media: v4l2: Add REMOVE_BUFS ioctl

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 <[e-mail]>
Reviewed-by: Mauro Carvalho Chehab <[e-mail]>
Signed-off-by: Hans Verkuil <[e-mail]>
[hverkuil: vidioc-remove-bufs.rst: mention no bufs are freed on error]

Documentation/userspace-api/media/v4l/user-func.rst

···
     vidioc-query-dv-timings
     vidioc-querystd
     vidioc-reqbufs
+    vidioc-remove-bufs
     vidioc-s-hw-freq-seek
     vidioc-streamon
     vidioc-subdev-enum-frame-interval

Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst

···
+.. 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. If an error occurs, no
+buffers will be freed and one of the error codes below will be returned:
+
+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.

Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst

···
 .. _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
 

drivers/media/common/videobuf2/videobuf2-core.c

···
 }
 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

drivers/media/common/videobuf2/videobuf2-v4l2.c

···
 		*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)
···
  */
 
 /* 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)

drivers/media/v4l2-core/v4l2-dev.c

···
 		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) {

drivers/media/v4l2-core/v4l2-ioctl.c

···
 	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;
···
 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);
 
···
 		return ret;
 
 	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);
 }
···
 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);
 
···
 	memset_after(create, 0, flags);
 
 	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);
 
···
 	int ret = check_fmt(file, b->type);
 
 	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,
···
 	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)
 

include/media/v4l2-ioctl.h

···
  *	: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
···
 				  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,

include/media/videobuf2-core.h

···
 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
  *
  * @q:		pointer to &struct vb2_queue with videobuf2 queue.

include/media/videobuf2-v4l2.h

···
 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 */
 

include/uapi/linux/videodev2.h

···
 #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
···
 	__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
  *
···
 #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! */