[PATCHv3 00/11] Implement V4L2_BUF_FLAG_NO_CACHE_* flags

[PATCHv3 00/11] Implement V4L2_BUF_FLAG_NO_CACHE_* flags

[Sergey Senozhatsky]

Hello,

	V3 of the patchset, reshuffled and updated.

- Most notable changes:

a) Added a simple helper function vb2_queue_allows_cache_hints(),
   which return true if queue has ->allow_cache_hints and when
   ->memory is VB2_MEMORY_MMAP.
   That is - user space cache and memory consistency hints are now
   specifically for MMAP buffers and queues that support hints.

b) Set V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS capability bit only when queue
   has ->allow_cache_hints and ->io_modes has VB2_MMAP bit set

c) Clear "incompatible" request's flags when queue does not permit
   cache and memory consistency hints (IOW, when vb2_queue_allows_cache_hints()
   return false)


Minor changes:

- Squashed V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS and V4L2_FLAG_MEMORY_NON_CONSISTENT
  patches.

- Added more documentation and code comments.


Previous series:
v2 link: https://lore.kernel.org/lkml/20200204025641.218376-1-senozhatsky@chromium.org/
v1 link: https://lore.kernel.org/lkml/20191217032034.54897-1-senozhatsky@chromium.org/


Series Intro
========================================================================

        This is a reworked version of the vb2 cache hints
(V4L2_BUF_FLAG_NO_CACHE_INVALIDATE / V4L2_BUF_FLAG_NO_CACHE_CLEAN)
support patch series which previsouly was developed by Sakari and
Laurent [0].

The patch set attempts to preserve the existing behvaiour - cache
sync is performed in ->prepare() and ->finish() (unless the buffer
is DMA exported). User space can request “default behavior” override
with cache management hints, which are handled on a per-buffer basis
and should be supplied with v4l2_buffer ->flags during buffer
preparation. There are two possible hints:

- V4L2_BUF_FLAG_NO_CACHE_INVALIDATE
        No cache sync on ->finish()

- V4L2_BUF_FLAG_NO_CACHE_CLEAN
        No cache sync on ->prepare()

In order to keep things on the safe side, we also require driver
to explicitly state which of its queues (if any) support user space
cache management hints (such queues should have ->allow_cache_hints
bit set).

The patch set also (to some extent) simplifies allocators' ->prepare()
and ->finish() callbacks. Namely, we move cache management decision
making to the upper - core - layer. For example, if, previously, we
would have something like this

        vb2_buffer_done()
          vb2_dc_finish()
            if (buf->db_attach)
               return;

where each allocators' ->finish() callback would either bail
out (DMA exported buffer, for instance) or sync, now that "bail
out or sync" decision is made before we call into the allocator.

Along with cache management hints, user space is also able to
adjust queue's memory consistency attributes. Memory consistency
attribute (dma_attrs) is per-queue, yet it plays its role on the
allocator level, when we allocate buffers’ private memory (planes).
For the time being, only one consistency attribute is supported:
DMA_ATTR_NON_CONSISTENT.

[0] https://www.mail-archive.com/linux-media@vger.kernel.org/msg112459.html

Sergey Senozhatsky (11):
  videobuf2: add cache management members
  videobuf2: handle V4L2 buffer cache flags
  videobuf2: add V4L2_FLAG_MEMORY_NON_CONSISTENT flag
  videobuf2: add queue memory consistency parameter
  videobuf2: handle V4L2_FLAG_MEMORY_NON_CONSISTENT flag
  videobuf2: factor out planes prepare/finish functions
  videobuf2: do not sync caches when we are allowed not to
  videobuf2: check ->synced flag in prepare() and finish()
  videobuf2: add begin/end cpu_access callbacks to dma-contig
  videobuf2: add begin/end cpu_access callbacks to dma-sg
  videobuf2: don't test db_attach in dma-contig prepare and finish

 Documentation/media/uapi/v4l/buffer.rst       |  29 +++++
 .../media/uapi/v4l/vidioc-create-bufs.rst     |   8 +-
 .../media/uapi/v4l/vidioc-reqbufs.rst         |  22 +++-
 .../media/common/videobuf2/videobuf2-core.c   | 110 +++++++++++++-----
 .../common/videobuf2/videobuf2-dma-contig.c   |  39 ++++++-
 .../media/common/videobuf2/videobuf2-dma-sg.c |  36 ++++--
 .../media/common/videobuf2/videobuf2-v4l2.c   |  82 ++++++++++++-
 drivers/media/dvb-core/dvb_vb2.c              |   2 +-
 drivers/media/v4l2-core/v4l2-ioctl.c          |   5 +-
 include/media/videobuf2-core.h                |  28 ++++-
 include/uapi/linux/videodev2.h                |  11 +-
 11 files changed, 314 insertions(+), 58 deletions(-)

-- 
2.25.0.265.gbab2e86ba0-goog

[PATCHv3 01/11] videobuf2: add cache management members

[Sergey Senozhatsky]

Extend vb2_buffer and vb2_queue structs with cache management
members.

V4L2 UAPI already contains two buffer flags which user-space,
supposedly, can use to control buffer cache sync:

- V4L2_BUF_FLAG_NO_CACHE_INVALIDATE
- V4L2_BUF_FLAG_NO_CACHE_CLEAN

None of these, however, do anything at the moment. This patch
set is intended to change it.

Since user-space cache management hints are supposed to be
implemented on a per-buffer basis we need to extend vb2_buffer
struct with two new memebers ->need_cache_sync_on_prepare and
->need_cache_sync_on_finish, which will store corresponding
user-space hints.

In order to preserve the existing behaviour, user-space cache
managements flags will be handled only by those drivers that
permit user-space cache hints. That's the purpose of vb2_queue
->allow_cache_hints member. Driver must set ->allow_cache_hints
during queue initialisation to enable cache management hints
mechanism.

Only drivers that set ->allow_cache_hints during queue initialisation
will handle user-space cache management hints. Otherwise hints
will be ignored.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 include/media/videobuf2-core.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index a2b2208b02da..4a19170672ac 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -263,6 +263,10 @@ struct vb2_buffer {
 	 *			after the 'buf_finish' op is called.
 	 * copied_timestamp:	the timestamp of this capture buffer was copied
 	 *			from an output buffer.
+	 * need_cache_sync_on_prepare: when set buffer's ->prepare() function
+	 *			performs cache sync/invalidation.
+	 * need_cache_sync_on_finish: when set buffer's ->finish() function
+	 *			performs cache sync/invalidation.
 	 * queued_entry:	entry on the queued buffers list, which holds
 	 *			all buffers queued from userspace
 	 * done_entry:		entry on the list that stores all buffers ready
@@ -273,6 +277,8 @@ struct vb2_buffer {
 	unsigned int		synced:1;
 	unsigned int		prepared:1;
 	unsigned int		copied_timestamp:1;
+	unsigned int		need_cache_sync_on_prepare:1;
+	unsigned int		need_cache_sync_on_finish:1;
 
 	struct vb2_plane	planes[VB2_MAX_PLANES];
 	struct list_head	queued_entry;
@@ -491,6 +497,9 @@ struct vb2_buf_ops {
  * @uses_requests: requests are used for this queue. Set to 1 the first time
  *		a request is queued. Set to 0 when the queue is canceled.
  *		If this is 1, then you cannot queue buffers directly.
+ * @allow_cache_hints: when set user-space can pass cache management hints in
+ * 		order to skip cache flush/invalidation on ->prepare() or/and
+ * 		->finish().
  * @lock:	pointer to a mutex that protects the &struct vb2_queue. The
  *		driver can set this to a mutex to let the v4l2 core serialize
  *		the queuing ioctls. If the driver wants to handle locking
@@ -564,6 +573,7 @@ struct vb2_queue {
 	unsigned			requires_requests:1;
 	unsigned			uses_qbuf:1;
 	unsigned			uses_requests:1;
+	unsigned			allow_cache_hints:1;
 
 	struct mutex			*lock;
 	void				*owner;
-- 
2.25.0.265.gbab2e86ba0-goog

[PATCHv3 02/11] videobuf2: handle V4L2 buffer cache flags

[Sergey Senozhatsky]

Set video buffer cache management flags corresponding to V4L2 cache
flags.

Both ->prepare() and ->finish() cache management hints should be
passed during this stage (buffer preparation), because there is no
other way for user-space to skip ->finish() cache flush.

There are two possible alternative approaches:
- The first one is to move cache sync from ->finish() to dqbuf().
  But this breaks some drivers, that need to fix-up buffers before
  dequeueing them.

- The second one is to move ->finish() call from ->done() to dqbuf.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 .../media/common/videobuf2/videobuf2-v4l2.c   | 49 +++++++++++++++++++
 include/media/videobuf2-core.h                | 11 +++++
 2 files changed, 60 insertions(+)

diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index eb5d5db96552..2a604bd7793a 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -199,6 +199,15 @@ static int vb2_fill_vb2_v4l2_buffer(struct vb2_buffer *vb, struct v4l2_buffer *b
 	vbuf->request_fd = -1;
 	vbuf->is_held = false;
 
+	/*
+	 * Clear buffer cache flags if queue does not support user space hints.
+	 * That's to indicate to userspace that these flags won't work.
+	 */
+	if (!vb2_queue_allows_cache_hints(q)) {
+		b->flags &= ~V4L2_BUF_FLAG_NO_CACHE_INVALIDATE;
+		b->flags &= ~V4L2_BUF_FLAG_NO_CACHE_CLEAN;
+	}
+
 	if (V4L2_TYPE_IS_MULTIPLANAR(b->type)) {
 		switch (b->memory) {
 		case VB2_MEMORY_USERPTR:
@@ -337,6 +346,45 @@ static int vb2_fill_vb2_v4l2_buffer(struct vb2_buffer *vb, struct v4l2_buffer *b
 	return 0;
 }
 
+static void set_buffer_cache_hints(struct vb2_queue *q,
+				   struct vb2_buffer *vb,
+				   struct v4l2_buffer *b)
+{
+	/*
+	 * DMA exporter should take care of cache syncs, so we can avoid
+	 * explicit ->prepare()/->finish() syncs. For other ->memory types
+	 * we always need ->prepare() or/and ->finish() cache sync.
+	 */
+	if (q->memory == VB2_MEMORY_DMABUF) {
+		vb->need_cache_sync_on_finish = 0;
+		vb->need_cache_sync_on_prepare = 0;
+		return;
+	}
+
+	/*
+	 * Cache sync/invalidation flags are set by default in order to
+	 * preserve existing behaviour for old apps/drivers.
+	 */
+	vb->need_cache_sync_on_prepare = 1;
+	vb->need_cache_sync_on_finish = 1;
+
+	if (!vb2_queue_allows_cache_hints(q))
+		return;
+
+	/*
+	 * ->finish() cache sync can be avoided when queue direction is
+	 * TO_DEVICE.
+	 */
+	if (q->dma_dir == DMA_TO_DEVICE)
+		vb->need_cache_sync_on_finish = 0;
+
+	if (b->flags & V4L2_BUF_FLAG_NO_CACHE_INVALIDATE)
+		vb->need_cache_sync_on_finish = 0;
+
+	if (b->flags & V4L2_BUF_FLAG_NO_CACHE_CLEAN)
+		vb->need_cache_sync_on_prepare = 0;
+}
+
 static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct media_device *mdev,
 				    struct v4l2_buffer *b, bool is_prepare,
 				    struct media_request **p_req)
@@ -381,6 +429,7 @@ static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct media_device *md
 	}
 
 	if (!vb->prepared) {
+		set_buffer_cache_hints(q, vb, b);
 		/* Copy relevant information provided by the userspace */
 		memset(vbuf->planes, 0,
 		       sizeof(vbuf->planes[0]) * vb->num_planes);
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index 4a19170672ac..d307869bfb15 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -632,6 +632,17 @@ struct vb2_queue {
 #endif
 };
 
