[PATCH v21 7/9] media: v4l2: Add REMOVE_BUFS ioctl

From: Benjamin Gaignard
Date: Thu Mar 14 2024 - 11:34:37 EST

VIDIOC_REMOVE_BUFS ioctl allows to remove buffers from a queue.
The number of buffers to remove in given by count field of
struct v4l2_remove_buffers and the range start at the index
specified in the same structure.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
---
changes in version 21:
- Be more careful about checking remove_bufs type field vs queue type.
- Add documentation about type checking error.
- Always set capabilities flags field.

.../userspace-api/media/v4l/user-func.rst | 1 +
.../media/v4l/vidioc-remove-bufs.rst | 85 +++++++++++++++++++
.../media/v4l/vidioc-reqbufs.rst | 1 +
.../media/common/videobuf2/videobuf2-core.c | 38 +++++++++
.../media/common/videobuf2/videobuf2-v4l2.c | 20 ++++-
drivers/media/v4l2-core/v4l2-dev.c | 3 +
drivers/media/v4l2-core/v4l2-ioctl.c | 30 +++++++
include/media/v4l2-ioctl.h | 4 +
include/media/videobuf2-core.h | 10 +++
include/media/videobuf2-v4l2.h | 2 +
include/uapi/linux/videodev2.h | 17 ++++
11 files changed, 210 insertions(+), 1 deletion(-)
create mode 100644 Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst

diff --git a/Documentation/userspace-api/media/v4l/user-func.rst b/Documentation/userspace-api/media/v4l/user-func.rst
index 15ff0bf7bbe6..6f661138801c 100644
--- a/Documentation/userspace-api/media/v4l/user-func.rst
+++ b/Documentation/userspace-api/media/v4l/user-func.rst
@@ -62,6 +62,7 @@ Function Reference
vidioc-query-dv-timings
vidioc-querystd
vidioc-reqbufs
+ vidioc-remove-bufs
vidioc-s-hw-freq-seek
vidioc-streamon
vidioc-subdev-enum-frame-interval
diff --git a/Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst b/Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst
new file mode 100644
index 000000000000..0cbc8c7313b7
--- /dev/null
+++ b/Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst
@@ -0,0 +1,85 @@
+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+.. c:namespace:: V4L
+
+.. _VIDIOC_REMOVE_BUFS:
+
+************************
+ioctl VIDIOC_REMOVE_BUFS
+************************
+
+Name
+====
+
+VIDIOC_REMOVE_BUFS - Removes buffers from a queue
+
+Synopsis
+========
+
+.. c:macro:: VIDIOC_REMOVE_BUFS
+
+``int ioctl(int fd, VIDIOC_REMOVE_BUFS, struct v4l2_remove_buffers *argp)``
+
+Arguments
+=========
+
+``fd``
+ File descriptor returned by :c:func:`open()`.
+
+``argp``
+ Pointer to struct :c:type:`v4l2_remove_buffers`.
+
+Description
+===========
+
+Applications can optionally call the :ref:`VIDIOC_REMOVE_BUFS` ioctl to
+remove buffers from a queue.
+:ref:`VIDIOC_CREATE_BUFS` ioctl support is mandatory to enable :ref:`VIDIOC_REMOVE_BUFS`.
+This ioctl is available if the ``V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS`` capability
+is set on the queue when :c:func:`VIDIOC_REQBUFS` or :c:func:`VIDIOC_CREATE_BUFS`
+are invoked.
+
+.. c:type:: v4l2_remove_buffers
+
+.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
+
+.. flat-table:: struct v4l2_remove_buffers
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 1 1 2
+
+ * - __u32
+ - ``index``
+ - The starting buffer index to remove. This field is ignored if count == 0.
+ * - __u32
+ - ``count``
+ - The number of buffers to be removed with indices 'index' until 'index + count - 1'.
+ All buffers in this range must be valid and in DEQUEUED state.
+ :ref:`VIDIOC_REMOVE_BUFS` will always check the validity of ``type`, if it is
+ invalid it returns ``EINVAL`` error code.
+ If count is set to 0 :ref:`VIDIOC_REMOVE_BUFS` will do nothing and return 0.
+ * - __u32
+ - ``type``
+ - Type of the stream or buffers, this is the same as the struct
+ :c:type:`v4l2_format` ``type`` field. See
+ :c:type:`v4l2_buf_type` for valid values.
+ * - __u32
+ - ``reserved``\ [13]
+ - A place holder for future extensions. Drivers and applications
+ must set the array to zero.
+
+Return Value
+============
+
+On success 0 is returned, on error -1 and the ``errno`` variable is set
+appropriately. The generic error codes are described at the
+:ref:`Generic Error Codes <gen-errors>` chapter.
+
+EBUSY
+ File I/O is in progress.
+ One or more of the buffers in the range ``index`` to ``index + count - 1`` are not
+ in DEQUEUED state.
+
+EINVAL
+ One or more of the buffers in the range ``index`` to ``index + count - 1`` do not
+ exist in the queue.
+ The buffer type (``type`` field) is not valid.
diff --git a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
index 0b3a41a45d05..bbc22dd76032 100644
--- a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
@@ -121,6 +121,7 @@ aborting or finishing any DMA in progress, an implicit
.. _V4L2-BUF-CAP-SUPPORTS-M2M-HOLD-CAPTURE-BUF:
.. _V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS:
.. _V4L2-BUF-CAP-SUPPORTS-MAX-NUM-BUFFERS:
+.. _V4L2-BUF-CAP-SUPPORTS-REMOVE-BUFS:

