Hello Thomasz,
Instead of adding another IOCTL to query the file-descriptor in user-space, why dont we extend the existing ones in v4l2/vb2?
When the memory type set is V4L2_MEMORY_DMABUF, call to VIDIOC_REQBUFS /VIDIOC_QUERYBUF from driver can take/return the fd. We will need to add another attribute to struct v4l2_requestbuffers for this.
struct v4l2_requestbuffers { ... __u32 buf_fd; };
The application requesting buffer would set it to -1, and will receive the fd's when it calls the vb2_querybuf. In the same way, application which is trying to attach to already allocated buffer will set this to valid fd when it calls vidioc_reqbuf, and in vb2_reqbuf depending on the memory type, this can be checked and used to attach with the dma_buf for the respective buffer.
Ofcourse, this requires changes in vb2_reqbufs and vb2_querybuf similar to what you did in vb2_expbufs.
Will there be any issues in such an approach?
Regards, Subash
On 01/23/2012 07:21 PM, Tomasz Stanislawski wrote:
This patch adds extension to V4L2 api. It allow to export a mmap buffer as file descriptor. New ioctl VIDIOC_EXPBUF is added. It takes a buffer offset used by mmap and return a file descriptor on success.
Signed-off-by: Tomasz Stanislawskit.stanislaws@samsung.com Signed-off-by: Kyungmin Parkkyungmin.park@samsung.com
drivers/media/video/v4l2-compat-ioctl32.c | 1 + drivers/media/video/v4l2-ioctl.c | 11 +++++++++++ include/linux/videodev2.h | 1 + include/media/v4l2-ioctl.h | 1 + 4 files changed, 14 insertions(+), 0 deletions(-)
diff --git a/drivers/media/video/v4l2-compat-ioctl32.c b/drivers/media/video/v4l2-compat-ioctl32.c index c68531b..0f18b5e 100644 --- a/drivers/media/video/v4l2-compat-ioctl32.c +++ b/drivers/media/video/v4l2-compat-ioctl32.c @@ -954,6 +954,7 @@ long v4l2_compat_ioctl32(struct file *file, unsigned int cmd, unsigned long arg) case VIDIOC_S_FBUF32: case VIDIOC_OVERLAY32: case VIDIOC_QBUF32:
- case VIDIOC_EXPBUF: case VIDIOC_DQBUF32: case VIDIOC_STREAMON32: case VIDIOC_STREAMOFF32:
diff --git a/drivers/media/video/v4l2-ioctl.c b/drivers/media/video/v4l2-ioctl.c index e1da8fc..cb29e00 100644 --- a/drivers/media/video/v4l2-ioctl.c +++ b/drivers/media/video/v4l2-ioctl.c @@ -207,6 +207,7 @@ static const char *v4l2_ioctls[] = { [_IOC_NR(VIDIOC_S_FBUF)] = "VIDIOC_S_FBUF", [_IOC_NR(VIDIOC_OVERLAY)] = "VIDIOC_OVERLAY", [_IOC_NR(VIDIOC_QBUF)] = "VIDIOC_QBUF",
- [_IOC_NR(VIDIOC_EXPBUF)] = "VIDIOC_EXPBUF", [_IOC_NR(VIDIOC_DQBUF)] = "VIDIOC_DQBUF", [_IOC_NR(VIDIOC_STREAMON)] = "VIDIOC_STREAMON", [_IOC_NR(VIDIOC_STREAMOFF)] = "VIDIOC_STREAMOFF",
@@ -932,6 +933,16 @@ static long __video_do_ioctl(struct file *file, dbgbuf(cmd, vfd, p); break; }
- case VIDIOC_EXPBUF:
- {
unsigned int *p = arg;if (!ops->vidioc_expbuf)break;ret = ops->vidioc_expbuf(file, fh, *p);break;- } case VIDIOC_DQBUF: { struct v4l2_buffer *p = arg;
diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h index 3c0ade1..448fbed 100644 --- a/include/linux/videodev2.h +++ b/include/linux/videodev2.h @@ -2183,6 +2183,7 @@ struct v4l2_create_buffers { #define VIDIOC_S_FBUF _IOW('V', 11, struct v4l2_framebuffer) #define VIDIOC_OVERLAY _IOW('V', 14, int) #define VIDIOC_QBUF _IOWR('V', 15, struct v4l2_buffer) +#define VIDIOC_EXPBUF _IOWR('V', 16, __u32) #define VIDIOC_DQBUF _IOWR('V', 17, struct v4l2_buffer) #define VIDIOC_STREAMON _IOW('V', 18, int) #define VIDIOC_STREAMOFF _IOW('V', 19, int) diff --git a/include/media/v4l2-ioctl.h b/include/media/v4l2-ioctl.h index 4d1c74a..8201546 100644 --- a/include/media/v4l2-ioctl.h +++ b/include/media/v4l2-ioctl.h @@ -120,6 +120,7 @@ struct v4l2_ioctl_ops { int (*vidioc_reqbufs) (struct file *file, void *fh, struct v4l2_requestbuffers *b); int (*vidioc_querybuf)(struct file *file, void *fh, struct v4l2_buffer *b); int (*vidioc_qbuf) (struct file *file, void *fh, struct v4l2_buffer *b);
int (*vidioc_expbuf) (struct file *file, void *fh, __u32 offset); int (*vidioc_dqbuf) (struct file *file, void *fh, struct v4l2_buffer *b);
int (*vidioc_create_bufs)(struct file *file, void *fh, struct v4l2_create_buffers *b);