Re: [PATCH v8 13/53] media: Report the maximum possible number of buffers for the queue

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Le 02/10/2023 à 15:37, Hans Verkuil a écrit :
On 27/09/2023 17:35, Benjamin Gaignard wrote:
Use one of the struct v4l2_create_buffers reserved bytes to report
the maximum possible number of buffers for the queue.
V4l2 framework set V4L2_BUF_CAP_SUPPORTS_SET_MAX_BUFS flags in queue
capabilities so userland can know when the field is valid.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
---
  .../userspace-api/media/v4l/vidioc-create-bufs.rst       | 8 ++++++--
  Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst | 1 +
  drivers/media/common/videobuf2/videobuf2-v4l2.c          | 9 +++++++--
  drivers/media/v4l2-core/v4l2-ioctl.c                     | 4 ++--
  include/uapi/linux/videodev2.h                           | 7 ++++++-
  5 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst b/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst
index a048a9f6b7b6..1a46549e7462 100644
--- a/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst
@@ -116,9 +116,13 @@ than the number requested.
        - ``flags``
        - Specifies additional buffer management attributes.
  	See :ref:`memory-flags`.
-
      * - __u32
-      - ``reserved``\ [6]
+      - ``max_buffers``
+      - If V4L2_BUF_CAP_SUPPORTS_SET_MAX_BUFS capability flag is set
+        this field indicate the maximum possible number of buffers
+        for this queue.
+    * - __u32
+      - ``reserved``\ [5]
        - 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 099fa6695167..0395187e1a5a 100644
--- a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
@@ -120,6 +120,7 @@ aborting or finishing any DMA in progress, an implicit
  .. _V4L2-BUF-CAP-SUPPORTS-ORPHANED-BUFS:
  .. _V4L2-BUF-CAP-SUPPORTS-M2M-HOLD-CAPTURE-BUF:
  .. _V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS:
+.. _V4L2-BUF-CAP-SUPPORTS-SET-MAX-BUFS:
.. raw:: latex diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index 278ea1107b01..655133f1ae2b 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -686,6 +686,7 @@ EXPORT_SYMBOL(vb2_querybuf);
  static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
  {
  	*caps = V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
+	*caps |= V4L2_BUF_CAP_SUPPORTS_SET_MAX_BUFS;
  	if (q->io_modes & VB2_MMAP)
  		*caps |= V4L2_BUF_CAP_SUPPORTS_MMAP;
  	if (q->io_modes & VB2_USERPTR)
@@ -767,9 +768,13 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
fill_buf_caps(q, &create->capabilities);
  	validate_memory_flags(q, create->memory, &create->flags);
-	create->index = q->num_buffers;
-	if (create->count == 0)
+
+	create->max_buffers = q->max_num_buffers;
+
+	if (create->count == 0) {
+		create->index = vb2_get_num_buffers(q);
This breaks git bisect: this function isn't introduced until patch 21/53.

Note: with the build scripts you can just run it with:

./build.sh -patches 53 ...

and it will apply each patch in sequence and attempt to compile it.

It should  be create->index = q->num_buffers;
The error is also in v9...


Regards,

	Hans

  		return ret != -EBUSY ? ret : 0;
+	}
switch (f->type) {
  	case V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE:
diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
index f4d9d6279094..700db197e371 100644
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -483,9 +483,9 @@ static void v4l_print_create_buffers(const void *arg, bool write_only)
  {
  	const struct v4l2_create_buffers *p = arg;
- pr_cont("index=%d, count=%d, memory=%s, capabilities=0x%08x, ",
+	pr_cont("index=%d, count=%d, memory=%s, capabilities=0x%08x, max buffers=%u",
  		p->index, p->count, prt_names(p->memory, v4l2_memory_names),
-		p->capabilities);
+		p->capabilities, p->max_buffers);
  	v4l_print_format(&p->format, write_only);
  }
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index 78260e5d9985..b0dbb1be728c 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -1034,6 +1034,7 @@ struct v4l2_requestbuffers {
  #define V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS		(1 << 4)
  #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_SET_MAX_BUFS		(1 << 7)
/**
   * struct v4l2_plane - plane info for multi-planar buffers
@@ -2604,6 +2605,9 @@ struct v4l2_dbg_chip_info {
   * @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).
+ * @max_buffers: if V4L2_BUF_CAP_SUPPORTS_SET_MAX_BUFS capability flag is set
+ *		 this field indicate the maximum possible number of buffers
+ *		 for this queue.
   * @reserved:	future extensions
   */
  struct v4l2_create_buffers {
@@ -2613,7 +2617,8 @@ struct v4l2_create_buffers {
  	struct v4l2_format	format;
  	__u32			capabilities;
  	__u32			flags;
-	__u32			reserved[6];
+	__u32			max_buffers;
+	__u32			reserved[5];
  };
/*




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