+/**
+ * vb2_queue_allows_cache_hints() - Return true if the queue allows cache
+ * and memory consistency hints.
+ *
+ * @q:		pointer to &struct vb2_queue with videobuf2 queue
+ */
+static inline bool vb2_queue_allows_cache_hints(struct vb2_queue *q)
+{
+	return (q->allow_cache_hints != 0) && (q->memory == VB2_MEMORY_MMAP);
+}
+
 /**
  * vb2_plane_vaddr() - Return a kernel virtual address of a given plane.
  * @vb:		pointer to &struct vb2_buffer to which the plane in
-- 
2.25.0.265.gbab2e86ba0-goog

[PATCHv3 03/11] videobuf2: add V4L2_FLAG_MEMORY_NON_CONSISTENT flag

[Sergey Senozhatsky]

By setting or clearing V4L2_FLAG_MEMORY_NON_CONSISTENT flag
user-space should be able to set or clear queue's NON_CONSISTENT
->dma_attrs. Queue's ->dma_attrs are passed to the underlying
allocator in __vb2_buf_mem_alloc(), so thus user-space is able
to request vb2 buffer's memory to be either consistent (coherent)
or non-consistent.

The patch set also adds a corresponding capability flag:
fill_buf_caps() reports V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS when
queue supports user-space cache management hints.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 Documentation/media/uapi/v4l/buffer.rst       | 29 +++++++++++++++++++
 .../media/uapi/v4l/vidioc-reqbufs.rst         |  7 +++++
 .../media/common/videobuf2/videobuf2-v4l2.c   |  2 ++
 include/uapi/linux/videodev2.h                |  3 ++
 4 files changed, 41 insertions(+)

diff --git a/Documentation/media/uapi/v4l/buffer.rst b/Documentation/media/uapi/v4l/buffer.rst
index 3112300c2fa0..6b629ac59bf2 100644
--- a/Documentation/media/uapi/v4l/buffer.rst
+++ b/Documentation/media/uapi/v4l/buffer.rst
@@ -681,6 +681,35 @@ Buffer Flags
 
     \normalsize
 
+.. _memory-flags:
+
+Memory Consistency Flags
+========================
+
+.. tabularcolumns:: |p{7.0cm}|p{2.2cm}|p{8.3cm}|
+
+.. cssclass:: longtable
+
+.. flat-table::
+    :header-rows:  0
+    :stub-columns: 0
+    :widths:       3 1 4
+
+    * .. _`V4L2_FLAG_MEMORY_NON_CONSISTENT`:
+
+      - ``V4L2_FLAG_MEMORY_NON_CONSISTENT``
+      - 0x00000001
+      - vb2 buffer is allocated either in consistent (it will be automatically
+	coherent between CPU and bus) or non-consistent memory. The latter
+	can provide performance gains, for instance CPU cache sync/flush
+	operations can be avoided if the buffer is accessed by the corresponding
+	device only and CPU does not read/write to/from that buffer. However,
+	this requires extra care from the driver -- it must guarantee memory
+	consistency by issuing cache flush/sync when consistency is needed.
+	If this flag is set V4L2 will attempt to allocate vb2 buffer in
+	non-consistent memory. The flag takes effect only if the buffer is
+	used for :ref:`memory mapping <mmap>` I/O and the queue reports
+	:ref:`V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS` capability.
 
 .. c:type:: v4l2_memory
 
diff --git a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
index d0c643db477a..917df6fb6486 100644
--- a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
+++ b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
@@ -156,6 +156,13 @@ aborting or finishing any DMA in progress, an implicit
       - Only valid for stateless decoders. If set, then userspace can set the
         ``V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF`` flag to hold off on returning the
 	capture buffer until the OUTPUT timestamp changes.
+    * - ``V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS``
+      - 0x00000040
+      - Set when the queue/buffer support memory consistency and cache
+        management hints. See :ref:`V4L2_FLAG_MEMORY_NON_CONSISTENT`,
+        :ref:`V4L2_BUF_FLAG_NO_CACHE_INVALIDATE` and
+        :ref:`V4L2_BUF_FLAG_NO_CACHE_CLEAN`.
+
 
 Return Value
 ============
diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index 2a604bd7793a..f91cba37e223 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -711,6 +711,8 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
 		*caps |= V4L2_BUF_CAP_SUPPORTS_DMABUF;
 	if (q->subsystem_flags & VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF)
 		*caps |= V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF;
+	if ((q->allow_cache_hints != 0) && (q->io_modes & VB2_MMAP))
+		*caps |= V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS;
 #ifdef CONFIG_MEDIA_CONTROLLER_REQUEST_API
 	if (q->supports_requests)
 		*caps |= V4L2_BUF_CAP_SUPPORTS_REQUESTS;
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index 5f9357dcb060..e92c29864730 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -189,6 +189,8 @@ enum v4l2_memory {
 	V4L2_MEMORY_DMABUF           = 4,
 };
 
+#define V4L2_FLAG_MEMORY_NON_CONSISTENT		(1 << 0)
+
 /* see also http://vektor.theorem.ca/graphics/ycbcr/ */
 enum v4l2_colorspace {
 	/*
@@ -946,6 +948,7 @@ struct v4l2_requestbuffers {
 #define V4L2_BUF_CAP_SUPPORTS_REQUESTS			(1 << 3)
 #define V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS		(1 << 4)
 #define V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF	(1 << 5)
+#define V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS		(1 << 6)
 
 /**
  * struct v4l2_plane - plane info for multi-planar buffers
-- 
2.25.0.265.gbab2e86ba0-goog

[PATCHv3 04/11] videobuf2: add queue memory consistency parameter

[Sergey Senozhatsky]

Preparations for future V4L2_FLAG_MEMORY_NON_CONSISTENT support.

Extend vb2_core_reqbufs() with queue memory consistency flag
that is applied to the newly allocated buffers.

An attempt to allocate a buffer with consistency requirements
which don't match queue's consistency model will fail.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 .../media/common/videobuf2/videobuf2-core.c   | 47 +++++++++++++++----
 .../media/common/videobuf2/videobuf2-v4l2.c   |  6 +--
 drivers/media/dvb-core/dvb_vb2.c              |  2 +-
 include/media/videobuf2-core.h                |  7 ++-
 4 files changed, 47 insertions(+), 15 deletions(-)

diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index 4489744fbbd9..3ca0545db7ee 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -664,8 +664,19 @@ int vb2_verify_memory_type(struct vb2_queue *q,
 }
 EXPORT_SYMBOL(vb2_verify_memory_type);
 
+static void set_queue_consistency(struct vb2_queue *q, bool consistent_mem)
+{
+	if (!vb2_queue_allows_cache_hints(q))
+		return;
+
+	if (consistent_mem)
+		q->dma_attrs &= ~DMA_ATTR_NON_CONSISTENT;
+	else
+		q->dma_attrs |= DMA_ATTR_NON_CONSISTENT;
+}
+
 int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
-		unsigned int *count)
+		bool consistent_mem, unsigned int *count)
 {
 	unsigned int num_buffers, allocated_buffers, num_planes = 0;
 	unsigned plane_sizes[VB2_MAX_PLANES] = { };
@@ -720,6 +731,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
 	num_buffers = min_t(unsigned int, num_buffers, VB2_MAX_FRAME);
 	memset(q->alloc_devs, 0, sizeof(q->alloc_devs));
 	q->memory = memory;
+	set_queue_consistency(q, consistent_mem);
 
 	/*
 	 * Ask the driver how many buffers and planes per buffer it requires.
@@ -803,9 +815,21 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
 }
 EXPORT_SYMBOL_GPL(vb2_core_reqbufs);
 
+static bool verify_consistency_attr(struct vb2_queue *q, bool consistent_mem)
+{
+	bool queue_attr = q->dma_attrs & DMA_ATTR_NON_CONSISTENT;
+
+	if (consistent_mem != queue_attr) {
+		dprintk(1, "memory consistency model mismatch\n");
+		return false;
+	}
+	return true;
+}
+
 int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
-		unsigned int *count, unsigned requested_planes,
-		const unsigned requested_sizes[])
+			 bool consistent_mem, unsigned int *count,
+			 unsigned requested_planes,
+			 const unsigned requested_sizes[])
 {
 	unsigned int num_planes = 0, num_buffers, allocated_buffers;
 	unsigned plane_sizes[VB2_MAX_PLANES] = { };
@@ -823,10 +847,15 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
 		}
 		memset(q->alloc_devs, 0, sizeof(q->alloc_devs));
 		q->memory = memory;
+		set_queue_consistency(q, consistent_mem);
 		q->waiting_for_buffers = !q->is_output;
-	} else if (q->memory != memory) {
-		dprintk(1, "memory model mismatch\n");
-		return -EINVAL;
+	} else {
+		if (q->memory != memory) {
+			dprintk(1, "memory model mismatch\n");
+			return -EINVAL;
+		}
+		if (!verify_consistency_attr(q, consistent_mem))
+			return -EINVAL;
 	}
 
 	num_buffers = min(*count, VB2_MAX_FRAME - q->num_buffers);
@@ -2498,7 +2527,7 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
 	fileio->memory = VB2_MEMORY_MMAP;
 	fileio->type = q->type;
 	q->fileio = fileio;
-	ret = vb2_core_reqbufs(q, fileio->memory, &fileio->count);
+	ret = vb2_core_reqbufs(q, fileio->memory, true, &fileio->count);
 	if (ret)
 		goto err_kfree;
 
@@ -2555,7 +2584,7 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
 
 err_reqbufs:
 	fileio->count = 0;
-	vb2_core_reqbufs(q, fileio->memory, &fileio->count);
+	vb2_core_reqbufs(q, fileio->memory, true, &fileio->count);
 
 err_kfree:
 	q->fileio = NULL;
@@ -2575,7 +2604,7 @@ static int __vb2_cleanup_fileio(struct vb2_queue *q)
 		vb2_core_streamoff(q, q->type);
 		q->fileio = NULL;
 		fileio->count = 0;
-		vb2_core_reqbufs(q, fileio->memory, &fileio->count);
+		vb2_core_reqbufs(q, fileio->memory, true, &fileio->count);
 		kfree(fileio);
 		dprintk(3, "file io emulator closed\n");
 	}
diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index f91cba37e223..cc31629c06dc 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -724,7 +724,7 @@ int vb2_reqbufs(struct vb2_queue *q, struct v4l2_requestbuffers *req)
 	int ret = vb2_verify_memory_type(q, req->memory, req->type);
 
 	fill_buf_caps(q, &req->capabilities);
-	return ret ? ret : vb2_core_reqbufs(q, req->memory, &req->count);
+	return ret ? ret : vb2_core_reqbufs(q, req->memory, true, &req->count);
 }
 EXPORT_SYMBOL_GPL(vb2_reqbufs);
 
