Re: [PATCH v7 2/6] [media] v4l: add 'unordered' flag to format description ioctl

[Hans Verkuil]

On 01/10/18 17:07, Gustavo Padovan wrote:
> From: Gustavo Padovan 
> 
> For explicit synchronization it important for userspace to know if the
> format being used by the driver can deliver the buffers back to userspace
> in the same order they were queued with QBUF.
> 
> Ordered streams fits nicely in a pipeline with DRM for example, where
> ordered buffer are expected.
> 
> Signed-off-by: Gustavo Padovan 
> ---
>  Documentation/media/uapi/v4l/vidioc-enum-fmt.rst | 3 +++
>  include/uapi/linux/videodev2.h   | 1 +
>  2 files changed, 4 insertions(+)
> 
> diff --git a/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst 
> b/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst
> index 019c513df217..368115f44fc0 100644
> --- a/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst
> +++ b/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst
> @@ -116,6 +116,9 @@ one until ``EINVAL`` is returned.
>- This format is not native to the device but emulated through
>   software (usually libv4l2), where possible try to use a native
>   format instead for better performance.
> +* - ``V4L2_FMT_FLAG_UNORDERED``
> +  - 0x0004
> +  - This is a format that doesn't guarantee timely order of frames.

I'd rephrase this:

"This format doesn't guarantee ordered buffer handling. I.e. the order in
which buffers are dequeued with VIDIOC_DQBUF may be different from the order
in which they were queued with VIDIOC_QBUF."

(Use proper links to VIDIOC_(D)QBUF)

I would also like to see an example of a driver that uses this. The cobalt
driver is a candidate for this.

Regards,

Hans

>  
>  
>  Return Value
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 982718965180..58894cfe9479 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -716,6 +716,7 @@ struct v4l2_fmtdesc {
>  
>  #define V4L2_FMT_FLAG_COMPRESSED 0x0001
>  #define V4L2_FMT_FLAG_EMULATED   0x0002
> +#define V4L2_FMT_FLAG_UNORDERED  0x0004
>  
>   /* Frame Size and frame rate enumeration */
>  /*
> 

Re: [PATCH v7 2/6] [media] v4l: add 'unordered' flag to format description ioctl

[Hans Verkuil]

On 01/10/18 17:07, Gustavo Padovan wrote:
> From: Gustavo Padovan 
> 
> For explicit synchronization it important for userspace to know if the
> format being used by the driver can deliver the buffers back to userspace
> in the same order they were queued with QBUF.
> 
> Ordered streams fits nicely in a pipeline with DRM for example, where
> ordered buffer are expected.
> 
> Signed-off-by: Gustavo Padovan 
> ---
>  Documentation/media/uapi/v4l/vidioc-enum-fmt.rst | 3 +++
>  include/uapi/linux/videodev2.h   | 1 +
>  2 files changed, 4 insertions(+)
> 
> diff --git a/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst 
> b/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst
> index 019c513df217..368115f44fc0 100644
> --- a/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst
> +++ b/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst
> @@ -116,6 +116,9 @@ one until ``EINVAL`` is returned.
>- This format is not native to the device but emulated through
>   software (usually libv4l2), where possible try to use a native
>   format instead for better performance.
> +* - ``V4L2_FMT_FLAG_UNORDERED``
> +  - 0x0004
> +  - This is a format that doesn't guarantee timely order of frames.

I'd rephrase this:

"This format doesn't guarantee ordered buffer handling. I.e. the order in
which buffers are dequeued with VIDIOC_DQBUF may be different from the order
in which they were queued with VIDIOC_QBUF."

(Use proper links to VIDIOC_(D)QBUF)

I would also like to see an example of a driver that uses this. The cobalt
driver is a candidate for this.

Regards,

Hans

>  
>  
>  Return Value
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 982718965180..58894cfe9479 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -716,6 +716,7 @@ struct v4l2_fmtdesc {
>  
>  #define V4L2_FMT_FLAG_COMPRESSED 0x0001
>  #define V4L2_FMT_FLAG_EMULATED   0x0002
> +#define V4L2_FMT_FLAG_UNORDERED  0x0004
>  
>   /* Frame Size and frame rate enumeration */
>  /*
> 

[PATCH v7 2/6] [media] v4l: add 'unordered' flag to format description ioctl

[Gustavo Padovan]

From: Gustavo Padovan 

For explicit synchronization it important for userspace to know if the
format being used by the driver can deliver the buffers back to userspace
in the same order they were queued with QBUF.

Ordered streams fits nicely in a pipeline with DRM for example, where
ordered buffer are expected.

Signed-off-by: Gustavo Padovan 
---
 Documentation/media/uapi/v4l/vidioc-enum-fmt.rst | 3 +++
 include/uapi/linux/videodev2.h   | 1 +
 2 files changed, 4 insertions(+)

diff --git a/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst 
b/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst
index 019c513df217..368115f44fc0 100644
--- a/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst
+++ b/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst
@@ -116,6 +116,9 @@ one until ``EINVAL`` is returned.
   - This format is not native to the device but emulated through
software (usually libv4l2), where possible try to use a native
format instead for better performance.
+* - ``V4L2_FMT_FLAG_UNORDERED``
+  - 0x0004
+  - This is a format that doesn't guarantee timely order of frames.
 
 
 Return Value
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index 982718965180..58894cfe9479 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -716,6 +716,7 @@ struct v4l2_fmtdesc {
 
 #define V4L2_FMT_FLAG_COMPRESSED 0x0001
 #define V4L2_FMT_FLAG_EMULATED   0x0002
+#define V4L2_FMT_FLAG_UNORDERED  0x0004
 
/* Frame Size and frame rate enumeration */
 /*
-- 
2.14.3

[PATCH v7 2/6] [media] v4l: add 'unordered' flag to format description ioctl

[Gustavo Padovan]

From: Gustavo Padovan 

For explicit synchronization it important for userspace to know if the
format being used by the driver can deliver the buffers back to userspace
in the same order they were queued with QBUF.

Ordered streams fits nicely in a pipeline with DRM for example, where
ordered buffer are expected.

Signed-off-by: Gustavo Padovan 
---
 Documentation/media/uapi/v4l/vidioc-enum-fmt.rst | 3 +++
 include/uapi/linux/videodev2.h   | 1 +
 2 files changed, 4 insertions(+)

diff --git a/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst 
b/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst
index 019c513df217..368115f44fc0 100644
--- a/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst
+++ b/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst
@@ -116,6 +116,9 @@ one until ``EINVAL`` is returned.
   - This format is not native to the device but emulated through
software (usually libv4l2), where possible try to use a native
format instead for better performance.
+* - ``V4L2_FMT_FLAG_UNORDERED``
+  - 0x0004
+  - This is a format that doesn't guarantee timely order of frames.
 
 
 Return Value
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index 982718965180..58894cfe9479 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -716,6 +716,7 @@ struct v4l2_fmtdesc {
 
 #define V4L2_FMT_FLAG_COMPRESSED 0x0001
 #define V4L2_FMT_FLAG_EMULATED   0x0002
+#define V4L2_FMT_FLAG_UNORDERED  0x0004
 
/* Frame Size and frame rate enumeration */
 /*
-- 
2.14.3