Hi Hans,
Thank you for the patch.
On Wed, Aug 03, 2022 at 12:04:02PM +0200, Hans Verkuil wrote:
> The V4L2_CAP_ASYNCIO capability was never implemented (and in fact
> it isn't clear what it is supposed to do in the first place).
>
> Drop it from the capabilities list. Keep it in videodev2.h defined
> to 0 with the other defines under ifndef __KERNEL__ for backwards
> compatibility.
>
> This will free up a capability bit for other future uses. And having
> an unused and undefined I/O method is just plain confusing.
>
> Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
> ---
> Documentation/userspace-api/media/v4l/async.rst | 9 ---------
> Documentation/userspace-api/media/v4l/dev-raw-vbi.rst | 2 +-
> Documentation/userspace-api/media/v4l/dev-sdr.rst | 2 +-
> Documentation/userspace-api/media/v4l/dev-sliced-vbi.rst | 2 +-
> Documentation/userspace-api/media/v4l/hist-v4l2.rst | 2 +-
> Documentation/userspace-api/media/v4l/io.rst | 4 +---
> .../userspace-api/media/v4l/vidioc-querycap.rst | 3 ---
> include/uapi/linux/videodev2.h | 2 +-
> 8 files changed, 6 insertions(+), 20 deletions(-)
> delete mode 100644 Documentation/userspace-api/media/v4l/async.rst
>
> diff --git a/Documentation/userspace-api/media/v4l/async.rst b/Documentation/userspace-api/media/v4l/async.rst
> deleted file mode 100644
> index d6960ff5c382..000000000000
> --- a/Documentation/userspace-api/media/v4l/async.rst
> +++ /dev/null
> @@ -1,9 +0,0 @@
> -.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
> -
> -.. _async:
> -
> -****************
> -Asynchronous I/O
> -****************
> -
> -This method is not defined yet.
> diff --git a/Documentation/userspace-api/media/v4l/dev-raw-vbi.rst b/Documentation/userspace-api/media/v4l/dev-raw-vbi.rst
> index 58f97c3a7792..2bec20d87928 100644
> --- a/Documentation/userspace-api/media/v4l/dev-raw-vbi.rst
> +++ b/Documentation/userspace-api/media/v4l/dev-raw-vbi.rst
> @@ -41,7 +41,7 @@ Devices supporting the raw VBI capturing or output API set the
> in the ``capabilities`` field of struct
> :c:type:`v4l2_capability` returned by the
> :ref:`VIDIOC_QUERYCAP` ioctl. At least one of the
> -read/write, streaming or asynchronous I/O methods must be supported. VBI
> +read/write or streaming I/O methods must be supported. VBI
> devices may or may not have a tuner or modulator.
>
> Supplemental Functions
> diff --git a/Documentation/userspace-api/media/v4l/dev-sdr.rst b/Documentation/userspace-api/media/v4l/dev-sdr.rst
> index 928884dfe09d..dfdeddbca41f 100644
> --- a/Documentation/userspace-api/media/v4l/dev-sdr.rst
> +++ b/Documentation/userspace-api/media/v4l/dev-sdr.rst
> @@ -34,7 +34,7 @@ Devices supporting the SDR transmitter interface set the
> device has an Digital to Analog Converter (DAC), which is a mandatory
> element for the SDR transmitter.
>
> -At least one of the read/write, streaming or asynchronous I/O methods
> +At least one of the read/write or streaming I/O methods
> must be supported.
>
>
> diff --git a/Documentation/userspace-api/media/v4l/dev-sliced-vbi.rst b/Documentation/userspace-api/media/v4l/dev-sliced-vbi.rst
> index 97ec2b115c71..44415822c7c5 100644
> --- a/Documentation/userspace-api/media/v4l/dev-sliced-vbi.rst
> +++ b/Documentation/userspace-api/media/v4l/dev-sliced-vbi.rst
> @@ -36,7 +36,7 @@ Devices supporting the sliced VBI capturing or output API set the
> respectively, in the ``capabilities`` field of struct
> :c:type:`v4l2_capability` returned by the
> :ref:`VIDIOC_QUERYCAP` ioctl. At least one of the
> -read/write, streaming or asynchronous :ref:`I/O methods <io>` must be
> +read/write or streaming :ref:`I/O methods <io>` must be
> supported. Sliced VBI devices may have a tuner or modulator.