@@ -798,7 +798,7 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
 	for (i = 0; i < requested_planes; i++)
 		if (requested_sizes[i] == 0)
 			return -EINVAL;
-	return ret ? ret : vb2_core_create_bufs(q, create->memory,
+	return ret ? ret : vb2_core_create_bufs(q, create->memory, true,
 		&create->count, requested_planes, requested_sizes);
 }
 EXPORT_SYMBOL_GPL(vb2_create_bufs);
@@ -974,7 +974,7 @@ int vb2_ioctl_reqbufs(struct file *file, void *priv,
 		return res;
 	if (vb2_queue_is_busy(vdev, file))
 		return -EBUSY;
-	res = vb2_core_reqbufs(vdev->queue, p->memory, &p->count);
+	res = vb2_core_reqbufs(vdev->queue, p->memory, true, &p->count);
 	/* If count == 0, then the owner has released all buffers and he
 	   is no longer owner of the queue. Otherwise we have a new owner. */
 	if (res == 0)
diff --git a/drivers/media/dvb-core/dvb_vb2.c b/drivers/media/dvb-core/dvb_vb2.c
index 6974f1731529..e60063652164 100644
--- a/drivers/media/dvb-core/dvb_vb2.c
+++ b/drivers/media/dvb-core/dvb_vb2.c
@@ -342,7 +342,7 @@ int dvb_vb2_reqbufs(struct dvb_vb2_ctx *ctx, struct dmx_requestbuffers *req)
 
 	ctx->buf_siz = req->size;
 	ctx->buf_cnt = req->count;
-	ret = vb2_core_reqbufs(&ctx->vb_q, VB2_MEMORY_MMAP, &req->count);
+	ret = vb2_core_reqbufs(&ctx->vb_q, VB2_MEMORY_MMAP, true, &req->count);
 	if (ret) {
 		ctx->state = DVB_VB2_STATE_NONE;
 		dprintk(1, "[%s] count=%d size=%d errno=%d\n", ctx->name,
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index d307869bfb15..d7fbf2ae9979 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -737,6 +737,7 @@ void vb2_core_querybuf(struct vb2_queue *q, unsigned int index, void *pb);
  * vb2_core_reqbufs() - Initiate streaming.
  * @q:		pointer to &struct vb2_queue with videobuf2 queue.
  * @memory:	memory type, as defined by &enum vb2_memory.
+ * @consistent_mem:	memory consistency model.
  * @count:	requested buffer count.
  *
  * Videobuf2 core helper to implement VIDIOC_REQBUF() operation. It is called
@@ -761,12 +762,13 @@ void vb2_core_querybuf(struct vb2_queue *q, unsigned int index, void *pb);
  * Return: returns zero on success; an error code otherwise.
  */
 int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
-		unsigned int *count);
+		bool consistent_mem, unsigned int *count);
 
 /**
  * vb2_core_create_bufs() - Allocate buffers and any required auxiliary structs
  * @q: pointer to &struct vb2_queue with videobuf2 queue.
  * @memory: memory type, as defined by &enum vb2_memory.
+ * @consistent_mem: memory consistency model.
  * @count: requested buffer count.
  * @requested_planes: number of planes requested.
  * @requested_sizes: array with the size of the planes.
@@ -784,7 +786,8 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
  * Return: returns zero on success; an error code otherwise.
  */
 int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
-			 unsigned int *count, unsigned int requested_planes,
+			 bool consistent_mem, unsigned int *count,
+			 unsigned int requested_planes,
 			 const unsigned int requested_sizes[]);
 
 /**
-- 
2.25.0.265.gbab2e86ba0-goog

[PATCHv3 05/11] videobuf2: handle V4L2_FLAG_MEMORY_NON_CONSISTENT flag

[Sergey Senozhatsky]

This patch lets user-space to request a non-consistent memory
allocation during CREATE_BUFS and REQBUFS ioctl calls.

= CREATE_BUFS

  struct v4l2_create_buffers has seven 4-byte reserved areas,
  so reserved[0] is renamed to ->flags. The struct, thus, now
  has six reserved 4-byte regions.

= REQBUFS

 We use one bit of a ->reserved[1] member of struct v4l2_requestbuffers,
 which is now renamed to ->flags. Unlike v4l2_create_buffers, struct
 v4l2_requestbuffers does not have enough reserved room. Therefore for
 backward compatibility  ->reserved and ->flags were put into anonymous
 union.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 .../media/uapi/v4l/vidioc-create-bufs.rst     |  8 ++++-
 .../media/uapi/v4l/vidioc-reqbufs.rst         | 15 +++++++--
 .../media/common/videobuf2/videobuf2-v4l2.c   | 31 +++++++++++++++++--
 drivers/media/v4l2-core/v4l2-ioctl.c          |  5 +--
 include/uapi/linux/videodev2.h                |  8 +++--
 5 files changed, 54 insertions(+), 13 deletions(-)

diff --git a/Documentation/media/uapi/v4l/vidioc-create-bufs.rst b/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
index bd08e4f77ae4..6a8a4d5de2f1 100644
--- a/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
+++ b/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
@@ -121,7 +121,13 @@ than the number requested.
 	other changes, then set ``count`` to 0, ``memory`` to
 	``V4L2_MEMORY_MMAP`` and ``format.type`` to the buffer type.
     * - __u32
-      - ``reserved``\ [7]
+      - ``flags``
+      - Specifies additional buffer management attributes.
+	See :ref:`memory-flags`. Old drivers and applications must set it to
+	zero.
+
+    * - __u32
+      - ``reserved``\ [6]
       - A place holder for future extensions. Drivers and applications
 	must set the array to zero.
 
diff --git a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
index 917df6fb6486..e52cc4401fba 100644
--- a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
+++ b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
@@ -112,10 +112,19 @@ aborting or finishing any DMA in progress, an implicit
 	``V4L2_MEMORY_MMAP`` and ``type`` set to the buffer type. This will
 	free any previously allocated buffers, so this is typically something
 	that will be done at the start of the application.
-    * - __u32
+    * - union
+      - (anonymous)
+    * -
+      - __u32
+      - ``flags``\ [1]
+      - Specifies additional buffer management attributes.
+	See :ref:`memory-flags`. Old drivers and applications must set it to
+	zero.
+
+    * -
+      - __u32
       - ``reserved``\ [1]
-      - A place holder for future extensions. Drivers and applications
-	must set the array to zero.
+      - Kept for backwards compatibility. Use ``flags`` instead.
 
 .. tabularcolumns:: |p{6.1cm}|p{2.2cm}|p{8.7cm}|
 
diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index cc31629c06dc..4954c9fc678d 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -722,9 +722,18 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
 int vb2_reqbufs(struct vb2_queue *q, struct v4l2_requestbuffers *req)
 {
 	int ret = vb2_verify_memory_type(q, req->memory, req->type);
+	bool consistent = true;
+
+	if (!vb2_queue_allows_cache_hints(q))
+		req->flags &= ~V4L2_FLAG_MEMORY_NON_CONSISTENT;
+
+	if (req->flags & V4L2_FLAG_MEMORY_NON_CONSISTENT)
+		consistent = false;
 
 	fill_buf_caps(q, &req->capabilities);
-	return ret ? ret : vb2_core_reqbufs(q, req->memory, true, &req->count);
+	if (ret)
+		return ret;
+	return vb2_core_reqbufs(q, req->memory, consistent, &req->count);
 }
 EXPORT_SYMBOL_GPL(vb2_reqbufs);
 
@@ -753,6 +762,7 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
 	unsigned requested_sizes[VIDEO_MAX_PLANES];
 	struct v4l2_format *f = &create->format;
 	int ret = vb2_verify_memory_type(q, create->memory, f->type);
+	bool consistent = true;
 	unsigned i;
 
 	fill_buf_caps(q, &create->capabilities);
@@ -798,7 +808,14 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
 	for (i = 0; i < requested_planes; i++)
 		if (requested_sizes[i] == 0)
 			return -EINVAL;
-	return ret ? ret : vb2_core_create_bufs(q, create->memory, true,
+
+	if (!vb2_queue_allows_cache_hints(q))
+		create->flags &= ~V4L2_FLAG_MEMORY_NON_CONSISTENT;
+
+	if (create->flags & V4L2_FLAG_MEMORY_NON_CONSISTENT)
+		consistent = false;
+
+	return ret ? ret : vb2_core_create_bufs(q, create->memory, consistent,
 		&create->count, requested_planes, requested_sizes);
 }
 EXPORT_SYMBOL_GPL(vb2_create_bufs);
@@ -968,13 +985,21 @@ int vb2_ioctl_reqbufs(struct file *file, void *priv,
 {
 	struct video_device *vdev = video_devdata(file);
 	int res = vb2_verify_memory_type(vdev->queue, p->memory, p->type);
+	bool consistent = true;
 
 	fill_buf_caps(vdev->queue, &p->capabilities);
 	if (res)
 		return res;
 	if (vb2_queue_is_busy(vdev, file))
 		return -EBUSY;
-	res = vb2_core_reqbufs(vdev->queue, p->memory, true, &p->count);
+
+	if (!vb2_queue_allows_cache_hints(vdev->queue))
+		p->flags &= ~V4L2_FLAG_MEMORY_NON_CONSISTENT;
+
+	if (p->flags & V4L2_FLAG_MEMORY_NON_CONSISTENT)
+		consistent = false;
+
+	res = vb2_core_reqbufs(vdev->queue, p->memory, consistent, &p->count);
 	/* If count == 0, then the owner has released all buffers and he
 	   is no longer owner of the queue. Otherwise we have a new owner. */
 	if (res == 0)
diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
index fbcc7a20eedf..53b87bfd50d7 100644
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -1973,9 +1973,6 @@ static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,
 
 	if (ret)
 		return ret;
-
-	CLEAR_AFTER_FIELD(p, capabilities);
-
 	return ops->vidioc_reqbufs(file, fh, p);
 }
 
@@ -2015,7 +2012,7 @@ static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
 	if (ret)
 		return ret;
 
-	CLEAR_AFTER_FIELD(create, capabilities);
+	CLEAR_AFTER_FIELD(create, flags);
 
 	v4l_sanitize_format(&create->format);
 
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index e92c29864730..12b1bd220347 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -938,7 +938,10 @@ struct v4l2_requestbuffers {
 	__u32			type;		/* enum v4l2_buf_type */
 	__u32			memory;		/* enum v4l2_memory */
 	__u32			capabilities;
-	__u32			reserved[1];
+	union {
+		__u32		flags;
+		__u32		reserved[1];
+	};
 };
 
 /* capabilities for struct v4l2_requestbuffers and v4l2_create_buffers */
@@ -2446,7 +2449,8 @@ struct v4l2_create_buffers {
 	__u32			memory;
 	struct v4l2_format	format;
 	__u32			capabilities;
-	__u32			reserved[7];
+	__u32			flags;
+	__u32			reserved[6];
 };
 
