[PATCHv3 7/8] videobuf2: handle V4L2_MEMORY_FLAG_NON_COHERENT flag

Sergey Senozhatsky
2021-07-09T09:21:00Z

This patch lets user-space to request a non-coherent 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.

= CREATE_BUFS32

struct v4l2_create_buffers32 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 byte of a 4 byte ->reserved[1] member of struct
v4l2_requestbuffers. The struct, thus, now has reserved 3 bytes.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
.../media/v4l/vidioc-create-bufs.rst | 7 ++++-
.../media/v4l/vidioc-reqbufs.rst | 11 ++++---
.../media/common/videobuf2/videobuf2-core.c | 4 +--
.../media/common/videobuf2/videobuf2-v4l2.c | 31 +++++++++++++++++--
drivers/media/v4l2-core/v4l2-compat-ioctl32.c | 9 +++++-
drivers/media/v4l2-core/v4l2-ioctl.c | 4 +--
include/uapi/linux/videodev2.h | 9 ++++--
7 files changed, 60 insertions(+), 15 deletions(-)

diff --git a/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst b/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst
index f98f18c9e91c..a048a9f6b7b6 100644
--- a/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst
@@ -113,7 +113,12 @@ than the number requested.
``V4L2_MEMORY_MMAP`` and ``format.type`` to the buffer type.

* - __u32
- - ``reserved``\ [7]
+ - ``flags``
+ - Specifies additional buffer management attributes.
+ See :ref:`memory-flags`.
+
+ * - __u32
+ - ``reserved``\ [6]
- 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 e59306aba2b0..099fa6695167 100644
--- a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
@@ -104,10 +104,13 @@ 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
- - ``reserved``\ [1]
- - A place holder for future extensions. Drivers and applications
- must set the array to zero.
+ * - __u8
+ - ``flags``
+ - Specifies additional buffer management attributes.
+ See :ref:`memory-flags`.
+ * - __u8
+ - ``reserved``\ [3]
+ - Reserved for future extensions.

.. _v4l2-buf-capabilities:
.. _V4L2-BUF-CAP-SUPPORTS-MMAP:
diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index af4db310cf5e..38505783247e 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -762,7 +762,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
{
unsigned int num_buffers, allocated_buffers, num_planes = 0;
unsigned plane_sizes[VB2_MAX_PLANES] = { };
- bool coherent_mem = true;
+ bool coherent_mem = !(flags & V4L2_MEMORY_FLAG_NON_COHERENT);
unsigned int i;
int ret;

@@ -906,7 +906,7 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
{
unsigned int num_planes = 0, num_buffers, allocated_buffers;
unsigned plane_sizes[VB2_MAX_PLANES] = { };
- bool coherent_mem = true;
+ bool coherent_mem = !(flags & V4L2_MEMORY_FLAG_NON_COHERENT);
int ret;

if (q->num_buffers == VB2_MAX_FRAME) {
diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index b4f70ddb09b0..6edf4508c636 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -692,12 +692,32 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
#endif
}

+static void validate_memory_flags(struct vb2_queue *q,
+ int memory,
+ u32 *flags)
+{
+ if (!q->allow_cache_hints || memory != V4L2_MEMORY_MMAP) {
+ /*
+ * This needs to clear V4L2_MEMORY_FLAG_NON_COHERENT only,
+ * but in order to avoid bugs we zero out all bits.
+ */
+ *flags = 0;
+ } else {
+ /* Clear all unknown flags. */
+ *flags &= V4L2_MEMORY_FLAG_NON_COHERENT;
+ }
+}
+
int vb2_reqbufs(struct vb2_queue *q, struct v4l2_requestbuffers *req)
{
int ret = vb2_verify_memory_type(q, req->memory, req->type);
+ u32 flags = req->flags;

fill_buf_caps(q, &req->capabilities);
- return ret ? ret : vb2_core_reqbufs(q, req->memory, 0, &req->count);
+ validate_memory_flags(q, req->memory, &flags);
+ req->flags = flags;
+ return ret ? ret : vb2_core_reqbufs(q, req->memory,
+ req->flags, &req->count);
}
EXPORT_SYMBOL_GPL(vb2_reqbufs);

@@ -729,6 +749,7 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
unsigned i;

fill_buf_caps(q, &create->capabilities);
+ validate_memory_flags(q, create->memory, &create->flags);
create->index = q->num_buffers;
if (create->count == 0)
return ret != -EBUSY ? ret : 0;
@@ -772,7 +793,7 @@ 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,
- 0,
+ create->flags,
&create->count,
requested_planes,
requested_sizes);
@@ -969,13 +990,16 @@ 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);
+ u32 flags = p->flags;

fill_buf_caps(vdev->queue, &p->capabilities);
+ validate_memory_flags(vdev->queue, p->memory, &flags);
+ p->flags = flags;
if (res)
return res;
if (vb2_queue_is_busy(vdev, file))
return -EBUSY;
- res = vb2_core_reqbufs(vdev->queue, p->memory, 0, &p->count);
+ res = vb2_core_reqbufs(vdev->queue, p->memory, p->flags, &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)
@@ -993,6 +1017,7 @@ int vb2_ioctl_create_bufs(struct file *file, void *priv,

p->index = vdev->queue->num_buffers;
fill_buf_caps(vdev->queue, &p->capabilities);
+ validate_memory_flags(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 47aff3b19742..8176769a89fa 100644
--- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
+++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
@@ -126,6 +126,9 @@ 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 {
@@ -134,7 +137,8 @@ struct v4l2_create_buffers32 {
__u32 memory; /* enum v4l2_memory */
struct v4l2_format32 format;
__u32 capabilities;
- __u32 reserved[7];
+ __u32 flags;
+ __u32 reserved[6];
};

static int get_v4l2_format32(struct v4l2_format *p64,
@@ -182,6 +186,8 @@ static int get_v4l2_create32(struct v4l2_create_buffers *p64,
if (copy_from_user(p64, p32,
offsetof(struct v4l2_create_buffers32, format)))
return -EFAULT;
+ if (copy_from_user(&p64->flags, &p32->flags, sizeof(p32->flags)))
+ return -EFAULT;
return get_v4l2_format32(&p64->format, &p32->format);
}

@@ -227,6 +233,7 @@ static int put_v4l2_create32(struct v4l2_create_buffers *p64,
if (copy_to_user(p32, p64,
offsetof(struct v4l2_create_buffers32, format)) ||
put_user(p64->capabilities, &p32->capabilities) ||
+ put_user(p64->flags, &p32->flags) ||
copy_to_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 05d5db3d85e5..6a941da33998 100644
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -2004,7 +2004,7 @@ static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,
if (ret)
return ret;

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

return ops->vidioc_reqbufs(file, fh, p);
}
@@ -2045,7 +2045,7 @@ 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 9d11e1d9c934..7973aa0465d2 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -953,7 +953,8 @@ struct v4l2_requestbuffers {
__u32 type; /* enum v4l2_buf_type */
__u32 memory; /* enum v4l2_memory */
__u32 capabilities;
- __u32 reserved[1];
+ __u8 flags;
+ __u8 reserved[3];
};

#define V4L2_MEMORY_FLAG_NON_COHERENT (1 << 0)
@@ -2501,6 +2502,9 @@ 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 {
@@ -2509,7 +2513,8 @@ struct v4l2_create_buffers {
__u32 memory;
struct v4l2_format format;
__u32 capabilities;
- __u32 reserved[7];
+ __u32 flags;
+ __u32 reserved[6];
};

/*
--
2.32.0.93.g670b81a890-goog