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From: Benjamin Gaignard <benjamin.gaignard@collabora.com>
To: hverkuil@xs4all.nl,
	mchehab@kernel.org
Cc: linux-kernel@vger.kernel.org,
	linux-media@vger.kernel.org,
	kernel@collabora.com,
	Benjamin Gaignard <benjamin.gaignard@collabora.com>
Subject: [PATCH v16 6/8] media: v4l2: Add DELETE_BUFS ioctl
Date: Fri, 15 Dec 2023 10:08:11 +0100
Message-Id: <20231215090813.15610-7-benjamin.gaignard@collabora.com>
In-Reply-To: <20231215090813.15610-1-benjamin.gaignard@collabora.com>
References: <20231215090813.15610-1-benjamin.gaignard@collabora.com>
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VIDIOC_DELETE_BUFS ioctl allows to delete buffers from a queue.
The number of buffers to delete in given by count field of
struct v4l2_delete_buffers and the range start at the index
specified in the same structure.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
---
version 16:
- Take care of 'min_queued_buffers' when deleting buffers
- Add more check about buffers range limit when deleting buffers.

 .../userspace-api/media/v4l/user-func.rst     |  1 +
 .../media/v4l/vidioc-delete-bufs.rst          | 79 +++++++++++++++++++
 .../media/v4l/vidioc-reqbufs.rst              |  1 +
 .../media/common/videobuf2/videobuf2-core.c   | 42 ++++++++++
 .../media/common/videobuf2/videobuf2-v4l2.c   | 20 +++++
 drivers/media/v4l2-core/v4l2-dev.c            |  1 +
 drivers/media/v4l2-core/v4l2-ioctl.c          | 19 +++++
 include/media/v4l2-ioctl.h                    |  4 +
 include/media/videobuf2-core.h                | 12 +++
 include/media/videobuf2-v4l2.h                | 13 +++
 include/uapi/linux/videodev2.h                | 17 ++++
 11 files changed, 209 insertions(+)
 create mode 100644 Documentation/userspace-api/media/v4l/vidioc-delete-bufs.rst

diff --git a/Documentation/userspace-api/media/v4l/user-func.rst b/Documentation/userspace-api/media/v4l/user-func.rst
index 15ff0bf7bbe6..3fd567695477 100644
--- a/Documentation/userspace-api/media/v4l/user-func.rst
+++ b/Documentation/userspace-api/media/v4l/user-func.rst
@@ -17,6 +17,7 @@ Function Reference
     vidioc-dbg-g-chip-info
     vidioc-dbg-g-register
     vidioc-decoder-cmd
+    vidioc-delete-bufs
     vidioc-dqevent
     vidioc-dv-timings-cap
     vidioc-encoder-cmd
diff --git a/Documentation/userspace-api/media/v4l/vidioc-delete-bufs.rst b/Documentation/userspace-api/media/v4l/vidioc-delete-bufs.rst
new file mode 100644
index 000000000000..5d5326b063c0
--- /dev/null
+++ b/Documentation/userspace-api/media/v4l/vidioc-delete-bufs.rst
@@ -0,0 +1,79 @@
+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+.. c:namespace:: V4L
+
+.. _VIDIOC_DELETE_BUFS:
+
+************************
+ioctl VIDIOC_DELETE_BUFS
+************************
+
+Name
+====
+
+VIDIOC_DELETE_BUFS - Deletes buffers from a queue
+Drivers using this feature must expose the ``V4L2_BUF_CAP_SUPPORTS_DELETE_BUFS``
+capability on the queue :c:func:`VIDIOC_REQBUFS` or :c:func:`VIDIOC_CREATE_BUFS`
+are invoked.
+
+Synopsis
+========
+
+.. c:macro:: VIDIOC_DELETE_BUFs
+
+``int ioctl(int fd, VIDIOC_DELETE_BUFs, struct v4l2_delete_buffers *argp)``
+
+Arguments
+=========
+
+``fd``
+    File descriptor returned by :c:func:`open()`.
+
+``argp``
+    Pointer to struct :c:type:`v4l2_delete_buffers`.
+
+Description
+===========
+
+Applications can optionally call the :ref:`VIDIOC_DELETE_BUFS` ioctl to
+delete buffers from a queue.
+
+.. c:type:: v4l2_delete_buffers
+
+.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
+
+.. flat-table:: struct v4l2_delete_buffers
+    :header-rows:  0
+    :stub-columns: 0
+    :widths:       1 1 2
+
+    * - __u32
+      - ``index``
+      - The starting buffer index to delete.
+    * - __u32
+      - ``count``
+      - The number of buffers to be deleted with indices 'index' until 'index + count - 1'.
+        All buffers in this range must be valid and in DEQUEUED state.
+        In error case errno is set to ``EINVAL`` error code.
+        If count is set to 0 :ref:`VIDIOC_DELETE_BUFS` will 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.
+
+EINVAL
+    The buffer ``index`` doesn't exist in the queue.
diff --git a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
index 0b3a41a45d05..14d4a49c2945 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-DELETE-BUFS:
 
