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authorJohn Sheu <sheu@chromium.org>2018-11-15 10:57:16 -0500
committerMauro Carvalho Chehab <mchehab+samsung@kernel.org>2018-11-23 06:41:39 -0500
commitd644cca50f366cd109845ae92e37c09ed79adf81 (patch)
tree0e88bb38d94c1c1d1f5dcb76495b2dddf04e4161
parent949f29f6071416f847ed8d2b2ad3a5f702583468 (diff)
media: vb2: Allow reqbufs(0) with "in use" MMAP buffers
Videobuf2 presently does not allow VIDIOC_REQBUFS to destroy outstanding buffers if the queue is of type V4L2_MEMORY_MMAP, and if the buffers are considered "in use". This is different behavior than for other memory types and prevents us from deallocating buffers in following two cases: 1) There are outstanding mmap()ed views on the buffer. However even if we put the buffer in reqbufs(0), there will be remaining references, due to vma .open/close() adjusting vb2 buffer refcount appropriately. This means that the buffer will be in fact freed only when the last mmap()ed view is unmapped. 2) Buffer has been exported as a DMABUF. Refcount of the vb2 buffer is managed properly by VB2 DMABUF ops, i.e. incremented on DMABUF get and decremented on DMABUF release. This means that the buffer will be alive until all importers release it. Considering both cases above, there does not seem to be any need to prevent reqbufs(0) operation, because buffer lifetime is already properly managed by both mmap() and DMABUF code paths. Let's remove it and allow userspace freeing the queue (and potentially allocating a new one) even though old buffers might be still in processing. To let userspace know that the kernel now supports orphaning buffers that are still in use, add a new V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS to be set by reqbufs and create_bufs. [p.zabel@pengutronix.de: added V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS, updated documentation, and added back debug message] Signed-off-by: John Sheu <sheu@chromium.org> Reviewed-by: Pawel Osciak <posciak@chromium.org> Signed-off-by: Tomasz Figa <tfiga@chromium.org> Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de> Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> [hverkuil-cisco@xs4all.nl: added V4L2-BUF-CAP-SUPPORTS-ORPHANED-BUFS ref] Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
-rw-r--r--Documentation/media/uapi/v4l/vidioc-reqbufs.rst17
-rw-r--r--drivers/media/common/videobuf2/videobuf2-core.c8
-rw-r--r--drivers/media/common/videobuf2/videobuf2-v4l2.c2
-rw-r--r--include/uapi/linux/videodev2.h1
4 files changed, 19 insertions, 9 deletions
diff --git a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
index d4bbbb0c60e8..e62a15782790 100644
--- a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
+++ b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
@@ -59,9 +59,14 @@ When the I/O method is not supported the ioctl returns an ``EINVAL`` error
code.
Applications can call :ref:`VIDIOC_REQBUFS` again to change the number of
-buffers, however this cannot succeed when any buffers are still mapped.
-A ``count`` value of zero frees all buffers, after aborting or finishing
-any DMA in progress, an implicit
+buffers. Note that if any buffers are still mapped or exported via DMABUF,
+then :ref:`VIDIOC_REQBUFS` can only succeed if the
+``V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS`` capability is set. Otherwise
+:ref:`VIDIOC_REQBUFS` will return the ``EBUSY`` error code.
+If ``V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS`` is set, then these buffers are
+orphaned and will be freed when they are unmapped or when the exported DMABUF
+fds are closed. A ``count`` value of zero frees or orphans all buffers, after
+aborting or finishing any DMA in progress, an implicit
:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>`.
@@ -112,6 +117,7 @@ any DMA in progress, an implicit
.. _V4L2-BUF-CAP-SUPPORTS-USERPTR:
.. _V4L2-BUF-CAP-SUPPORTS-DMABUF:
.. _V4L2-BUF-CAP-SUPPORTS-REQUESTS:
+.. _V4L2-BUF-CAP-SUPPORTS-ORPHANED-BUFS:
.. cssclass:: longtable
@@ -132,6 +138,11 @@ any DMA in progress, an implicit
* - ``V4L2_BUF_CAP_SUPPORTS_REQUESTS``
- 0x00000008
- This buffer type supports :ref:`requests <media-request-api>`.
+ * - ``V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS``
+ - 0x00000010
+ - The kernel allows calling :ref:`VIDIOC_REQBUFS` while buffers are still
+ mapped or exported via DMABUF. These orphaned buffers will be freed
+ when they are unmapped or when the exported DMABUF fds are closed.
Return Value
============
diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index 03954c13024c..04d1250747cf 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -679,11 +679,9 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
* are not in use and can be freed.
*/
mutex_lock(&q->mmap_lock);
- if (q->memory == VB2_MEMORY_MMAP && __buffers_in_use(q)) {
- mutex_unlock(&q->mmap_lock);
- dprintk(1, "memory in use, cannot free\n");
- return -EBUSY;
- }
+ if (debug && q->memory == VB2_MEMORY_MMAP &&
+ __buffers_in_use(q))
+ dprintk(1, "memory in use, orphaning buffers\n");
/*
* Call queue_cancel to clean up any buffers in the
diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index a17033ab2c22..f02d452ceeb9 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -624,7 +624,7 @@ EXPORT_SYMBOL(vb2_querybuf);
static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
{
- *caps = 0;
+ *caps = V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
if (q->io_modes & VB2_MMAP)
*caps |= V4L2_BUF_CAP_SUPPORTS_MMAP;
if (q->io_modes & VB2_USERPTR)
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index c8e8ff810190..2a223835214c 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -879,6 +879,7 @@ struct v4l2_requestbuffers {
#define V4L2_BUF_CAP_SUPPORTS_USERPTR (1 << 1)
#define V4L2_BUF_CAP_SUPPORTS_DMABUF (1 << 2)
#define V4L2_BUF_CAP_SUPPORTS_REQUESTS (1 << 3)
+#define V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS (1 << 4)
/**
* struct v4l2_plane - plane info for multi-planar buffers