>
> Supplemental Functions
> diff --git a/Documentation/userspace-api/media/v4l/hist-v4l2.rst b/Documentation/userspace-api/media/v4l/hist-v4l2.rst
> index 28a2750d5c8c..dbc04374dc22 100644
> --- a/Documentation/userspace-api/media/v4l/hist-v4l2.rst
> +++ b/Documentation/userspace-api/media/v4l/hist-v4l2.rst
> @@ -316,7 +316,7 @@ This unnamed version was finally merged into Linux 2.5.46.
> There are new fields to identify the driver, a new RDS device
> function ``V4L2_CAP_RDS_CAPTURE``, the ``V4L2_CAP_AUDIO`` flag
> indicates if the device has any audio connectors, another I/O
> - capability ``V4L2_CAP_ASYNCIO`` can be flagged. In response to these
> + capability V4L2_CAP_ASYNCIO can be flagged. In response to these
> changes the ``type`` field became a bit set and was merged into the
> ``flags`` field. ``V4L2_FLAG_TUNER`` was renamed to
> ``V4L2_CAP_TUNER``, ``V4L2_CAP_VIDEO_OVERLAY`` replaced
> diff --git a/Documentation/userspace-api/media/v4l/io.rst b/Documentation/userspace-api/media/v4l/io.rst
> index ce0cece6f35f..4b1964df9d73 100644
> --- a/Documentation/userspace-api/media/v4l/io.rst
> +++ b/Documentation/userspace-api/media/v4l/io.rst
> @@ -17,8 +17,7 @@ read or write will fail at any time.
>
> Other methods must be negotiated. To select the streaming I/O method
> with memory mapped or user buffers applications call the
> -:ref:`VIDIOC_REQBUFS` ioctl. The asynchronous I/O
> -method is not defined yet.
> +:ref:`VIDIOC_REQBUFS` ioctl.
>
> Video overlay can be considered another I/O method, although the
> application does not directly receive the image data. It is selected by
> @@ -46,6 +45,5 @@ The following sections describe the various I/O methods in more detail.
> mmap
> userp
> dmabuf
> - async
> buffer
> field-order
> diff --git a/Documentation/userspace-api/media/v4l/vidioc-querycap.rst b/Documentation/userspace-api/media/v4l/vidioc-querycap.rst
> index 63e23f6f95ee..6c57b8428356 100644
> --- a/Documentation/userspace-api/media/v4l/vidioc-querycap.rst
> +++ b/Documentation/userspace-api/media/v4l/vidioc-querycap.rst
> @@ -244,9 +244,6 @@ specification the ioctl returns an ``EINVAL`` error code.
> - 0x01000000
> - The device supports the :c:func:`read()` and/or
> :c:func:`write()` I/O methods.
> - * - ``V4L2_CAP_ASYNCIO``
> - - 0x02000000
> - - The device supports the :ref:`asynchronous <async>` I/O methods.
> * - ``V4L2_CAP_STREAMING``
> - 0x04000000
> - The device supports the :ref:`streaming <mmap>` I/O method.
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 01e630f2ec78..1af12e5928aa 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -502,7 +502,6 @@ struct v4l2_capability {
> #define V4L2_CAP_META_CAPTURE 0x00800000 /* Is a metadata capture device */
>
> #define V4L2_CAP_READWRITE 0x01000000 /* read/write systemcalls */
> -#define V4L2_CAP_ASYNCIO 0x02000000 /* async I/O */
> #define V4L2_CAP_STREAMING 0x04000000 /* streaming I/O ioctls */
> #define V4L2_CAP_META_OUTPUT 0x08000000 /* Is a metadata output device */
>
> @@ -2682,6 +2681,7 @@ struct v4l2_create_buffers {
> #ifndef __KERNEL__
> #define V4L2_PIX_FMT_HM12 V4L2_PIX_FMT_NV12_16L16
> #define V4L2_PIX_FMT_SUNXI_TILED_NV12 V4L2_PIX_FMT_NV12_32L32
> +#define V4L2_CAP_ASYNCIO 0
I'm fine dropping V4L2_CAP_ASYNCIO, but this particular change doesn't
sound right. Applications that would do, for instance,
if (caps & V4L2_CAP_ASYNCIO) {
...
}
could now get a warning from the compiler that the condition is always
false.
> #endif
>
> #endif /* _UAPI__LINUX_VIDEODEV2_H */
--
Regards,
Laurent Pinchart