 .. raw:: latex
 
diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index 67ce823a0196..3b32791e70a8 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -1674,6 +1674,48 @@ 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_delete_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 + count > q->max_num_buffers)
+		return -EINVAL;
+
+	/* If streaming keep at least min_queued_buffers + 1 buffers */
+	if (q->streaming && (q_num_bufs - count < q->min_queued_buffers + 1))
+		return -EINVAL;
+
+	mutex_lock(&q->mmap_lock);
+
+	/* Check that all buffers in the range exist */
+	for (i = start; i < start + count && i < q->max_num_buffers; i++) {
+		struct vb2_buffer *vb = vb2_get_buffer(q, i);
+
+		if (!vb) {
+			ret = -EINVAL;
+			goto unlock;
+		}
+		if (vb->state != VB2_BUF_STATE_DEQUEUED) {
+			ret = -EINVAL;
+			goto unlock;
+		}
+	}
+	__vb2_queue_free(q, start, count);
+	dprintk(q, 2, "buffers deleted\n");
+
+unlock:
+	mutex_unlock(&q->mmap_lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(vb2_core_delete_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 3c0c423c5674..729641e004d2 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -686,6 +686,8 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
 		*caps |= V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS;
 	if (q->supports_requests)
 		*caps |= V4L2_BUF_CAP_SUPPORTS_REQUESTS;
+	if (q->supports_delete_bufs)
+		*caps |= V4L2_BUF_CAP_SUPPORTS_DELETE_BUFS;
 }
 
 static void validate_memory_flags(struct vb2_queue *q,
@@ -743,6 +745,12 @@ int vb2_prepare_buf(struct vb2_queue *q, struct media_device *mdev,
 }
 EXPORT_SYMBOL_GPL(vb2_prepare_buf);
 
+int vb2_delete_bufs(struct vb2_queue *q, struct v4l2_delete_buffers *d)
+{
+	return vb2_core_delete_bufs(q, d->index, d->count);
+}
+EXPORT_SYMBOL_GPL(vb2_delete_bufs);
+
 int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
 {
 	unsigned requested_planes = 1;
@@ -1004,6 +1012,18 @@ EXPORT_SYMBOL_GPL(vb2_poll);
 
 /* vb2 ioctl helpers */
 
+int vb2_ioctl_delete_bufs(struct file *file, void *priv,
+			  struct v4l2_delete_buffers *p)
+{
+	struct video_device *vdev = video_devdata(file);
+
+	if (vb2_queue_is_busy(vdev->queue, file))
+		return -EBUSY;
+
+	return vb2_delete_bufs(vdev->queue, p);
+}
+EXPORT_SYMBOL_GPL(vb2_ioctl_delete_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..e764af2e29ff 100644
--- a/drivers/media/v4l2-core/v4l2-dev.c
+++ b/drivers/media/v4l2-core/v4l2-dev.c
@@ -722,6 +722,7 @@ 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);
+		SET_VALID_IOCTL(ops, VIDIOC_DELETE_BUFS, vidioc_delete_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 33076af4dfdb..19af075cee6b 100644
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -489,6 +489,13 @@ static void v4l_print_create_buffers(const void *arg, bool write_only)
 	v4l_print_format(&p->format, write_only);
 }
 
