[PATCH 01/17] media/v4l2: remove V4L2-FLAG-MEMORY-NON-CONSISTENT flag

Christoph Hellwig
2020-09-14T14:51:26Z

From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>

The patch partially reverts some of the UAPI bits of the buffer
cache management hints. Namely, the queue consistency (memory
coherency) user-space hint because, as it turned out, the kernel
implementation of this feature was misusing DMA_ATTR_NON_CONSISTENT.

The patch revers both kernel and user space parts: removes the
DMA consistency attr functions, rollbacks changes to v4l2_requestbuffers,
v4l2_create_buffers structures and corresponding UAPI functions
(plus compat32 layer) and cleanups the documentation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
.../userspace-api/media/v4l/buffer.rst | 17 -------
.../media/v4l/vidioc-create-bufs.rst | 6 +--
.../media/v4l/vidioc-reqbufs.rst | 12 +----
.../media/common/videobuf2/videobuf2-core.c | 46 +++----------------
.../common/videobuf2/videobuf2-dma-contig.c | 19 --------
.../media/common/videobuf2/videobuf2-dma-sg.c | 3 +-
.../media/common/videobuf2/videobuf2-v4l2.c | 18 +-------
drivers/media/v4l2-core/v4l2-compat-ioctl32.c | 10 +---
drivers/media/v4l2-core/v4l2-ioctl.c | 5 +-
include/media/videobuf2-core.h | 7 +--
include/uapi/linux/videodev2.h | 13 +-----
11 files changed, 22 insertions(+), 134 deletions(-)

diff --git a/Documentation/userspace-api/media/v4l/buffer.rst b/Documentation/userspace-api/media/v4l/buffer.rst
index 57e752aaf414a7..2044ed13cd9d7d 100644
--- a/Documentation/userspace-api/media/v4l/buffer.rst
+++ b/Documentation/userspace-api/media/v4l/buffer.rst
@@ -701,23 +701,6 @@ Memory Consistency Flags
:stub-columns: 0
:widths: 3 1 4

- * .. _`V4L2-FLAG-MEMORY-NON-CONSISTENT`:
-
- - ``V4L2_FLAG_MEMORY_NON_CONSISTENT``
- - 0x00000001
- - A buffer is allocated either in consistent (it will be automatically
- coherent between the CPU and the bus) or non-consistent memory. The
- latter can provide performance gains, for instance the CPU cache
- sync/flush operations can be avoided if the buffer is accessed by the
- corresponding device only and the CPU does not read/write to/from that
- buffer. However, this requires extra care from the driver -- it must
- guarantee memory consistency by issuing a cache flush/sync when
- consistency is needed. If this flag is set V4L2 will attempt to
- allocate the 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 the :ref:`V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS
- <V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS>` capability.
-
.. c:type:: v4l2_memory

enum v4l2_memory
diff --git a/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst b/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst
index f2a702870fadc1..12cf6b44f414f7 100644
--- a/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst
@@ -120,13 +120,9 @@ than the number requested.
If you want to just query the capabilities without making any
other changes, then set ``count`` to 0, ``memory`` to
``V4L2_MEMORY_MMAP`` and ``format.type`` to the buffer type.
- * - __u32
- - ``flags``
- - Specifies additional buffer management attributes.
- See :ref:`memory-flags`.

* - __u32
- - ``reserved``\ [6]
+ - ``reserved``\ [7]
- A place holder for future extensions. Drivers and applications
must set the array to zero.

diff --git a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
index 75d894d9c36c42..0e3e2fde65e850 100644
--- a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
@@ -112,17 +112,10 @@ 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.
- * - union {
- - (anonymous)
- * - __u32
- - ``flags``
- - Specifies additional buffer management attributes.
- See :ref:`memory-flags`.
* - __u32
- ``reserved``\ [1]
- - Kept for backwards compatibility. Use ``flags`` instead.
- * - }
- -
+ - A place holder for future extensions. Drivers and applications
+ must set the array to zero.

