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131 lines
5.6 KiB
Diff
131 lines
5.6 KiB
Diff
From 16cf378051d7fff6772a7acaecbacddec7822330 Mon Sep 17 00:00:00 2001
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From: John Sheu <sheu@chromium.org>
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Date: Thu, 15 Nov 2018 10:57:16 -0500
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Subject: [PATCH] media: vb2: Allow reqbufs(0) with "in use" MMAP
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buffers
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Upstream commit d644cca50f366cd109845ae92e37c09ed79adf81
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Videobuf2 presently does not allow VIDIOC_REQBUFS to destroy outstanding
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buffers if the queue is of type V4L2_MEMORY_MMAP, and if the buffers are
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considered "in use". This is different behavior than for other memory
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types and prevents us from deallocating buffers in following two cases:
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1) There are outstanding mmap()ed views on the buffer. However even if
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we put the buffer in reqbufs(0), there will be remaining references,
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due to vma .open/close() adjusting vb2 buffer refcount appropriately.
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This means that the buffer will be in fact freed only when the last
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mmap()ed view is unmapped.
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2) Buffer has been exported as a DMABUF. Refcount of the vb2 buffer
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is managed properly by VB2 DMABUF ops, i.e. incremented on DMABUF
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get and decremented on DMABUF release. This means that the buffer
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will be alive until all importers release it.
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Considering both cases above, there does not seem to be any need to
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prevent reqbufs(0) operation, because buffer lifetime is already
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properly managed by both mmap() and DMABUF code paths. Let's remove it
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and allow userspace freeing the queue (and potentially allocating a new
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one) even though old buffers might be still in processing.
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To let userspace know that the kernel now supports orphaning buffers
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that are still in use, add a new V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS
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to be set by reqbufs and create_bufs.
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[p.zabel@pengutronix.de: added V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS,
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updated documentation, and added back debug message]
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Signed-off-by: John Sheu <sheu@chromium.org>
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Reviewed-by: Pawel Osciak <posciak@chromium.org>
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Signed-off-by: Tomasz Figa <tfiga@chromium.org>
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Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
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Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
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Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
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[hverkuil-cisco@xs4all.nl: added V4L2-BUF-CAP-SUPPORTS-ORPHANED-BUFS ref]
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Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
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---
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Documentation/media/uapi/v4l/vidioc-reqbufs.rst | 17 ++++++++++++++---
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drivers/media/common/videobuf2/videobuf2-core.c | 8 +++-----
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drivers/media/common/videobuf2/videobuf2-v4l2.c | 2 +-
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include/uapi/linux/videodev2.h | 1 +
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4 files changed, 19 insertions(+), 9 deletions(-)
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--- a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
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+++ b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
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@@ -59,9 +59,14 @@ When the I/O method is not supported the
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code.
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Applications can call :ref:`VIDIOC_REQBUFS` again to change the number of
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-buffers, however this cannot succeed when any buffers are still mapped.
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-A ``count`` value of zero frees all buffers, after aborting or finishing
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-any DMA in progress, an implicit
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+buffers. Note that if any buffers are still mapped or exported via DMABUF,
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+then :ref:`VIDIOC_REQBUFS` can only succeed if the
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+``V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS`` capability is set. Otherwise
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+:ref:`VIDIOC_REQBUFS` will return the ``EBUSY`` error code.
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+If ``V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS`` is set, then these buffers are
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+orphaned and will be freed when they are unmapped or when the exported DMABUF
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+fds are closed. A ``count`` value of zero frees or orphans all buffers, after
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+aborting or finishing any DMA in progress, an implicit
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:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>`.
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@@ -112,6 +117,7 @@ any DMA in progress, an implicit
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.. _V4L2-BUF-CAP-SUPPORTS-USERPTR:
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.. _V4L2-BUF-CAP-SUPPORTS-DMABUF:
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.. _V4L2-BUF-CAP-SUPPORTS-REQUESTS:
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+.. _V4L2-BUF-CAP-SUPPORTS-ORPHANED-BUFS:
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.. cssclass:: longtable
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@@ -132,6 +138,11 @@ any DMA in progress, an implicit
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* - ``V4L2_BUF_CAP_SUPPORTS_REQUESTS``
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- 0x00000008
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- This buffer type supports :ref:`requests <media-request-api>`.
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+ * - ``V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS``
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+ - 0x00000010
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+ - The kernel allows calling :ref:`VIDIOC_REQBUFS` while buffers are still
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+ mapped or exported via DMABUF. These orphaned buffers will be freed
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+ when they are unmapped or when the exported DMABUF fds are closed.
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Return Value
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============
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--- a/drivers/media/common/videobuf2/videobuf2-core.c
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+++ b/drivers/media/common/videobuf2/videobuf2-core.c
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@@ -684,11 +684,9 @@ int vb2_core_reqbufs(struct vb2_queue *q
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* are not in use and can be freed.
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*/
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mutex_lock(&q->mmap_lock);
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- if (q->memory == VB2_MEMORY_MMAP && __buffers_in_use(q)) {
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- mutex_unlock(&q->mmap_lock);
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- dprintk(1, "memory in use, cannot free\n");
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- return -EBUSY;
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- }
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+ if (debug && q->memory == VB2_MEMORY_MMAP &&
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+ __buffers_in_use(q))
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+ dprintk(1, "memory in use, orphaning buffers\n");
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/*
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* Call queue_cancel to clean up any buffers in the PREPARED or
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--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
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+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
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@@ -484,7 +484,7 @@ EXPORT_SYMBOL(vb2_querybuf);
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static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
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{
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- *caps = 0;
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+ *caps = V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
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if (q->io_modes & VB2_MMAP)
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*caps |= V4L2_BUF_CAP_SUPPORTS_MMAP;
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if (q->io_modes & VB2_USERPTR)
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--- a/include/uapi/linux/videodev2.h
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+++ b/include/uapi/linux/videodev2.h
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@@ -881,6 +881,7 @@ struct v4l2_requestbuffers {
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#define V4L2_BUF_CAP_SUPPORTS_USERPTR (1 << 1)
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#define V4L2_BUF_CAP_SUPPORTS_DMABUF (1 << 2)
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#define V4L2_BUF_CAP_SUPPORTS_REQUESTS (1 << 3)
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+#define V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS (1 << 4)
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/**
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* struct v4l2_plane - plane info for multi-planar buffers
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