 /*
-- 
2.25.0.265.gbab2e86ba0-goog

[PATCHv3 06/11] videobuf2: factor out planes prepare/finish functions

[Sergey Senozhatsky]

Factor out the code, no functional changes.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 .../media/common/videobuf2/videobuf2-core.c   | 52 +++++++++++--------
 1 file changed, 31 insertions(+), 21 deletions(-)

diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index 3ca0545db7ee..c2a1eadb26cf 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -296,6 +296,32 @@ static void __vb2_buf_dmabuf_put(struct vb2_buffer *vb)
 		__vb2_plane_dmabuf_put(vb, &vb->planes[plane]);
 }
 
+/*
+ * __vb2_buf_mem_prepare() - call ->prepare() on buffer's private memory
+ * to sync caches
+ */
+static void __vb2_buf_mem_prepare(struct vb2_buffer *vb)
+{
+	unsigned int plane;
+
+	for (plane = 0; plane < vb->num_planes; ++plane)
+		call_void_memop(vb, prepare, vb->planes[plane].mem_priv);
+	vb->synced = 1;
+}
+
+/*
+ * __vb2_buf_mem_finish() - call ->finish on buffer's private memory
+ * to sync caches
+ */
+static void __vb2_buf_mem_finish(struct vb2_buffer *vb)
+{
+	unsigned int plane;
+
+	for (plane = 0; plane < vb->num_planes; ++plane)
+		call_void_memop(vb, finish, vb->planes[plane].mem_priv);
+	vb->synced = 0;
+}
+
 /*
  * __setup_offsets() - setup unique offsets ("cookies") for every plane in
  * the buffer.
@@ -951,7 +977,6 @@ void vb2_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state state)
 {
 	struct vb2_queue *q = vb->vb2_queue;
 	unsigned long flags;
-	unsigned int plane;
 
 	if (WARN_ON(vb->state != VB2_BUF_STATE_ACTIVE))
 		return;
@@ -971,12 +996,8 @@ void vb2_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state state)
 	dprintk(4, "done processing on buffer %d, state: %d\n",
 			vb->index, state);
 
-	if (state != VB2_BUF_STATE_QUEUED) {
-		/* sync buffers */
-		for (plane = 0; plane < vb->num_planes; ++plane)
-			call_void_memop(vb, finish, vb->planes[plane].mem_priv);
-		vb->synced = 0;
-	}
+	if (state != VB2_BUF_STATE_QUEUED)
+		__vb2_buf_mem_finish(vb);
 
 	spin_lock_irqsave(&q->done_lock, flags);
 	if (state == VB2_BUF_STATE_QUEUED) {
@@ -1301,7 +1322,6 @@ static int __buf_prepare(struct vb2_buffer *vb)
 {
 	struct vb2_queue *q = vb->vb2_queue;
 	enum vb2_buffer_state orig_state = vb->state;
-	unsigned int plane;
 	int ret;
 
 	if (q->error) {
@@ -1345,11 +1365,7 @@ static int __buf_prepare(struct vb2_buffer *vb)
 		return ret;
 	}
 
-	/* sync buffers */
-	for (plane = 0; plane < vb->num_planes; ++plane)
-		call_void_memop(vb, prepare, vb->planes[plane].mem_priv);
-
-	vb->synced = 1;
+	__vb2_buf_mem_prepare(vb);
 	vb->prepared = 1;
 	vb->state = orig_state;
 
@@ -1969,14 +1985,8 @@ static void __vb2_queue_cancel(struct vb2_queue *q)
 				call_void_vb_qop(vb, buf_request_complete, vb);
 		}
 
-		if (vb->synced) {
-			unsigned int plane;
-
-			for (plane = 0; plane < vb->num_planes; ++plane)
-				call_void_memop(vb, finish,
-						vb->planes[plane].mem_priv);
-			vb->synced = 0;
-		}
+		if (vb->synced)
+			__vb2_buf_mem_finish(vb);
 
 		if (vb->prepared) {
 			call_void_vb_qop(vb, buf_finish, vb);
-- 
2.25.0.265.gbab2e86ba0-goog

[PATCHv3 07/11] videobuf2: do not sync caches when we are allowed not to

[Sergey Senozhatsky]

Skip ->prepare() or/and ->finish() cache synchronisation if
user-space requested us to do so (or when queue dma direction
permits us to skip cache syncs).

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 drivers/media/common/videobuf2/videobuf2-core.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index c2a1eadb26cf..988e8796de4f 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -304,8 +304,11 @@ static void __vb2_buf_mem_prepare(struct vb2_buffer *vb)
 {
 	unsigned int plane;
 
-	for (plane = 0; plane < vb->num_planes; ++plane)
-		call_void_memop(vb, prepare, vb->planes[plane].mem_priv);
+	if (vb->need_cache_sync_on_prepare) {
+		for (plane = 0; plane < vb->num_planes; ++plane)
+			call_void_memop(vb, prepare,
+					vb->planes[plane].mem_priv);
+	}
 	vb->synced = 1;
 }
 
@@ -317,8 +320,11 @@ static void __vb2_buf_mem_finish(struct vb2_buffer *vb)
 {
 	unsigned int plane;
 
-	for (plane = 0; plane < vb->num_planes; ++plane)
-		call_void_memop(vb, finish, vb->planes[plane].mem_priv);
+	if (vb->need_cache_sync_on_finish) {
+		for (plane = 0; plane < vb->num_planes; ++plane)
+			call_void_memop(vb, finish,
+					vb->planes[plane].mem_priv);
+	}
 	vb->synced = 0;
 }
 
-- 
2.25.0.265.gbab2e86ba0-goog

[PATCHv3 08/11] videobuf2: check ->synced flag in prepare() and finish()

[Sergey Senozhatsky]

This simplifies the code a tiny bit and let's us to avoid
unneeded ->prepare()/->finish() calls.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 drivers/media/common/videobuf2/videobuf2-core.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index 988e8796de4f..7f637e3a50ab 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -304,6 +304,9 @@ static void __vb2_buf_mem_prepare(struct vb2_buffer *vb)
 {
 	unsigned int plane;
 
+	if (vb->synced)
+		return;
+
 	if (vb->need_cache_sync_on_prepare) {
 		for (plane = 0; plane < vb->num_planes; ++plane)
 			call_void_memop(vb, prepare,
@@ -320,6 +323,9 @@ static void __vb2_buf_mem_finish(struct vb2_buffer *vb)
 {
 	unsigned int plane;
 
+	if (!vb->synced)
+		return;
+
 	if (vb->need_cache_sync_on_finish) {
 		for (plane = 0; plane < vb->num_planes; ++plane)
 			call_void_memop(vb, finish,
@@ -1991,8 +1997,7 @@ static void __vb2_queue_cancel(struct vb2_queue *q)
 				call_void_vb_qop(vb, buf_request_complete, vb);
 		}
 
-		if (vb->synced)
-			__vb2_buf_mem_finish(vb);
+		__vb2_buf_mem_finish(vb);
 
 		if (vb->prepared) {
 			call_void_vb_qop(vb, buf_finish, vb);
-- 
2.25.0.265.gbab2e86ba0-goog

[PATCHv3 09/11] videobuf2: add begin/end cpu_access callbacks to dma-contig

[Sergey Senozhatsky]

Provide begin_cpu_access() and end_cpu_access() callbacks for
cache synchronisation on exported buffers.

The patch also adds a new helper function - vb2_dc_buffer_consistent(),
which returns true is if the buffer is consistent (DMA_ATTR_NON_CONSISTENT
bit cleared), so then we don't need to sync anything.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 .../common/videobuf2/videobuf2-dma-contig.c   | 33 +++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
index d0c9dffe49e5..a387260fb321 100644
--- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c
+++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
@@ -42,6 +42,11 @@ struct vb2_dc_buf {
 	struct dma_buf_attachment	*db_attach;
 };
 
+static inline bool vb2_dc_buffer_consistent(unsigned long attr)
+{
+	return !(attr & DMA_ATTR_NON_CONSISTENT);
+}
+
 /*********************************************/
 /*        scatterlist table functions        */
 /*********************************************/
@@ -335,6 +340,32 @@ static void vb2_dc_dmabuf_ops_release(struct dma_buf *dbuf)
 	vb2_dc_put(dbuf->priv);
 }
 
+static int vb2_dc_dmabuf_ops_begin_cpu_access(struct dma_buf *dbuf,
+					      enum dma_data_direction direction)
+{
+	struct vb2_dc_buf *buf = dbuf->priv;
+	struct sg_table *sgt = buf->dma_sgt;
+
+	if (vb2_dc_buffer_consistent(buf->attrs))
+		return 0;
+
+	dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
+	return 0;
+}
+
+static int vb2_dc_dmabuf_ops_end_cpu_access(struct dma_buf *dbuf,
+					    enum dma_data_direction direction)
+{
+	struct vb2_dc_buf *buf = dbuf->priv;
+	struct sg_table *sgt = buf->dma_sgt;
+
+	if (vb2_dc_buffer_consistent(buf->attrs))
+		return 0;
+
+	dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
+	return 0;
+}
+
 static void *vb2_dc_dmabuf_ops_vmap(struct dma_buf *dbuf)
 {
 	struct vb2_dc_buf *buf = dbuf->priv;
@@ -353,6 +384,8 @@ static const struct dma_buf_ops vb2_dc_dmabuf_ops = {
 	.detach = vb2_dc_dmabuf_ops_detach,
 	.map_dma_buf = vb2_dc_dmabuf_ops_map,
 	.unmap_dma_buf = vb2_dc_dmabuf_ops_unmap,
+	.begin_cpu_access = vb2_dc_dmabuf_ops_begin_cpu_access,
+	.end_cpu_access = vb2_dc_dmabuf_ops_end_cpu_access,
 	.vmap = vb2_dc_dmabuf_ops_vmap,
 	.mmap = vb2_dc_dmabuf_ops_mmap,
 	.release = vb2_dc_dmabuf_ops_release,
-- 
2.25.0.265.gbab2e86ba0-goog

[PATCHv3 10/11] videobuf2: add begin/end cpu_access callbacks to dma-sg

[Sergey Senozhatsky]

Provide begin_cpu_access() and end_cpu_access() dma_buf_ops
callbacks for cache synchronisation on exported buffers.