.. tabularcolumns:: |p{6.1cm}|p{2.2cm}|p{8.7cm}|

@@ -169,7 +162,6 @@ aborting or finishing any DMA in progress, an implicit
- This capability is set by the driver to indicate that the queue supports
cache and memory management hints. However, it's only valid when the
queue is used for :ref:`memory mapping <mmap>` streaming I/O. See
- :ref:`V4L2_FLAG_MEMORY_NON_CONSISTENT <V4L2-FLAG-MEMORY-NON-CONSISTENT>`,
:ref:`V4L2_BUF_FLAG_NO_CACHE_INVALIDATE <V4L2-BUF-FLAG-NO-CACHE-INVALIDATE>` and
:ref:`V4L2_BUF_FLAG_NO_CACHE_CLEAN <V4L2-BUF-FLAG-NO-CACHE-CLEAN>`.

diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index f544d3393e9d6b..4eab6d81cce170 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -721,39 +721,14 @@ 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)
-{
- q->dma_attrs &= ~DMA_ATTR_NON_CONSISTENT;
-
- if (!vb2_queue_allows_cache_hints(q))
- return;
- if (!consistent_mem)
- q->dma_attrs |= DMA_ATTR_NON_CONSISTENT;
-}
-
-static bool verify_consistency_attr(struct vb2_queue *q, bool consistent_mem)
-{
- bool queue_is_consistent = !(q->dma_attrs & DMA_ATTR_NON_CONSISTENT);
-
- if (consistent_mem != queue_is_consistent) {
- dprintk(q, 1, "memory consistency model mismatch\n");
- return false;
- }
- return true;
-}
-
int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
- unsigned int flags, unsigned int *count)
+ unsigned int *count)
{
unsigned int num_buffers, allocated_buffers, num_planes = 0;
unsigned plane_sizes[VB2_MAX_PLANES] = { };
- bool consistent_mem = true;
unsigned int i;
int ret;

- if (flags & V4L2_FLAG_MEMORY_NON_CONSISTENT)
- consistent_mem = false;
-
if (q->streaming) {
dprintk(q, 1, "streaming active\n");
return -EBUSY;
@@ -765,8 +740,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
}

if (*count == 0 || q->num_buffers != 0 ||
- (q->memory != VB2_MEMORY_UNKNOWN && q->memory != memory) ||
- !verify_consistency_attr(q, consistent_mem)) {
+ (q->memory != VB2_MEMORY_UNKNOWN && q->memory != memory)) {
/*
* We already have buffers allocated, so first check if they
* are not in use and can be freed.
@@ -803,7 +777,6 @@ 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.
@@ -888,18 +861,14 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
EXPORT_SYMBOL_GPL(vb2_core_reqbufs);

int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
- unsigned int flags, unsigned int *count,
+ unsigned int *count,
unsigned int requested_planes,
const unsigned int requested_sizes[])
{
unsigned int num_planes = 0, num_buffers, allocated_buffers;
unsigned plane_sizes[VB2_MAX_PLANES] = { };
- bool consistent_mem = true;
int ret;

- if (flags & V4L2_FLAG_MEMORY_NON_CONSISTENT)
- consistent_mem = false;
-
if (q->num_buffers == VB2_MAX_FRAME) {
dprintk(q, 1, "maximum number of buffers already allocated\n");
return -ENOBUFS;
@@ -912,15 +881,12 @@ 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(q, 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);
@@ -2581,7 +2547,7 @@ 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, 0, &fileio->count);
+ ret = vb2_core_reqbufs(q, fileio->memory, &fileio->count);
if (ret)
goto err_kfree;

