Hi Thomasz,
On 03/22/2012 04:46 PM, Laurent Pinchart wrote:
Hi Tomasz,
Thanks for the patch.
On Tuesday 13 March 2012 11:17:02 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.
I know code is more fun to write than documentation, but
Documentation/DocBook/media/v4l will be sad if this patch is merged as-is ;-)
Signed-off-by: Tomasz Stanislawski<t.stanislaws@xxxxxxxxxxx>
Signed-off-by: Kyungmin Park<kyungmin.park@xxxxxxxxxxx>
---
drivers/media/video/v4l2-compat-ioctl32.c | 1 +
drivers/media/video/v4l2-ioctl.c | 11 +++++++++++
include/linux/videodev2.h | 20 ++++++++++++++++++++
include/media/v4l2-ioctl.h | 2 ++
4 files changed, 34 insertions(+), 0 deletions(-)
diff --git a/drivers/media/video/v4l2-compat-ioctl32.c
b/drivers/media/video/v4l2-compat-ioctl32.c index e6f67aa..fd157cb 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 74cab51..a125016 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",
@@ -938,6 +939,16 @@ static long __video_do_ioctl(struct file *file,
dbgbuf(cmd, vfd, p);
break;
}
+ case VIDIOC_EXPBUF:
+ {
+ struct v4l2_exportbuffer *p = arg;
+
+ if (!ops->vidioc_expbuf)
+ break;
+
+ ret = ops->vidioc_expbuf(file, fh, p);
You can pass arg to ops->vidioc_expbuf() directly, there's no need to create a
struct v4l2_exportbuffer *p variable.
+ break;
+ }
case VIDIOC_DQBUF:
{
struct v4l2_buffer *p = arg;
diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
index bb6844e..e71c787 100644
--- a/include/linux/videodev2.h
+++ b/include/linux/videodev2.h
@@ -680,6 +680,25 @@ struct v4l2_buffer {
#define V4L2_BUF_FLAG_NO_CACHE_INVALIDATE 0x0800
#define V4L2_BUF_FLAG_NO_CACHE_CLEAN 0x1000
+/**
+ * struct v4l2_exportbuffer - export of video buffer as DMABUF file
descriptor
+ *
+ * @fd: file descriptor associated with DMABUF (set by driver)
+ * @mem_offset: for non-multiplanar buffers with memory ==
V4L2_MEMORY_MMAP;
I don't think we will ever support exporting anything else than
V4L2_MEMORY_MMAP buffers. What will happen for multiplanar buffers ?
+ * offset from the start of the device memory for this plane,
+ * (or a "cookie" that should be passed to mmap() as offset)
+ *
Shouldn't the mem_offset field always be set to the mmap cookie value ? I'm a
bit confused by the "or" part, it seems to have been copied from the
v4l2_buffer documentation directly. We should clarify that.
+ * Contains data used for exporting a video buffer as DMABUF file
+ * descriptor. Uses the same 'cookie' as mmap() syscall. All reserved
fields
+ * must be set to zero.
+ */
+struct v4l2_exportbuffer {
+ __u32 fd;
+ __u32 reserved0;
Why is there a reserved field here ?
+1 to Laurent. Any particular need for reserved0 and reserved[13] below?
I think one void user pointer is sufficient even for future need.
+ __u32 mem_offset;
+ __u32 reserved[13];
+};
+
Also, what is the reason for returning the fd through this structure? To
keep it aligned with other v4l2 calls? I liked(or now hate making change
in the app) how it was being returned through the ioctl in your last patch.
/*
* O V E R L A Y P R E V I E W
*/
@@ -2303,6 +2322,7 @@ 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, struct v4l2_exportbuffer)
#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 4df031a..d8716c6f 100644
--- a/include/media/v4l2-ioctl.h
+++ b/include/media/v4l2-ioctl.h
@@ -120,6 +120,8 @@ 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,
+ struct v4l2_exportbuffer *e);
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);
Regards,
Subash
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