V4L2_FLAG_MEMORY_NON_CONSISTENT has no effect on dma-sg buffers.
dma-sg allocates memory using the page allocator directly, so
there is no memory consistency guarantee.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 .../media/common/videobuf2/videobuf2-dma-sg.c | 28 +++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/drivers/media/common/videobuf2/videobuf2-dma-sg.c b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
index 6db60e9d5183..ddc67c9aaedb 100644
--- a/drivers/media/common/videobuf2/videobuf2-dma-sg.c
+++ b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
@@ -120,6 +120,12 @@ static void *vb2_dma_sg_alloc(struct device *dev, unsigned long dma_attrs,
 	buf->num_pages = size >> PAGE_SHIFT;
 	buf->dma_sgt = &buf->sg_table;
 
+	/*
+	 * NOTE: dma-sg allocates memory using the page allocator directly, so
+	 * there is no memory consistency guarantee, hence dma-sg ignores DMA
+	 * attributes passed from the upper layer. That means that
+	 * V4L2_FLAG_MEMORY_NON_CONSISTENT has no effect on dma-sg buffers.
+	 */
 	buf->pages = kvmalloc_array(buf->num_pages, sizeof(struct page *),
 				    GFP_KERNEL | __GFP_ZERO);
 	if (!buf->pages)
@@ -470,6 +476,26 @@ static void vb2_dma_sg_dmabuf_ops_release(struct dma_buf *dbuf)
 	vb2_dma_sg_put(dbuf->priv);
 }
 
+static int vb2_dma_sg_dmabuf_ops_begin_cpu_access(struct dma_buf *dbuf,
+					enum dma_data_direction direction)
+{
+	struct vb2_dma_sg_buf *buf = dbuf->priv;
+	struct sg_table *sgt = buf->dma_sgt;
+
+	dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
+	return 0;
+}
+
+static int vb2_dma_sg_dmabuf_ops_end_cpu_access(struct dma_buf *dbuf,
+					enum dma_data_direction direction)
+{
+	struct vb2_dma_sg_buf *buf = dbuf->priv;
+	struct sg_table *sgt = buf->dma_sgt;
+
+	dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
+	return 0;
+}
+
 static void *vb2_dma_sg_dmabuf_ops_vmap(struct dma_buf *dbuf)
 {
 	struct vb2_dma_sg_buf *buf = dbuf->priv;
@@ -488,6 +514,8 @@ static const struct dma_buf_ops vb2_dma_sg_dmabuf_ops = {
 	.detach = vb2_dma_sg_dmabuf_ops_detach,
 	.map_dma_buf = vb2_dma_sg_dmabuf_ops_map,
 	.unmap_dma_buf = vb2_dma_sg_dmabuf_ops_unmap,
+	.begin_cpu_access = vb2_dma_sg_dmabuf_ops_begin_cpu_access,
+	.end_cpu_access = vb2_dma_sg_dmabuf_ops_end_cpu_access,
 	.vmap = vb2_dma_sg_dmabuf_ops_vmap,
 	.mmap = vb2_dma_sg_dmabuf_ops_mmap,
 	.release = vb2_dma_sg_dmabuf_ops_release,
-- 
2.25.0.265.gbab2e86ba0-goog

[PATCHv3 11/11] videobuf2: don't test db_attach in dma-contig prepare and finish

[Sergey Senozhatsky]

We moved cache management decision making to the upper layer and
rely on buffer's need_cache_sync flags and videobuf2 core. If the
upper layer (core) has decided to invoke ->prepare() or ->finish()
then we must sync.

For DMABUF ->need_cache_sync_on_prepare and ->need_cache_sync_on_flush
are always false so videobuf core does not call ->prepare() and
->finish() on such buffers.

Additionally, scratch the DMABUF comment.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 drivers/media/common/videobuf2/videobuf2-dma-contig.c | 6 ++----
 drivers/media/common/videobuf2/videobuf2-dma-sg.c     | 8 --------
 2 files changed, 2 insertions(+), 12 deletions(-)

diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
index a387260fb321..6ea0961149d7 100644
--- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c
+++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
@@ -100,8 +100,7 @@ static void vb2_dc_prepare(void *buf_priv)
 	struct vb2_dc_buf *buf = buf_priv;
 	struct sg_table *sgt = buf->dma_sgt;
 
-	/* DMABUF exporter will flush the cache for us */
-	if (!sgt || buf->db_attach)
+	if (!sgt)
 		return;
 
 	dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->orig_nents,
@@ -113,8 +112,7 @@ static void vb2_dc_finish(void *buf_priv)
 	struct vb2_dc_buf *buf = buf_priv;
 	struct sg_table *sgt = buf->dma_sgt;
 
-	/* DMABUF exporter will flush the cache for us */
-	if (!sgt || buf->db_attach)
+	if (!sgt)
 		return;
 
 	dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir);
diff --git a/drivers/media/common/videobuf2/videobuf2-dma-sg.c b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
index ddc67c9aaedb..2a01bc567321 100644
--- a/drivers/media/common/videobuf2/videobuf2-dma-sg.c
+++ b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
@@ -204,10 +204,6 @@ static void vb2_dma_sg_prepare(void *buf_priv)
 	struct vb2_dma_sg_buf *buf = buf_priv;
 	struct sg_table *sgt = buf->dma_sgt;
 
-	/* DMABUF exporter will flush the cache for us */
-	if (buf->db_attach)
-		return;
-
 	dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->orig_nents,
 			       buf->dma_dir);
 }
@@ -217,10 +213,6 @@ static void vb2_dma_sg_finish(void *buf_priv)
 	struct vb2_dma_sg_buf *buf = buf_priv;
 	struct sg_table *sgt = buf->dma_sgt;
 
-	/* DMABUF exporter will flush the cache for us */
-	if (buf->db_attach)
-		return;
-
 	dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir);
 }
 
-- 
2.25.0.265.gbab2e86ba0-goog

Re: [PATCHv3 01/11] videobuf2: add cache management members

[Hans Verkuil]

On 2/26/20 12:15 PM, Sergey Senozhatsky wrote:
> Extend vb2_buffer and vb2_queue structs with cache management
> members.
> 
> V4L2 UAPI already contains two buffer flags which user-space,
> supposedly, can use to control buffer cache sync:
> 
> - V4L2_BUF_FLAG_NO_CACHE_INVALIDATE
> - V4L2_BUF_FLAG_NO_CACHE_CLEAN
> 
> None of these, however, do anything at the moment. This patch
> set is intended to change it.
> 
> Since user-space cache management hints are supposed to be
> implemented on a per-buffer basis we need to extend vb2_buffer
> struct with two new memebers ->need_cache_sync_on_prepare and

memebers -> members

Regards,

	Hans

> ->need_cache_sync_on_finish, which will store corresponding
> user-space hints.
> 
> In order to preserve the existing behaviour, user-space cache
> managements flags will be handled only by those drivers that
> permit user-space cache hints. That's the purpose of vb2_queue
> ->allow_cache_hints member. Driver must set ->allow_cache_hints
> during queue initialisation to enable cache management hints
> mechanism.
> 
> Only drivers that set ->allow_cache_hints during queue initialisation
> will handle user-space cache management hints. Otherwise hints
> will be ignored.
> 
> Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> ---
>  include/media/videobuf2-core.h | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index a2b2208b02da..4a19170672ac 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -263,6 +263,10 @@ struct vb2_buffer {
>  	 *			after the 'buf_finish' op is called.
>  	 * copied_timestamp:	the timestamp of this capture buffer was copied
>  	 *			from an output buffer.
> +	 * need_cache_sync_on_prepare: when set buffer's ->prepare() function
> +	 *			performs cache sync/invalidation.
> +	 * need_cache_sync_on_finish: when set buffer's ->finish() function
> +	 *			performs cache sync/invalidation.
>  	 * queued_entry:	entry on the queued buffers list, which holds
>  	 *			all buffers queued from userspace
>  	 * done_entry:		entry on the list that stores all buffers ready
> @@ -273,6 +277,8 @@ struct vb2_buffer {
>  	unsigned int		synced:1;
>  	unsigned int		prepared:1;
>  	unsigned int		copied_timestamp:1;
> +	unsigned int		need_cache_sync_on_prepare:1;
> +	unsigned int		need_cache_sync_on_finish:1;
>  
>  	struct vb2_plane	planes[VB2_MAX_PLANES];
>  	struct list_head	queued_entry;
> @@ -491,6 +497,9 @@ struct vb2_buf_ops {
>   * @uses_requests: requests are used for this queue. Set to 1 the first time
>   *		a request is queued. Set to 0 when the queue is canceled.
>   *		If this is 1, then you cannot queue buffers directly.
> + * @allow_cache_hints: when set user-space can pass cache management hints in
> + * 		order to skip cache flush/invalidation on ->prepare() or/and
> + * 		->finish().
>   * @lock:	pointer to a mutex that protects the &struct vb2_queue. The
>   *		driver can set this to a mutex to let the v4l2 core serialize
>   *		the queuing ioctls. If the driver wants to handle locking
> @@ -564,6 +573,7 @@ struct vb2_queue {
>  	unsigned			requires_requests:1;
>  	unsigned			uses_qbuf:1;
>  	unsigned			uses_requests:1;
> +	unsigned			allow_cache_hints:1;
>  
>  	struct mutex			*lock;
>  	void				*owner;
> 

Re: [PATCHv3 02/11] videobuf2: handle V4L2 buffer cache flags

[Hans Verkuil]

On 2/26/20 12:15 PM, Sergey Senozhatsky wrote:
> Set video buffer cache management flags corresponding to V4L2 cache
> flags.
> 
> Both ->prepare() and ->finish() cache management hints should be
> passed during this stage (buffer preparation), because there is no
> other way for user-space to skip ->finish() cache flush.
> 
> There are two possible alternative approaches:
> - The first one is to move cache sync from ->finish() to dqbuf().
>   But this breaks some drivers, that need to fix-up buffers before
>   dequeueing them.
> 
> - The second one is to move ->finish() call from ->done() to dqbuf.

It's not clear what the purpose is of describing these alternative approaches.
I'd just drop that. It's a bit confusing.