@@ -2638,7 +2604,7 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)

err_reqbufs:
fileio->count = 0;
- vb2_core_reqbufs(q, fileio->memory, 0, &fileio->count);
+ vb2_core_reqbufs(q, fileio->memory, &fileio->count);

err_kfree:
q->fileio = NULL;
@@ -2658,7 +2624,7 @@ 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, 0, &fileio->count);
+ vb2_core_reqbufs(q, fileio->memory, &fileio->count);
kfree(fileio);
dprintk(q, 3, "file io emulator closed\n");
}
diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
index ec3446cc45b8da..7b1b86ec942d7d 100644
--- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c
+++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
@@ -42,11 +42,6 @@ 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 */
/*********************************************/
@@ -341,13 +336,6 @@ 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;
}

@@ -355,13 +343,6 @@ 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;
}

diff --git a/drivers/media/common/videobuf2/videobuf2-dma-sg.c b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
index 0a40e00f0d7e5c..a86fce5d8ea8bf 100644
--- a/drivers/media/common/videobuf2/videobuf2-dma-sg.c
+++ b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
@@ -123,8 +123,7 @@ static void *vb2_dma_sg_alloc(struct device *dev, unsigned long dma_attrs,
/*
* 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.
+ * attributes passed from the upper layer.
*/
buf->pages = kvmalloc_array(buf->num_pages, sizeof(struct page *),
GFP_KERNEL | __GFP_ZERO);
diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index 30caad27281e1a..cfe197df970df2 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -722,22 +722,12 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
#endif
}

-static void clear_consistency_attr(struct vb2_queue *q,
- int memory,
- unsigned int *flags)
-{
- if (!q->allow_cache_hints || memory != V4L2_MEMORY_MMAP)
- *flags &= ~V4L2_FLAG_MEMORY_NON_CONSISTENT;
-}
-
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);
- clear_consistency_attr(q, req->memory, &req->flags);
- return ret ? ret : vb2_core_reqbufs(q, req->memory,
- req->flags, &req->count);
+ return ret ? ret : vb2_core_reqbufs(q, req->memory, &req->count);
}
EXPORT_SYMBOL_GPL(vb2_reqbufs);

@@ -769,7 +759,6 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
unsigned i;

fill_buf_caps(q, &create->capabilities);
- clear_consistency_attr(q, create->memory, &create->flags);
create->index = q->num_buffers;
if (create->count == 0)
return ret != -EBUSY ? ret : 0;
@@ -813,7 +802,6 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
if (requested_sizes[i] == 0)
return -EINVAL;
return ret ? ret : vb2_core_create_bufs(q, create->memory,
- create->flags,
&create->count,
requested_planes,
requested_sizes);
@@ -998,12 +986,11 @@ int vb2_ioctl_reqbufs(struct file *file, void *priv,
int res = vb2_verify_memory_type(vdev->queue, p->memory, p->type);

fill_buf_caps(vdev->queue, &p->capabilities);
- clear_consistency_attr(vdev->queue, p->memory, &p->flags);
if (res)
return res;
if (vb2_queue_is_busy(vdev, file))
return -EBUSY;
- res = vb2_core_reqbufs(vdev->queue, p->memory, p->flags, &p->count);
+ res = vb2_core_reqbufs(vdev->queue, p->memory, &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)
@@ -1021,7 +1008,6 @@ int vb2_ioctl_create_bufs(struct file *file, void *priv,

p->index = vdev->queue->num_buffers;
fill_buf_caps(vdev->queue, &p->capabilities);
- clear_consistency_attr(vdev->queue, p->memory, &p->flags);
/*
* If count == 0, then just check if memory and type are valid.
* Any -EBUSY result from vb2_verify_memory_type can be mapped to 0.
diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
index 593bcf6c373502..a99e82ec9ab60d 100644
--- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
+++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
@@ -246,9 +246,6 @@ struct v4l2_format32 {
* @memory: buffer memory type
* @format: frame format, for which buffers are requested
* @capabilities: capabilities of this buffer type.
- * @flags: additional buffer management attributes (ignored unless the
- * queue has V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS capability and
- * configured for MMAP streaming I/O).
* @reserved: future extensions
*/
struct v4l2_create_buffers32 {
@@ -257,8 +254,7 @@ struct v4l2_create_buffers32 {
__u32 memory; /* enum v4l2_memory */
struct v4l2_format32 format;
__u32 capabilities;
- __u32 flags;
- __u32 reserved[6];
+ __u32 reserved[7];
};

