @VB2_DMABUF:         driver supports DMABUF with streaming API
  */
 enum vb2_io_modes {
         VB2_MMAP        = (1 << 0),
         VB2_USERPTR     = (1 << 1),
         VB2_READ        = (1 << 2),
         VB2_WRITE       = (1 << 3),
+        VB2_DMABUF      = (1 << 4),
 };
 
 /**