.. raw:: latex

diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index 009cea95d662..0b2b48e1b2df 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -1691,6 +1691,44 @@ int vb2_core_prepare_buf(struct vb2_queue *q, struct vb2_buffer *vb, void *pb)
}
EXPORT_SYMBOL_GPL(vb2_core_prepare_buf);

+int vb2_core_remove_bufs(struct vb2_queue *q, unsigned int start, unsigned int count)
+{
+ unsigned int i, ret = 0;
+ unsigned int q_num_bufs = vb2_get_num_buffers(q);
+
+ if (count == 0)
+ return 0;
+
+ if (count > q_num_bufs)
+ return -EINVAL;
+
+ if (start > q->max_num_buffers - count)
+ return -EINVAL;
+
+ mutex_lock(&q->mmap_lock);
+
+ /* Check that all buffers in the range exist */
+ for (i = start; i < start + count; i++) {
+ struct vb2_buffer *vb = vb2_get_buffer(q, i);
+
+ if (!vb) {
+ ret = -EINVAL;
+ goto unlock;
+ }
+ if (vb->state != VB2_BUF_STATE_DEQUEUED) {
+ ret = -EBUSY;
+ goto unlock;
+ }
+ }
+ __vb2_queue_free(q, start, count);
+ dprintk(q, 2, "%u buffers removed\n", count);
+
+unlock:
+ mutex_unlock(&q->mmap_lock);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(vb2_core_remove_bufs);
+
/*
* vb2_start_streaming() - Attempt to start streaming.
* @q: videobuf2 queue
diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index 03e8080a68a8..293f3d5f1c4e 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -685,7 +685,7 @@ static void vb2_set_flags_and_caps(struct vb2_queue *q, u32 memory,
*flags &= V4L2_MEMORY_FLAG_NON_COHERENT;
}

- *caps = V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
+ *caps |= V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
if (q->io_modes & VB2_MMAP)
*caps |= V4L2_BUF_CAP_SUPPORTS_MMAP;
if (q->io_modes & VB2_USERPTR)
@@ -1001,6 +1001,24 @@ EXPORT_SYMBOL_GPL(vb2_poll);

/* vb2 ioctl helpers */

+int vb2_ioctl_remove_bufs(struct file *file, void *priv,
+ struct v4l2_remove_buffers *d)
+{
+ struct video_device *vdev = video_devdata(file);
+
+ if (vdev->queue->type != d->type)
+ return -EINVAL;
+
+ if (d->count == 0)
+ return 0;
+
+ if (vb2_queue_is_busy(vdev->queue, file))
+ return -EBUSY;
+
+ return vb2_core_remove_bufs(vdev->queue, d->index, d->count);
+}
+EXPORT_SYMBOL_GPL(vb2_ioctl_remove_bufs);
+
int vb2_ioctl_reqbufs(struct file *file, void *priv,
struct v4l2_requestbuffers *p)
{
diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
index d13954bd31fd..e39e9742fdb5 100644
--- a/drivers/media/v4l2-core/v4l2-dev.c
+++ b/drivers/media/v4l2-core/v4l2-dev.c
@@ -722,6 +722,9 @@ static void determine_valid_ioctls(struct video_device *vdev)
SET_VALID_IOCTL(ops, VIDIOC_PREPARE_BUF, vidioc_prepare_buf);
SET_VALID_IOCTL(ops, VIDIOC_STREAMON, vidioc_streamon);
SET_VALID_IOCTL(ops, VIDIOC_STREAMOFF, vidioc_streamoff);
+ /* VIDIOC_CREATE_BUFS support is mandatory to enable VIDIOC_REMOVE_BUFS */
+ if (ops->vidioc_create_bufs)
+ SET_VALID_IOCTL(ops, VIDIOC_REMOVE_BUFS, vidioc_remove_bufs);
}

