the maximum possible number of buffers for the queue.
V4l2 framework set V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS flags in queue
capabilities so userland can know when the field is valid.
Does the same change in v4l2_create_buffers32 structure.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
---
  .../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          | 2 ++
  drivers/media/v4l2-core/v4l2-compat-ioctl32.c            | 9 ++++++++-
  drivers/media/v4l2-core/v4l2-ioctl.c                     | 4 ++--
  include/uapi/linux/videodev2.h                           | 7 ++++++-
  6 files changed, 25 insertions(+), 6 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..49232c9006c2 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_num_buffers``
+      - If the V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS capability flag is set
+        this field indicates 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..0b3a41a45d05 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-MAX-NUM-BUFFERS:
  
  .. raw:: latex
  

diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index f3cf4b235c1f..bdfc3a253c65 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c

@@ -762,6 +762,8 @@ 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 = vb2_get_num_buffers(q);
+	create->max_num_buffers = q->max_num_buffers;
+	create->capabilities |= V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS;
  	if (create->count == 0)
  		return ret != -EBUSY ? ret : 0;
  

diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
index f3bed37859a2..5aac5cf780b3 100644
--- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
+++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c

@@ -116,6 +116,9 @@ struct v4l2_format32 {
   * @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_num_buffers: if V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS capability flag is set
+ *		this field indicate the maximum possible number of buffers
+ *		for this queue.
   * @reserved:	future extensions
   */
  struct v4l2_create_buffers32 {

@@ -125,7 +128,8 @@ struct v4l2_create_buffers32 {
  	struct v4l2_format32	format;
  	__u32			capabilities;
  	__u32			flags;
-	__u32			reserved[6];
+	__u32			max_num_buffers;
+	__u32			reserved[5];
  };
  
  static int get_v4l2_format32(struct v4l2_format *p64,

@@ -175,6 +179,8 @@ static int get_v4l2_create32(struct v4l2_create_buffers *p64,
  		return -EFAULT;
  	if (copy_from_user(&p64->flags, &p32->flags, sizeof(p32->flags)))
  		return -EFAULT;
+	if (copy_from_user(&p64->max_num_buffers, &p32->max_num_buffers, sizeof(p32->max_num_buffers)))
+		return -EFAULT;
  	return get_v4l2_format32(&p64->format, &p32->format);
  }
  

@@ -221,6 +227,7 @@ static int put_v4l2_create32(struct v4l2_create_buffers *p64,
  			 offsetof(struct v4l2_create_buffers32, format)) ||
  	    put_user(p64->capabilities, &p32->capabilities) ||
  	    put_user(p64->flags, &p32->flags) ||
+	    put_user(p64->max_num_buffers, &p32->max_num_buffers) ||
  	    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 9b1de54ce379..4d90424cbfc4 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 num buffers=%u",
  		p->index, p->count, prt_names(p->memory, v4l2_memory_names),
-		p->capabilities);
+		p->capabilities, p->max_num_buffers);
  	v4l_print_format(&p->format, write_only);
  }
  

diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index c3d4e490ce7c..13ddb5abf584 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h

@@ -1035,6 +1035,7 @@ 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_MAX_NUM_BUFFERS		(1 << 7)
  
  /**
   * struct v4l2_plane - plane info for multi-planar buffers

@@ -2605,6 +2606,9 @@ 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_num_buffers: if V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS capability flag is set
+ *		this field indicate the maximum possible number of buffers
+ *		for this queue.
   * @reserved:	future extensions
   */
  struct v4l2_create_buffers {

@@ -2614,7 +2618,8 @@ struct v4l2_create_buffers {
  	struct v4l2_format	format;
  	__u32			capabilities;
  	__u32			flags;
-	__u32			reserved[6];
+	__u32			max_num_buffers;
+	__u32			reserved[5];
  };
  
  /*