+static void v4l_print_delete_buffers(const void *arg, bool write_only)
+{
+	const struct v4l2_delete_buffers *p = arg;
+
+	pr_cont("index=%u, count=%u\n", p->index, p->count);
+}
+
 static void v4l_print_streamparm(const void *arg, bool write_only)
 {
 	const struct v4l2_streamparm *p = arg;
@@ -2161,6 +2168,17 @@ static int v4l_prepare_buf(const struct v4l2_ioctl_ops *ops,
 	return ret ? ret : ops->vidioc_prepare_buf(file, fh, b);
 }
 
+static int v4l_delete_bufs(const struct v4l2_ioctl_ops *ops,
+			   struct file *file, void *fh, void *arg)
+{
+	struct v4l2_delete_buffers *delete = arg;
+	int ret = check_fmt(file, delete->type);
+
+	memset_after(delete, 0, type);
+
+	return ret ? ret : ops->vidioc_delete_bufs(file, fh, delete);
+}
+
 static int v4l_g_parm(const struct v4l2_ioctl_ops *ops,
 				struct file *file, void *fh, void *arg)
 {
@@ -2910,6 +2928,7 @@ 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_DELETE_BUFS, v4l_delete_bufs, v4l_print_delete_buffers, INFO_FL_PRIO | INFO_FL_QUEUE | INFO_FL_CLEAR(v4l2_delete_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..55afbde54211 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_delete_bufs: pointer to the function that implements
+ *	:ref:`VIDIOC_DELETE_BUFS <vidioc_delete_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_delete_bufs)(struct file *file, void *fh,
+				  struct v4l2_delete_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 e4c1fc7ae82f..7abdee874698 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -507,6 +507,7 @@ struct vb2_buf_ops {
  * @supports_requests: this queue supports the Request API.
  * @requires_requests: this queue requires the Request API. If this is set to 1,
  *		then supports_requests must be set to 1 as well.
+ * @supports_delete_bufs: this queue supports DELETE_BUFS ioctl.
  * @uses_qbuf:	qbuf was used directly for this queue. Set to 1 the first
  *		time this is called. Set to 0 when the queue is canceled.
  *		If this is 1, then you cannot queue buffers from a request.
@@ -612,6 +613,7 @@ struct vb2_queue {
 	unsigned int		   quirk_poll_must_check_waiting_for_buffers:1;
 	unsigned int			supports_requests:1;
 	unsigned int			requires_requests:1;
+	unsigned int			supports_delete_bufs:1;
 	unsigned int			uses_qbuf:1;
 	unsigned int			uses_requests:1;
 	unsigned int			allow_cache_hints:1;
@@ -864,6 +866,16 @@ 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_delete_bufs() -
+ * @q:		pointer to &struct vb2_queue with videobuf2 queue.
+ * @start:	first index of the range of buffers to delete.
+ * @count:	number of buffers to delete.
+ *
+ *  Return: returns zero on success; an error code otherwise.
+ */
+int vb2_core_delete_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..79cea8459f52 100644
--- a/include/media/videobuf2-v4l2.h
+++ b/include/media/videobuf2-v4l2.h
@@ -118,6 +118,17 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create);
  */
 int vb2_prepare_buf(struct vb2_queue *q, struct media_device *mdev,
 		    struct v4l2_buffer *b);
+/**
+ * vb2_delete_bufs() - Delete buffers from the queue
+ *
+ * @q:		pointer to &struct vb2_queue with videobuf2 queue.
+ * @d:		delete parameter, passed from userspace to
+ *		&v4l2_ioctl_ops->vidioc_delete_bufs handler in driver
+ *
+ * The return values from this function are intended to be directly returned
+ * from &v4l2_ioctl_ops->vidioc_delete_bufs handler in driver.
+ */
+int vb2_delete_bufs(struct vb2_queue *q, struct v4l2_delete_buffers *d);
 
 /**
  * vb2_qbuf() - Queue a buffer from userspace
@@ -334,6 +345,8 @@ 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_delete_bufs(struct file *file, void *priv,
+			  struct v4l2_delete_buffers *p);
 
 /* struct v4l2_file_operations helpers */
 
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index 68e7ac178cc2..ce436f924782 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_DELETE_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_delete_buffers - VIDIOC_DELETE_BUFS argument
+ * @index:	the first buffer to be deleted
+ * @count:	number of buffers to delete
+ * @type:	enum v4l2_buf_type
+ * @reserved:	future extensions
+ */
+struct v4l2_delete_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_DELETE_BUFS	_IOWR('V', 104, struct v4l2_delete_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