static int __bufsize_v4l2_format(struct v4l2_format32 __user *p32, u32 *size)
@@ -359,8 +355,7 @@ static int get_v4l2_create32(struct v4l2_create_buffers __user *p64,
{
if (!access_ok(p32, sizeof(*p32)) ||
copy_in_user(p64, p32,
- offsetof(struct v4l2_create_buffers32, format)) ||
- assign_in_user(&p64->flags, &p32->flags))
+ offsetof(struct v4l2_create_buffers32, format)))
return -EFAULT;
return __get_v4l2_format32(&p64->format, &p32->format,
aux_buf, aux_space);
@@ -422,7 +417,6 @@ static int put_v4l2_create32(struct v4l2_create_buffers __user *p64,
copy_in_user(p32, p64,
offsetof(struct v4l2_create_buffers32, format)) ||
assign_in_user(&p32->capabilities, &p64->capabilities) ||
- assign_in_user(&p32->flags, &p64->flags) ||
copy_in_user(p32->reserved, p64->reserved, sizeof(p64->reserved)))
return -EFAULT;
return __put_v4l2_format32(&p64->format, &p32->format);
diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
index 2a22e13a630346..e0520c85a3b725 100644
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -2042,6 +2042,9 @@ 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);
}

@@ -2081,7 +2084,7 @@ static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
if (ret)
return ret;

- CLEAR_AFTER_FIELD(create, flags);
+ CLEAR_AFTER_FIELD(create, capabilities);

v4l_sanitize_format(&create->format);

diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index 52ef92049073e3..bbb3f26fbde978 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -744,8 +744,6 @@ 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.
- * @flags: auxiliary queue/buffer management flags. Currently, the only
- * used flag is %V4L2_FLAG_MEMORY_NON_CONSISTENT.
* @count: requested buffer count.
*
* Videobuf2 core helper to implement VIDIOC_REQBUF() operation. It is called
@@ -770,13 +768,12 @@ 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 flags, unsigned int *count);
+ 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.
- * @flags: auxiliary queue/buffer management flags.
* @count: requested buffer count.
* @requested_planes: number of planes requested.
* @requested_sizes: array with the size of the planes.
@@ -794,7 +791,7 @@ 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 flags, unsigned int *count,
+ unsigned int *count,
unsigned int requested_planes,
const unsigned int requested_sizes[]);

diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index c7b70ff53bc1dd..235db7754606d6 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -191,8 +191,6 @@ 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 {
/*
@@ -949,10 +947,7 @@ struct v4l2_requestbuffers {
__u32 type; /* enum v4l2_buf_type */
__u32 memory; /* enum v4l2_memory */
__u32 capabilities;
- union {
- __u32 flags;
- __u32 reserved[1];
- };
+ __u32 reserved[1];
};

/* capabilities for struct v4l2_requestbuffers and v4l2_create_buffers */
@@ -2456,9 +2451,6 @@ struct v4l2_dbg_chip_info {
* @memory: enum v4l2_memory; buffer memory type
* @format: frame format, for which buffers are requested
* @capabilities: capabilities of this buffer type.
- * @flags: additional buffer management attributes (ignored unless the
- * queue has V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS capability
- * and configured for MMAP streaming I/O).
* @reserved: future extensions
*/
struct v4l2_create_buffers {
@@ -2467,8 +2459,7 @@ struct v4l2_create_buffers {
__u32 memory;
struct v4l2_format format;
__u32 capabilities;
- __u32 flags;
- __u32 reserved[6];
+ __u32 reserved[7];
};

/*
--
2.28.0