if (is_vid || is_vbi || is_meta) {
diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
index 6e7b8b682d13..5aeff5519407 100644
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -489,6 +489,14 @@ static void v4l_print_create_buffers(const void *arg, bool write_only)
v4l_print_format(&p->format, write_only);
}

+static void v4l_print_remove_buffers(const void *arg, bool write_only)
+{
+ const struct v4l2_remove_buffers *p = arg;
+
+ pr_cont("type=%s, index=%u, count=%u\n",
+ prt_names(p->type, v4l2_type_names), p->index, p->count);
+}
+
static void v4l_print_streamparm(const void *arg, bool write_only)
{
const struct v4l2_streamparm *p = arg;
@@ -2092,6 +2100,7 @@ static int v4l_overlay(const struct v4l2_ioctl_ops *ops,
static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,
struct file *file, void *fh, void *arg)
{
+ struct video_device *vfd = video_devdata(file);
struct v4l2_requestbuffers *p = arg;
int ret = check_fmt(file, p->type);

@@ -2100,6 +2109,10 @@ static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,

memset_after(p, 0, flags);

+ p->capabilities = 0;
+ if (is_valid_ioctl(vfd, VIDIOC_REMOVE_BUFS))
+ p->capabilities = V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS;
+
return ops->vidioc_reqbufs(file, fh, p);
}

@@ -2133,6 +2146,7 @@ static int v4l_dqbuf(const struct v4l2_ioctl_ops *ops,
static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
struct file *file, void *fh, void *arg)
{
+ struct video_device *vfd = video_devdata(file);
struct v4l2_create_buffers *create = arg;
int ret = check_fmt(file, create->format.type);

@@ -2143,6 +2157,10 @@ static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,

v4l_sanitize_format(&create->format);

+ create->capabilities = 0;
+ if (is_valid_ioctl(vfd, VIDIOC_REMOVE_BUFS))
+ create->capabilities = V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS;
+
ret = ops->vidioc_create_bufs(file, fh, create);

if (create->format.type == V4L2_BUF_TYPE_VIDEO_CAPTURE ||
@@ -2161,6 +2179,17 @@ static int v4l_prepare_buf(const struct v4l2_ioctl_ops *ops,
return ret ? ret : ops->vidioc_prepare_buf(file, fh, b);
}

+static int v4l_remove_bufs(const struct v4l2_ioctl_ops *ops,
+ struct file *file, void *fh, void *arg)
+{
+ struct v4l2_remove_buffers *remove = arg;
+
+ if (ops->vidioc_remove_bufs)
+ return ops->vidioc_remove_bufs(file, fh, remove);
+
+ return -ENOTTY;
+}
+
static int v4l_g_parm(const struct v4l2_ioctl_ops *ops,
struct file *file, void *fh, void *arg)
{
@@ -2910,6 +2939,7 @@ static const struct v4l2_ioctl_info v4l2_ioctls[] = {
IOCTL_INFO(VIDIOC_ENUM_FREQ_BANDS, v4l_enum_freq_bands, v4l_print_freq_band, 0),
IOCTL_INFO(VIDIOC_DBG_G_CHIP_INFO, v4l_dbg_g_chip_info, v4l_print_dbg_chip_info, INFO_FL_CLEAR(v4l2_dbg_chip_info, match)),
IOCTL_INFO(VIDIOC_QUERY_EXT_CTRL, v4l_query_ext_ctrl, v4l_print_query_ext_ctrl, INFO_FL_CTRL | INFO_FL_CLEAR(v4l2_query_ext_ctrl, id)),
+ IOCTL_INFO(VIDIOC_REMOVE_BUFS, v4l_remove_bufs, v4l_print_remove_buffers, INFO_FL_PRIO | INFO_FL_QUEUE | INFO_FL_CLEAR(v4l2_remove_buffers, type)),
};
#define V4L2_IOCTLS ARRAY_SIZE(v4l2_ioctls)

