target/linux/brcm2708/patches-4.19/950-0699-media-vb2-Allow-reqbufs-0-with-in-use-MMAP-buffers.patch

   1 From b0102490b31330eb694a7956e1874e172ad07ec1 Mon Sep 17 00:00:00 2001
   2 From: John Sheu <sheu@chromium.org>
   3 Date: Thu, 15 Nov 2018 10:57:16 -0500
   4 Subject: [PATCH 699/703] media: vb2: Allow reqbufs(0) with "in use" MMAP
   5  buffers
   6
   7 Upstream commit d644cca50f366cd109845ae92e37c09ed79adf81
   8
   9 Videobuf2 presently does not allow VIDIOC_REQBUFS to destroy outstanding
  10 buffers if the queue is of type V4L2_MEMORY_MMAP, and if the buffers are
  11 considered "in use".  This is different behavior than for other memory
  12 types and prevents us from deallocating buffers in following two cases:
  13
  14 1) There are outstanding mmap()ed views on the buffer. However even if
  15    we put the buffer in reqbufs(0), there will be remaining references,
  16    due to vma .open/close() adjusting vb2 buffer refcount appropriately.
  17    This means that the buffer will be in fact freed only when the last
  18    mmap()ed view is unmapped.
  19
  20 2) Buffer has been exported as a DMABUF. Refcount of the vb2 buffer
  21    is managed properly by VB2 DMABUF ops, i.e. incremented on DMABUF
  22    get and decremented on DMABUF release. This means that the buffer
  23    will be alive until all importers release it.
  24
  25 Considering both cases above, there does not seem to be any need to
  26 prevent reqbufs(0) operation, because buffer lifetime is already
  27 properly managed by both mmap() and DMABUF code paths. Let's remove it
  28 and allow userspace freeing the queue (and potentially allocating a new
  29 one) even though old buffers might be still in processing.
  30
  31 To let userspace know that the kernel now supports orphaning buffers
  32 that are still in use, add a new V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS
  33 to be set by reqbufs and create_bufs.
  34
  35 [p.zabel@pengutronix.de: added V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS,
  36  updated documentation, and added back debug message]
  37
  38 Signed-off-by: John Sheu <sheu@chromium.org>
  39 Reviewed-by: Pawel Osciak <posciak@chromium.org>
  40 Signed-off-by: Tomasz Figa <tfiga@chromium.org>
  41 Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
  42 Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
  43 Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
  44 [hverkuil-cisco@xs4all.nl: added V4L2-BUF-CAP-SUPPORTS-ORPHANED-BUFS ref]
  45 Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
  46 ---
  47  Documentation/media/uapi/v4l/vidioc-reqbufs.rst | 17 ++++++++++++++---
  48  drivers/media/common/videobuf2/videobuf2-core.c |  8 +++-----
  49  drivers/media/common/videobuf2/videobuf2-v4l2.c |  2 +-
  50  include/uapi/linux/videodev2.h                  |  1 +
  51  4 files changed, 19 insertions(+), 9 deletions(-)
  52
  53 --- a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
  54 +++ b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
  55 @@ -59,9 +59,14 @@ When the I/O method is not supported the
  56  code.
  57
  58  Applications can call :ref:`VIDIOC_REQBUFS` again to change the number of
  59 -buffers, however this cannot succeed when any buffers are still mapped.
  60 -A ``count`` value of zero frees all buffers, after aborting or finishing
  61 -any DMA in progress, an implicit
  62 +buffers. Note that if any buffers are still mapped or exported via DMABUF,
  63 +then :ref:`VIDIOC_REQBUFS` can only succeed if the
  64 +``V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS`` capability is set. Otherwise
  65 +:ref:`VIDIOC_REQBUFS` will return the ``EBUSY`` error code.
  66 +If ``V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS`` is set, then these buffers are
  67 +orphaned and will be freed when they are unmapped or when the exported DMABUF
  68 +fds are closed. A ``count`` value of zero frees or orphans all buffers, after
  69 +aborting or finishing any DMA in progress, an implicit
  70  :ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>`.
  71
  72
  73 @@ -112,6 +117,7 @@ any DMA in progress, an implicit
  74  .. _V4L2-BUF-CAP-SUPPORTS-USERPTR:
  75  .. _V4L2-BUF-CAP-SUPPORTS-DMABUF:
  76  .. _V4L2-BUF-CAP-SUPPORTS-REQUESTS:
  77 +.. _V4L2-BUF-CAP-SUPPORTS-ORPHANED-BUFS:
  78
  79  .. cssclass:: longtable
  80
  81 @@ -132,6 +138,11 @@ any DMA in progress, an implicit
  82      * - ``V4L2_BUF_CAP_SUPPORTS_REQUESTS``
  83        - 0x00000008
  84        - This buffer type supports :ref:`requests <media-request-api>`.
  85 +    * - ``V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS``
  86 +      - 0x00000010
  87 +      - The kernel allows calling :ref:`VIDIOC_REQBUFS` while buffers are still
  88 +        mapped or exported via DMABUF. These orphaned buffers will be freed
  89 +        when they are unmapped or when the exported DMABUF fds are closed.
  90
  91  Return Value
  92  ============
  93 --- a/drivers/media/common/videobuf2/videobuf2-core.c
  94 +++ b/drivers/media/common/videobuf2/videobuf2-core.c
  95 @@ -684,11 +684,9 @@ int vb2_core_reqbufs(struct vb2_queue *q
  96                  * are not in use and can be freed.
  97                  */
  98                 mutex_lock(&q->mmap_lock);
  99 -               if (q->memory == VB2_MEMORY_MMAP && __buffers_in_use(q)) {
 100 -                       mutex_unlock(&q->mmap_lock);
 101 -                       dprintk(1, "memory in use, cannot free\n");
 102 -                       return -EBUSY;
 103 -               }
 104 +               if (debug && q->memory == VB2_MEMORY_MMAP &&
 105 +                   __buffers_in_use(q))
 106 +                       dprintk(1, "memory in use, orphaning buffers\n");
 107
 108                 /*
 109                  * Call queue_cancel to clean up any buffers in the PREPARED or
 110 --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
 111 +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
 112 @@ -484,7 +484,7 @@ EXPORT_SYMBOL(vb2_querybuf);
 113
 114  static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
 115  {
 116 -       *caps = 0;
 117 +       *caps = V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
 118         if (q->io_modes & VB2_MMAP)
 119                 *caps |= V4L2_BUF_CAP_SUPPORTS_MMAP;
 120         if (q->io_modes & VB2_USERPTR)
 121 --- a/include/uapi/linux/videodev2.h
 122 +++ b/include/uapi/linux/videodev2.h
 123 @@ -881,6 +881,7 @@ struct v4l2_requestbuffers {
 124  #define V4L2_BUF_CAP_SUPPORTS_USERPTR  (1 << 1)
 125  #define V4L2_BUF_CAP_SUPPORTS_DMABUF   (1 << 2)
 126  #define V4L2_BUF_CAP_SUPPORTS_REQUESTS (1 << 3)
 127 +#define V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS (1 << 4)
 128
 129  /**
 130   * struct v4l2_plane - plane info for multi-planar buffers