> 
> Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> ---
>  .../media/common/videobuf2/videobuf2-v4l2.c   | 49 +++++++++++++++++++
>  include/media/videobuf2-core.h                | 11 +++++
>  2 files changed, 60 insertions(+)
> 
> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> index eb5d5db96552..2a604bd7793a 100644
> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> @@ -199,6 +199,15 @@ static int vb2_fill_vb2_v4l2_buffer(struct vb2_buffer *vb, struct v4l2_buffer *b
>  	vbuf->request_fd = -1;
>  	vbuf->is_held = false;
>  
> +	/*
> +	 * Clear buffer cache flags if queue does not support user space hints.
> +	 * That's to indicate to userspace that these flags won't work.
> +	 */
> +	if (!vb2_queue_allows_cache_hints(q)) {
> +		b->flags &= ~V4L2_BUF_FLAG_NO_CACHE_INVALIDATE;
> +		b->flags &= ~V4L2_BUF_FLAG_NO_CACHE_CLEAN;
> +	}
> +
>  	if (V4L2_TYPE_IS_MULTIPLANAR(b->type)) {
>  		switch (b->memory) {
>  		case VB2_MEMORY_USERPTR:
> @@ -337,6 +346,45 @@ static int vb2_fill_vb2_v4l2_buffer(struct vb2_buffer *vb, struct v4l2_buffer *b
>  	return 0;
>  }
>  
> +static void set_buffer_cache_hints(struct vb2_queue *q,
> +				   struct vb2_buffer *vb,
> +				   struct v4l2_buffer *b)
> +{
> +	/*
> +	 * DMA exporter should take care of cache syncs, so we can avoid
> +	 * explicit ->prepare()/->finish() syncs. For other ->memory types
> +	 * we always need ->prepare() or/and ->finish() cache sync.
> +	 */
> +	if (q->memory == VB2_MEMORY_DMABUF) {
> +		vb->need_cache_sync_on_finish = 0;
> +		vb->need_cache_sync_on_prepare = 0;
> +		return;
> +	}
> +
> +	/*
> +	 * Cache sync/invalidation flags are set by default in order to
> +	 * preserve existing behaviour for old apps/drivers.
> +	 */
> +	vb->need_cache_sync_on_prepare = 1;
> +	vb->need_cache_sync_on_finish = 1;
> +
> +	if (!vb2_queue_allows_cache_hints(q))
> +		return;
> +
> +	/*
> +	 * ->finish() cache sync can be avoided when queue direction is
> +	 * TO_DEVICE.
> +	 */
> +	if (q->dma_dir == DMA_TO_DEVICE)
> +		vb->need_cache_sync_on_finish = 0;
> +
> +	if (b->flags & V4L2_BUF_FLAG_NO_CACHE_INVALIDATE)
> +		vb->need_cache_sync_on_finish = 0;
> +
> +	if (b->flags & V4L2_BUF_FLAG_NO_CACHE_CLEAN)
> +		vb->need_cache_sync_on_prepare = 0;
> +}
> +
>  static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct media_device *mdev,
>  				    struct v4l2_buffer *b, bool is_prepare,
>  				    struct media_request **p_req)
> @@ -381,6 +429,7 @@ static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct media_device *md
>  	}
>  
>  	if (!vb->prepared) {
> +		set_buffer_cache_hints(q, vb, b);
>  		/* Copy relevant information provided by the userspace */
>  		memset(vbuf->planes, 0,
>  		       sizeof(vbuf->planes[0]) * vb->num_planes);
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index 4a19170672ac..d307869bfb15 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -632,6 +632,17 @@ struct vb2_queue {
>  #endif
>  };
>  
> +/**
> + * vb2_queue_allows_cache_hints() - Return true if the queue allows cache
> + * and memory consistency hints.
> + *
> + * @q:		pointer to &struct vb2_queue with videobuf2 queue
> + */
> +static inline bool vb2_queue_allows_cache_hints(struct vb2_queue *q)
> +{
> +	return (q->allow_cache_hints != 0) && (q->memory == VB2_MEMORY_MMAP);

Simply to:

	return q->allow_cache_hints && q->memory == VB2_MEMORY_MMAP;

Regards,

	Hans

> +}
> +
>  /**
>   * vb2_plane_vaddr() - Return a kernel virtual address of a given plane.
>   * @vb:		pointer to &struct vb2_buffer to which the plane in
> 

Re: [PATCHv3 03/11] videobuf2: add V4L2_FLAG_MEMORY_NON_CONSISTENT flag

[Hans Verkuil]

On 2/26/20 12:15 PM, Sergey Senozhatsky wrote:
> By setting or clearing V4L2_FLAG_MEMORY_NON_CONSISTENT flag
> user-space should be able to set or clear queue's NON_CONSISTENT
> ->dma_attrs. Queue's ->dma_attrs are passed to the underlying
> allocator in __vb2_buf_mem_alloc(), so thus user-space is able
> to request vb2 buffer's memory to be either consistent (coherent)
> or non-consistent.
> 
> The patch set also adds a corresponding capability flag:
> fill_buf_caps() reports V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS when
> queue supports user-space cache management hints.
> 
> Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> ---
>  Documentation/media/uapi/v4l/buffer.rst       | 29 +++++++++++++++++++
>  .../media/uapi/v4l/vidioc-reqbufs.rst         |  7 +++++
>  .../media/common/videobuf2/videobuf2-v4l2.c   |  2 ++
>  include/uapi/linux/videodev2.h                |  3 ++
>  4 files changed, 41 insertions(+)
> 
> diff --git a/Documentation/media/uapi/v4l/buffer.rst b/Documentation/media/uapi/v4l/buffer.rst
> index 3112300c2fa0..6b629ac59bf2 100644
> --- a/Documentation/media/uapi/v4l/buffer.rst
> +++ b/Documentation/media/uapi/v4l/buffer.rst
> @@ -681,6 +681,35 @@ Buffer Flags
>  
>      \normalsize
>  
> +.. _memory-flags:
> +
> +Memory Consistency Flags
> +========================
> +
> +.. tabularcolumns:: |p{7.0cm}|p{2.2cm}|p{8.3cm}|
> +
> +.. cssclass:: longtable
> +
> +.. flat-table::
> +    :header-rows:  0
> +    :stub-columns: 0
> +    :widths:       3 1 4
> +
> +    * .. _`V4L2_FLAG_MEMORY_NON_CONSISTENT`:
> +
> +      - ``V4L2_FLAG_MEMORY_NON_CONSISTENT``
> +      - 0x00000001
> +      - vb2 buffer is allocated either in consistent (it will be automatically

vb2 -> A

(vb2 is a kAPI term, and shouldn't be used in uAPI documentation)

> +	coherent between CPU and bus) or non-consistent memory. The latter

CPU and bus -> the CPU and the bus

> +	can provide performance gains, for instance CPU cache sync/flush

CPU -> the CPU

> +	operations can be avoided if the buffer is accessed by the corresponding
> +	device only and CPU does not read/write to/from that buffer. However,

CPU -> the CPU

> +	this requires extra care from the driver -- it must guarantee memory
> +	consistency by issuing cache flush/sync when consistency is needed.

cache -> a cache

> +	If this flag is set V4L2 will attempt to allocate vb2 buffer in

vb2 -> the

> +	non-consistent memory. The flag takes effect only if the buffer is
> +	used for :ref:`memory mapping <mmap>` I/O and the queue reports

reports -> reports the

> +	:ref:`V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS` capability.
>  
>  .. c:type:: v4l2_memory
>  
> diff --git a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
> index d0c643db477a..917df6fb6486 100644
> --- a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
> +++ b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
> @@ -156,6 +156,13 @@ aborting or finishing any DMA in progress, an implicit
>        - Only valid for stateless decoders. If set, then userspace can set the
>          ``V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF`` flag to hold off on returning the
>  	capture buffer until the OUTPUT timestamp changes.
> +    * - ``V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS``
> +      - 0x00000040
> +      - Set when the queue/buffer support memory consistency and cache

support -> supports

> +        management hints. See :ref:`V4L2_FLAG_MEMORY_NON_CONSISTENT`,
> +        :ref:`V4L2_BUF_FLAG_NO_CACHE_INVALIDATE` and
> +        :ref:`V4L2_BUF_FLAG_NO_CACHE_CLEAN`.
> +
>  
>  Return Value
>  ============
> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> index 2a604bd7793a..f91cba37e223 100644
> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> @@ -711,6 +711,8 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
>  		*caps |= V4L2_BUF_CAP_SUPPORTS_DMABUF;
>  	if (q->subsystem_flags & VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF)
>  		*caps |= V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF;
> +	if ((q->allow_cache_hints != 0) && (q->io_modes & VB2_MMAP))

Just say:

	if (q->allow_cache_hints && (q->io_modes & VB2_MMAP))

Regards,

	Hans

> +		*caps |= V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS;
>  #ifdef CONFIG_MEDIA_CONTROLLER_REQUEST_API
>  	if (q->supports_requests)
>  		*caps |= V4L2_BUF_CAP_SUPPORTS_REQUESTS;
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 5f9357dcb060..e92c29864730 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -189,6 +189,8 @@ enum v4l2_memory {
>  	V4L2_MEMORY_DMABUF           = 4,
>  };
>  
> +#define V4L2_FLAG_MEMORY_NON_CONSISTENT		(1 << 0)
> +
>  /* see also http://vektor.theorem.ca/graphics/ycbcr/ */
>  enum v4l2_colorspace {
>  	/*
> @@ -946,6 +948,7 @@ struct v4l2_requestbuffers {
>  #define V4L2_BUF_CAP_SUPPORTS_REQUESTS			(1 << 3)
>  #define V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS		(1 << 4)
>  #define V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF	(1 << 5)
> +#define V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS		(1 << 6)
>  
>  /**
>   * struct v4l2_plane - plane info for multi-planar buffers
> 

Re: [PATCHv3 05/11] videobuf2: handle V4L2_FLAG_MEMORY_NON_CONSISTENT flag

[Hans Verkuil]

On 2/26/20 12:15 PM, Sergey Senozhatsky wrote:
> This patch lets user-space to request a non-consistent memory
> allocation during CREATE_BUFS and REQBUFS ioctl calls.
> 
> = CREATE_BUFS
> 
>   struct v4l2_create_buffers has seven 4-byte reserved areas,
>   so reserved[0] is renamed to ->flags. The struct, thus, now
>   has six reserved 4-byte regions.
> 
> = REQBUFS
> 
>  We use one bit of a ->reserved[1] member of struct v4l2_requestbuffers,
>  which is now renamed to ->flags. Unlike v4l2_create_buffers, struct
>  v4l2_requestbuffers does not have enough reserved room. Therefore for
>  backward compatibility  ->reserved and ->flags were put into anonymous
>  union.
> 
> Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> ---
>  .../media/uapi/v4l/vidioc-create-bufs.rst     |  8 ++++-
>  .../media/uapi/v4l/vidioc-reqbufs.rst         | 15 +++++++--
>  .../media/common/videobuf2/videobuf2-v4l2.c   | 31 +++++++++++++++++--
>  drivers/media/v4l2-core/v4l2-ioctl.c          |  5 +--
>  include/uapi/linux/videodev2.h                |  8 +++--
>  5 files changed, 54 insertions(+), 13 deletions(-)
> 
> diff --git a/Documentation/media/uapi/v4l/vidioc-create-bufs.rst b/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
> index bd08e4f77ae4..6a8a4d5de2f1 100644
> --- a/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
> +++ b/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
> @@ -121,7 +121,13 @@ than the number requested.
>  	other changes, then set ``count`` to 0, ``memory`` to
>  	``V4L2_MEMORY_MMAP`` and ``format.type`` to the buffer type.
>      * - __u32
> -      - ``reserved``\ [7]
> +      - ``flags``
> +      - Specifies additional buffer management attributes.
> +	See :ref:`memory-flags`. Old drivers and applications must set it to
> +	zero.

Drop the last sentence, it's not relevant.

> +
> +    * - __u32
> +      - ``reserved``\ [6]
>        - A place holder for future extensions. Drivers and applications
>  	must set the array to zero.

Old drivers and applications still think reserved is [7] and will zero this.

>  
> diff --git a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
> index 917df6fb6486..e52cc4401fba 100644
> --- a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
> +++ b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
> @@ -112,10 +112,19 @@ aborting or finishing any DMA in progress, an implicit
>  	``V4L2_MEMORY_MMAP`` and ``type`` set to the buffer type. This will
>  	free any previously allocated buffers, so this is typically something
>  	that will be done at the start of the application.
> -    * - __u32
> +    * - union
> +      - (anonymous)

Anonymous unions are formatted a bit differently (I made a very recent patch
that unified the union formatting in the v4l docs). See e.g.
Documentation/media/uapi/v4l/vidioc-g-ext-ctrls.rst.

> +    * -
> +      - __u32
> +      - ``flags``\ [1]
> +      - Specifies additional buffer management attributes.
> +	See :ref:`memory-flags`. Old drivers and applications must set it to
> +	zero.

Ditto.