diff --git a/include/media/v4l2-ioctl.h b/include/media/v4l2-ioctl.h
index edb733f21604..bdbb7e542321 100644
--- a/include/media/v4l2-ioctl.h
+++ b/include/media/v4l2-ioctl.h
@@ -163,6 +163,8 @@ struct v4l2_fh;
* :ref:`VIDIOC_CREATE_BUFS <vidioc_create_bufs>` ioctl
* @vidioc_prepare_buf: pointer to the function that implements
* :ref:`VIDIOC_PREPARE_BUF <vidioc_prepare_buf>` ioctl
+ * @vidioc_remove_bufs: pointer to the function that implements
+ * :ref:`VIDIOC_REMOVE_BUFS <vidioc_remove_bufs>` ioctl
* @vidioc_overlay: pointer to the function that implements
* :ref:`VIDIOC_OVERLAY <vidioc_overlay>` ioctl
* @vidioc_g_fbuf: pointer to the function that implements
@@ -422,6 +424,8 @@ struct v4l2_ioctl_ops {
struct v4l2_create_buffers *b);
int (*vidioc_prepare_buf)(struct file *file, void *fh,
struct v4l2_buffer *b);
+ int (*vidioc_remove_bufs)(struct file *file, void *fh,
+ struct v4l2_remove_buffers *d);

int (*vidioc_overlay)(struct file *file, void *fh, unsigned int i);
int (*vidioc_g_fbuf)(struct file *file, void *fh,
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index b9333e2c7797..955237ac503d 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -870,6 +870,16 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
*/
int vb2_core_prepare_buf(struct vb2_queue *q, struct vb2_buffer *vb, void *pb);

+/**
+ * vb2_core_remove_bufs() -
+ * @q: pointer to &struct vb2_queue with videobuf2 queue.
+ * @start: first index of the range of buffers to remove.
+ * @count: number of buffers to remove.
+ *
+ * Return: returns zero on success; an error code otherwise.
+ */
+int vb2_core_remove_bufs(struct vb2_queue *q, unsigned int start, unsigned int count);
+
/**
* vb2_core_qbuf() - Queue a buffer from userspace
*
diff --git a/include/media/videobuf2-v4l2.h b/include/media/videobuf2-v4l2.h
index 5a845887850b..77ce8238ab30 100644
--- a/include/media/videobuf2-v4l2.h
+++ b/include/media/videobuf2-v4l2.h
@@ -334,6 +334,8 @@ int vb2_ioctl_streamon(struct file *file, void *priv, enum v4l2_buf_type i);
int vb2_ioctl_streamoff(struct file *file, void *priv, enum v4l2_buf_type i);
int vb2_ioctl_expbuf(struct file *file, void *priv,
struct v4l2_exportbuffer *p);
+int vb2_ioctl_remove_bufs(struct file *file, void *priv,
+ struct v4l2_remove_buffers *p);

/* struct v4l2_file_operations helpers */

diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index a8015e5e7fa4..2663213b76a4 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -1036,6 +1036,7 @@ struct v4l2_requestbuffers {
#define V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF (1 << 5)
#define V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS (1 << 6)
#define V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS (1 << 7)
+#define V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS (1 << 8)

/**
* struct v4l2_plane - plane info for multi-planar buffers
@@ -2624,6 +2625,20 @@ struct v4l2_create_buffers {
__u32 reserved[5];
};

+/**
+ * struct v4l2_remove_buffers - VIDIOC_REMOVE_BUFS argument
+ * @index: the first buffer to be removed
+ * @count: number of buffers to removed
+ * @type: enum v4l2_buf_type
+ * @reserved: future extensions
+ */
+struct v4l2_remove_buffers {
+ __u32 index;
+ __u32 count;
+ __u32 type;
+ __u32 reserved[13];
+};
+
/*
* I O C T L C O D E S F O R V I D E O D E V I C E S
*
@@ -2723,6 +2738,8 @@ struct v4l2_create_buffers {
#define VIDIOC_DBG_G_CHIP_INFO _IOWR('V', 102, struct v4l2_dbg_chip_info)

#define VIDIOC_QUERY_EXT_CTRL _IOWR('V', 103, struct v4l2_query_ext_ctrl)
+#define VIDIOC_REMOVE_BUFS _IOWR('V', 104, struct v4l2_remove_buffers)
+

/* Reminder: when adding new ioctls please add support for them to
drivers/media/v4l2-core/v4l2-compat-ioctl32.c as well! */
--
2.40.1