media: core: Report the maximum possible number of buffers for the queue

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_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>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

diff --git a/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst b/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst
index a048a9f..49232c9 100644 (file)
--- 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 099fa66..0b3a41a 100644 (file)
--- 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 3d71c20..440c3b1 100644 (file)
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -756,6 +756,8 @@ 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 f3bed37..8c07400 100644 (file)
--- 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 +179,9 @@ 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 +228,7 @@ 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 9b1de54..4d90424 100644 (file)
--- 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 c3d4e49..13ddb5a 100644 (file)
--- 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];
 };
 
 /*