> +
> +    * -
> +      - __u32
>        - ``reserved``\ [1]
> -      - A place holder for future extensions. Drivers and applications
> -	must set the array to zero.
> +      - Kept for backwards compatibility. Use ``flags`` instead.
>  
>  .. tabularcolumns:: |p{6.1cm}|p{2.2cm}|p{8.7cm}|
>  
> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> index cc31629c06dc..4954c9fc678d 100644
> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> @@ -722,9 +722,18 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
>  int vb2_reqbufs(struct vb2_queue *q, struct v4l2_requestbuffers *req)
>  {
>  	int ret = vb2_verify_memory_type(q, req->memory, req->type);
> +	bool consistent = true;
> +
> +	if (!vb2_queue_allows_cache_hints(q))
> +		req->flags &= ~V4L2_FLAG_MEMORY_NON_CONSISTENT;
> +
> +	if (req->flags & V4L2_FLAG_MEMORY_NON_CONSISTENT)
> +		consistent = false;
>  
>  	fill_buf_caps(q, &req->capabilities);
> -	return ret ? ret : vb2_core_reqbufs(q, req->memory, true, &req->count);
> +	if (ret)
> +		return ret;
> +	return vb2_core_reqbufs(q, req->memory, consistent, &req->count);
>  }
>  EXPORT_SYMBOL_GPL(vb2_reqbufs);
>  
> @@ -753,6 +762,7 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
>  	unsigned requested_sizes[VIDEO_MAX_PLANES];
>  	struct v4l2_format *f = &create->format;
>  	int ret = vb2_verify_memory_type(q, create->memory, f->type);
> +	bool consistent = true;
>  	unsigned i;
>  
>  	fill_buf_caps(q, &create->capabilities);
> @@ -798,7 +808,14 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
>  	for (i = 0; i < requested_planes; i++)
>  		if (requested_sizes[i] == 0)
>  			return -EINVAL;
> -	return ret ? ret : vb2_core_create_bufs(q, create->memory, true,
> +
> +	if (!vb2_queue_allows_cache_hints(q))
> +		create->flags &= ~V4L2_FLAG_MEMORY_NON_CONSISTENT;
> +
> +	if (create->flags & V4L2_FLAG_MEMORY_NON_CONSISTENT)
> +		consistent = false;
> +
> +	return ret ? ret : vb2_core_create_bufs(q, create->memory, consistent,
>  		&create->count, requested_planes, requested_sizes);
>  }
>  EXPORT_SYMBOL_GPL(vb2_create_bufs);
> @@ -968,13 +985,21 @@ int vb2_ioctl_reqbufs(struct file *file, void *priv,
>  {
>  	struct video_device *vdev = video_devdata(file);
>  	int res = vb2_verify_memory_type(vdev->queue, p->memory, p->type);
> +	bool consistent = true;
>  
>  	fill_buf_caps(vdev->queue, &p->capabilities);
>  	if (res)
>  		return res;
>  	if (vb2_queue_is_busy(vdev, file))
>  		return -EBUSY;
> -	res = vb2_core_reqbufs(vdev->queue, p->memory, true, &p->count);
> +
> +	if (!vb2_queue_allows_cache_hints(vdev->queue))
> +		p->flags &= ~V4L2_FLAG_MEMORY_NON_CONSISTENT;
> +
> +	if (p->flags & V4L2_FLAG_MEMORY_NON_CONSISTENT)
> +		consistent = false;
> +
> +	res = vb2_core_reqbufs(vdev->queue, p->memory, consistent, &p->count);
>  	/* If count == 0, then the owner has released all buffers and he
>  	   is no longer owner of the queue. Otherwise we have a new owner. */
>  	if (res == 0)
> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> index fbcc7a20eedf..53b87bfd50d7 100644
> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> @@ -1973,9 +1973,6 @@ static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,
>  
>  	if (ret)
>  		return ret;
> -
> -	CLEAR_AFTER_FIELD(p, capabilities);
> -
>  	return ops->vidioc_reqbufs(file, fh, p);
>  }
>  
> @@ -2015,7 +2012,7 @@ static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
>  	if (ret)
>  		return ret;
>  
> -	CLEAR_AFTER_FIELD(create, capabilities);
> +	CLEAR_AFTER_FIELD(create, flags);
>  
>  	v4l_sanitize_format(&create->format);
>  
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index e92c29864730..12b1bd220347 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -938,7 +938,10 @@ struct v4l2_requestbuffers {
>  	__u32			type;		/* enum v4l2_buf_type */
>  	__u32			memory;		/* enum v4l2_memory */
>  	__u32			capabilities;
> -	__u32			reserved[1];
> +	union {
> +		__u32		flags;
> +		__u32		reserved[1];
> +	};
>  };
>  
>  /* capabilities for struct v4l2_requestbuffers and v4l2_create_buffers */
> @@ -2446,7 +2449,8 @@ struct v4l2_create_buffers {
>  	__u32			memory;
>  	struct v4l2_format	format;
>  	__u32			capabilities;
> -	__u32			reserved[7];
> +	__u32			flags;
> +	__u32			reserved[6];
>  };
>  
>  /*
> 

Regards,

	Hans

Re: [PATCHv3 00/11] Implement V4L2_BUF_FLAG_NO_CACHE_* flags

[Hans Verkuil]

On 2/26/20 12:15 PM, Sergey Senozhatsky wrote:
> Hello,
> 
> 	V3 of the patchset, reshuffled and updated.
> 
> - Most notable changes:
> 
> a) Added a simple helper function vb2_queue_allows_cache_hints(),
>    which return true if queue has ->allow_cache_hints and when
>    ->memory is VB2_MEMORY_MMAP.
>    That is - user space cache and memory consistency hints are now
>    specifically for MMAP buffers and queues that support hints.
> 
> b) Set V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS capability bit only when queue
>    has ->allow_cache_hints and ->io_modes has VB2_MMAP bit set
> 
> c) Clear "incompatible" request's flags when queue does not permit
>    cache and memory consistency hints (IOW, when vb2_queue_allows_cache_hints()
>    return false)
> 
> 
> Minor changes:
> 
> - Squashed V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS and V4L2_FLAG_MEMORY_NON_CONSISTENT
>   patches.
> 
> - Added more documentation and code comments.
> 
> 
> Previous series:
> v2 link: https://lore.kernel.org/lkml/20200204025641.218376-1-senozhatsky@chromium.org/
> v1 link: https://lore.kernel.org/lkml/20191217032034.54897-1-senozhatsky@chromium.org/
> 
> 
> Series Intro
> ========================================================================
> 
>         This is a reworked version of the vb2 cache hints
> (V4L2_BUF_FLAG_NO_CACHE_INVALIDATE / V4L2_BUF_FLAG_NO_CACHE_CLEAN)
> support patch series which previsouly was developed by Sakari and
> Laurent [0].
> 
> The patch set attempts to preserve the existing behvaiour - cache
> sync is performed in ->prepare() and ->finish() (unless the buffer
> is DMA exported). User space can request “default behavior” override
> with cache management hints, which are handled on a per-buffer basis
> and should be supplied with v4l2_buffer ->flags during buffer
> preparation. There are two possible hints:
> 
> - V4L2_BUF_FLAG_NO_CACHE_INVALIDATE
>         No cache sync on ->finish()
> 
> - V4L2_BUF_FLAG_NO_CACHE_CLEAN
>         No cache sync on ->prepare()
> 
> In order to keep things on the safe side, we also require driver
> to explicitly state which of its queues (if any) support user space
> cache management hints (such queues should have ->allow_cache_hints
> bit set).
> 
> The patch set also (to some extent) simplifies allocators' ->prepare()
> and ->finish() callbacks. Namely, we move cache management decision
> making to the upper - core - layer. For example, if, previously, we
> would have something like this
> 
>         vb2_buffer_done()
>           vb2_dc_finish()
>             if (buf->db_attach)
>                return;
> 
> where each allocators' ->finish() callback would either bail
> out (DMA exported buffer, for instance) or sync, now that "bail
> out or sync" decision is made before we call into the allocator.
> 
> Along with cache management hints, user space is also able to
> adjust queue's memory consistency attributes. Memory consistency
> attribute (dma_attrs) is per-queue, yet it plays its role on the
> allocator level, when we allocate buffers’ private memory (planes).
> For the time being, only one consistency attribute is supported:
> DMA_ATTR_NON_CONSISTENT.

v3 looks very good, I only found some minor issues.

I think v4 should be ready to be merged, unless others have more comments.

Regards,

	Hans

> 
> [0] https://www.mail-archive.com/linux-media@vger.kernel.org/msg112459.html
> 
> Sergey Senozhatsky (11):
>   videobuf2: add cache management members
>   videobuf2: handle V4L2 buffer cache flags
>   videobuf2: add V4L2_FLAG_MEMORY_NON_CONSISTENT flag
>   videobuf2: add queue memory consistency parameter
>   videobuf2: handle V4L2_FLAG_MEMORY_NON_CONSISTENT flag
>   videobuf2: factor out planes prepare/finish functions
>   videobuf2: do not sync caches when we are allowed not to
>   videobuf2: check ->synced flag in prepare() and finish()
>   videobuf2: add begin/end cpu_access callbacks to dma-contig
>   videobuf2: add begin/end cpu_access callbacks to dma-sg
>   videobuf2: don't test db_attach in dma-contig prepare and finish
> 
>  Documentation/media/uapi/v4l/buffer.rst       |  29 +++++
>  .../media/uapi/v4l/vidioc-create-bufs.rst     |   8 +-
>  .../media/uapi/v4l/vidioc-reqbufs.rst         |  22 +++-
>  .../media/common/videobuf2/videobuf2-core.c   | 110 +++++++++++++-----
>  .../common/videobuf2/videobuf2-dma-contig.c   |  39 ++++++-
>  .../media/common/videobuf2/videobuf2-dma-sg.c |  36 ++++--
>  .../media/common/videobuf2/videobuf2-v4l2.c   |  82 ++++++++++++-
>  drivers/media/dvb-core/dvb_vb2.c              |   2 +-
>  drivers/media/v4l2-core/v4l2-ioctl.c          |   5 +-
>  include/media/videobuf2-core.h                |  28 ++++-
>  include/uapi/linux/videodev2.h                |  11 +-
>  11 files changed, 314 insertions(+), 58 deletions(-)
> 

Re: [PATCHv3 02/11] videobuf2: handle V4L2 buffer cache flags

[Sergey Senozhatsky]

On (20/02/27 12:58), Hans Verkuil wrote:
[..]
> > There are two possible alternative approaches:
> > - The first one is to move cache sync from ->finish() to dqbuf().
> >   But this breaks some drivers, that need to fix-up buffers before
> >   dequeueing them.
> > 
> > - The second one is to move ->finish() call from ->done() to dqbuf.
> 
> It's not clear what the purpose is of describing these alternative approaches.
> I'd just drop that. It's a bit confusing.

OK.

> > +/**
> > + * vb2_queue_allows_cache_hints() - Return true if the queue allows cache
> > + * and memory consistency hints.
> > + *
> > + * @q:		pointer to &struct vb2_queue with videobuf2 queue
> > + */
> > +static inline bool vb2_queue_allows_cache_hints(struct vb2_queue *q)
> > +{
> > +	return (q->allow_cache_hints != 0) && (q->memory == VB2_MEMORY_MMAP);
> 
> Simply to:
> 
> 	return q->allow_cache_hints && q->memory == VB2_MEMORY_MMAP;
> 

OK. I saw vb2_is_busy()

static inline bool vb2_is_busy(struct vb2_queue *q)
{
	return (q->num_buffers > 0);
}

in the very same header file and concluded that maybe this is the
preferred style.

	-ss

Re: [PATCHv3 01/11] videobuf2: add cache management members

[Sergey Senozhatsky]

On (20/02/27 12:55), Hans Verkuil wrote:
> On 2/26/20 12:15 PM, Sergey Senozhatsky wrote:
> > Extend vb2_buffer and vb2_queue structs with cache management
> > members.
> > 
> > V4L2 UAPI already contains two buffer flags which user-space,
> > supposedly, can use to control buffer cache sync:
> > 
> > - V4L2_BUF_FLAG_NO_CACHE_INVALIDATE
> > - V4L2_BUF_FLAG_NO_CACHE_CLEAN
> > 
> > None of these, however, do anything at the moment. This patch
> > set is intended to change it.
> > 
> > Since user-space cache management hints are supposed to be
> > implemented on a per-buffer basis we need to extend vb2_buffer
> > struct with two new memebers ->need_cache_sync_on_prepare and
> 
> memebers -> members
> 

  meme bears  :)

	-ss

Re: [PATCHv3 05/11] videobuf2: handle V4L2_FLAG_MEMORY_NON_CONSISTENT flag

[Sergey Senozhatsky]

On (20/02/27 13:36), Hans Verkuil wrote:
> > diff --git a/Documentation/media/uapi/v4l/vidioc-create-bufs.rst b/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
> > index bd08e4f77ae4..6a8a4d5de2f1 100644
> > --- a/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
> > +++ b/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
> > @@ -121,7 +121,13 @@ than the number requested.
> >  	other changes, then set ``count`` to 0, ``memory`` to
> >  	``V4L2_MEMORY_MMAP`` and ``format.type`` to the buffer type.
> >      * - __u32
> > -      - ``reserved``\ [7]
> > +      - ``flags``
> > +      - Specifies additional buffer management attributes.
> > +	See :ref:`memory-flags`. Old drivers and applications must set it to
> > +	zero.
> 
> Drop the last sentence, it's not relevant.

OK.

> > +
> > +    * - __u32
> > +      - ``reserved``\ [6]
> >        - A place holder for future extensions. Drivers and applications
> >  	must set the array to zero.
> 
> Old drivers and applications still think reserved is [7] and will zero this.

OK.

Hmm... If those apps use hard-coded size then we might have a problem.
If they use sizeof(reserved) then everything is OK. Shall we also have
a union here?

> > diff --git a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
> > index 917df6fb6486..e52cc4401fba 100644
> > --- a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
> > +++ b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
> > @@ -112,10 +112,19 @@ aborting or finishing any DMA in progress, an implicit
> >  	``V4L2_MEMORY_MMAP`` and ``type`` set to the buffer type. This will
> >  	free any previously allocated buffers, so this is typically something
> >  	that will be done at the start of the application.
> > -    * - __u32
> > +    * - union
> > +      - (anonymous)
> 
> Anonymous unions are formatted a bit differently (I made a very recent patch
> that unified the union formatting in the v4l docs). See e.g.
> Documentation/media/uapi/v4l/vidioc-g-ext-ctrls.rst.

OK, will take a look.

	-ss

Re: [PATCHv3 03/11] videobuf2: add V4L2_FLAG_MEMORY_NON_CONSISTENT flag

[Sergey Senozhatsky]

On (20/02/27 13:25), Hans Verkuil wrote:
[..]
> > +      - vb2 buffer is allocated either in consistent (it will be automatically
> 
> vb2 -> A
> 
> (vb2 is a kAPI term, and shouldn't be used in uAPI documentation)
> 
> > +	coherent between CPU and bus) or non-consistent memory. The latter
> 
> CPU and bus -> the CPU and the bus
> 
> > +	can provide performance gains, for instance CPU cache sync/flush
> 
> CPU -> the CPU
> 
> > +	operations can be avoided if the buffer is accessed by the corresponding
> > +	device only and CPU does not read/write to/from that buffer. However,
> 
> CPU -> the CPU
> 
> > +	this requires extra care from the driver -- it must guarantee memory
> > +	consistency by issuing cache flush/sync when consistency is needed.
> 
> cache -> a cache
> 
> > +	If this flag is set V4L2 will attempt to allocate vb2 buffer in
> 
> vb2 -> the
> 
> > +	non-consistent memory. The flag takes effect only if the buffer is
> > +	used for :ref:`memory mapping <mmap>` I/O and the queue reports
> 
> reports -> reports the

OK.

> > +++ b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
> > @@ -156,6 +156,13 @@ aborting or finishing any DMA in progress, an implicit
> >        - Only valid for stateless decoders. If set, then userspace can set the
> >          ``V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF`` flag to hold off on returning the
> >  	capture buffer until the OUTPUT timestamp changes.
> > +    * - ``V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS``
> > +      - 0x00000040
> > +      - Set when the queue/buffer support memory consistency and cache
> 
> support -> supports

OK.

> > +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> > @@ -711,6 +711,8 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
> >  		*caps |= V4L2_BUF_CAP_SUPPORTS_DMABUF;
> >  	if (q->subsystem_flags & VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF)
> >  		*caps |= V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF;
> > +	if ((q->allow_cache_hints != 0) && (q->io_modes & VB2_MMAP))
> 
> Just say:
> 
> 	if (q->allow_cache_hints && (q->io_modes & VB2_MMAP))

OK.

	-ss

Re: [PATCHv3 05/11] videobuf2: handle V4L2_FLAG_MEMORY_NON_CONSISTENT flag

[Sergey Senozhatsky]

On (20/02/27 13:36), Hans Verkuil wrote:
[..]
> >  	other changes, then set ``count`` to 0, ``memory`` to
> >  	``V4L2_MEMORY_MMAP`` and ``format.type`` to the buffer type.
> >      * - __u32
> > -      - ``reserved``\ [7]
> > +      - ``flags``
> > +      - Specifies additional buffer management attributes.
> > +	See :ref:`memory-flags`. Old drivers and applications must set it to
> > +	zero.
> 
> Drop the last sentence, it's not relevant.
> 
> > +
> > +    * - __u32
> > +      - ``reserved``\ [6]
> >        - A place holder for future extensions. Drivers and applications
> >  	must set the array to zero.
> 
> Old drivers and applications still think reserved is [7] and will zero this.

Just to make sure, does this mean that you also want me to drop the
"Drivers and applications must set the array to zero" sentence?

	-ss

Re: [PATCHv3 05/11] videobuf2: handle V4L2_FLAG_MEMORY_NON_CONSISTENT flag

[Hans Verkuil]

On 2/28/20 2:38 AM, Sergey Senozhatsky wrote:
> On (20/02/27 13:36), Hans Verkuil wrote:
>>> diff --git a/Documentation/media/uapi/v4l/vidioc-create-bufs.rst b/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
>>> index bd08e4f77ae4..6a8a4d5de2f1 100644
>>> --- a/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
>>> +++ b/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
>>> @@ -121,7 +121,13 @@ than the number requested.
>>>  	other changes, then set ``count`` to 0, ``memory`` to
>>>  	``V4L2_MEMORY_MMAP`` and ``format.type`` to the buffer type.
>>>      * - __u32
>>> -      - ``reserved``\ [7]
>>> +      - ``flags``
>>> +      - Specifies additional buffer management attributes.
>>> +	See :ref:`memory-flags`. Old drivers and applications must set it to
>>> +	zero.
>>
>> Drop the last sentence, it's not relevant.
> 
> OK.
> 
>>> +
>>> +    * - __u32
>>> +      - ``reserved``\ [6]
>>>        - A place holder for future extensions. Drivers and applications
>>>  	must set the array to zero.
>>
>> Old drivers and applications still think reserved is [7] and will zero this.
> 
> OK.
> 
> Hmm... If those apps use hard-coded size then we might have a problem.
> If they use sizeof(reserved) then everything is OK. Shall we also have
> a union here?

No, apps will use sizeof(reserved).

Regards,

	Hans

> 
>>> diff --git a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
>>> index 917df6fb6486..e52cc4401fba 100644
>>> --- a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
>>> +++ b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
>>> @@ -112,10 +112,19 @@ aborting or finishing any DMA in progress, an implicit
>>>  	``V4L2_MEMORY_MMAP`` and ``type`` set to the buffer type. This will
>>>  	free any previously allocated buffers, so this is typically something
>>>  	that will be done at the start of the application.
>>> -    * - __u32
>>> +    * - union
>>> +      - (anonymous)
>>
>> Anonymous unions are formatted a bit differently (I made a very recent patch
>> that unified the union formatting in the v4l docs). See e.g.
>> Documentation/media/uapi/v4l/vidioc-g-ext-ctrls.rst.
> 
> OK, will take a look.
> 
> 	-ss
> 

Re: [PATCHv3 05/11] videobuf2: handle V4L2_FLAG_MEMORY_NON_CONSISTENT flag

[Hans Verkuil]

On 2/28/20 4:57 AM, Sergey Senozhatsky wrote:
> On (20/02/27 13:36), Hans Verkuil wrote:
> [..]
>>>  	other changes, then set ``count`` to 0, ``memory`` to
>>>  	``V4L2_MEMORY_MMAP`` and ``format.type`` to the buffer type.
>>>      * - __u32
>>> -      - ``reserved``\ [7]
>>> +      - ``flags``
>>> +      - Specifies additional buffer management attributes.
>>> +	See :ref:`memory-flags`. Old drivers and applications must set it to
>>> +	zero.
>>
>> Drop the last sentence, it's not relevant.
>>
>>> +
>>> +    * - __u32
>>> +      - ``reserved``\ [6]
>>>        - A place holder for future extensions. Drivers and applications
>>>  	must set the array to zero.
>>
>> Old drivers and applications still think reserved is [7] and will zero this.
> 
> Just to make sure, does this mean that you also want me to drop the
> "Drivers and applications must set the array to zero" sentence?

Not for the reserved field, only for the flags field.

Regards,

	Hans

> 
> 	-ss
> 

Re: [PATCHv3 05/11] videobuf2: handle V4L2_FLAG_MEMORY_NON_CONSISTENT flag

[Sergey Senozhatsky]

On (20/02/28 09:50), Hans Verkuil wrote:
> On 2/28/20 4:57 AM, Sergey Senozhatsky wrote:
> > On (20/02/27 13:36), Hans Verkuil wrote:
> > [..]
[..]
> >>> +    * - __u32
> >>> +      - ``reserved``\ [6]
> >>>        - A place holder for future extensions. Drivers and applications
> >>>  	must set the array to zero.
> >>
> >> Old drivers and applications still think reserved is [7] and will zero this.
> > 
> > Just to make sure, does this mean that you also want me to drop the
> > "Drivers and applications must set the array to zero" sentence?
> 
> Not for the reserved field, only for the flags field.

Got it.

So V4 is ready. Do you think it'll make sense to send it
out now or next week?

	-ss