On Mon, 2019-09-16 at 12:04 +0200, Hans Verkuil wrote:
> From: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
>
> Add two macros that facilitate printing V4L fourcc values with printf
> family of functions. v4l2_fourcc_conv provides the printf conversion
> specifier for printing formats and v4l2_fourcc_args provides the actual
> arguments for that conversion specifier.
>
> These macros are useful in both user and kernel code whenever you want
> to report a pixelformat, therefore put them into videodev2.h.
>
> Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> [hverkuil-cisco@xxxxxxxxx: rename v4l2_fourcc_to_conv to v4l2_fourcc_args]
> [hverkuil-cisco@xxxxxxxxx: add () around ? : expression]
> [hverkuil-cisco@xxxxxxxxx: add comment about fourcc reuse]
> [hverkuil-cisco@xxxxxxxxx: update Documentation/media/videodev2.h.rst.exceptions]
> ---
> .../media/videodev2.h.rst.exceptions | 2 ++
> include/uapi/linux/videodev2.h | 27 +++++++++++++++++++
> 2 files changed, 29 insertions(+)
>
> diff --git a/Documentation/media/videodev2.h.rst.exceptions b/Documentation/media/videodev2.h.rst.exceptions
> index adeb6b7a15cb..35eb513d82a6 100644
> --- a/Documentation/media/videodev2.h.rst.exceptions
> +++ b/Documentation/media/videodev2.h.rst.exceptions
> @@ -508,6 +508,8 @@ ignore define VIDEO_MAX_FRAME
> ignore define VIDEO_MAX_PLANES
> ignore define v4l2_fourcc
> ignore define v4l2_fourcc_be
> +ignore define v4l2_fourcc_conv
> +ignore define v4l2_fourcc_args
> ignore define V4L2_FIELD_HAS_TOP
> ignore define V4L2_FIELD_HAS_BOTTOM
> ignore define V4L2_FIELD_HAS_BOTH
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 530638dffd93..aa8acbdc88c9 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -82,6 +82,33 @@
> ((__u32)(a) | ((__u32)(b) << 8) | ((__u32)(c) << 16) | ((__u32)(d) << 24))
> #define v4l2_fourcc_be(a, b, c, d) (v4l2_fourcc(a, b, c, d) | (1U << 31))
>
> +/**
> + * v4l2_fourcc_conv - Printf fourcc conversion specifiers for V4L2 formats
> + *
> + * Use as part of the format string. The values are obtained using
> + * @v4l2_fourcc_args macro.
> + *
> + * Example ("format" is the V4L2 pixelformat in __u32):
> + *
> + * printf("V4L2 format is: " v4l2_fourcc_conv "\n", v4l2_fourcc_args(format);
> + */
> +#define v4l2_fourcc_conv "%c%c%c%c%s"
> +
> +/**
> + * v4l2_fourcc_args - Arguments for V4L2 fourcc format conversion
> + *
> + * @fourcc: V4L2 pixelformat, as in __u32
> + *
> + * Yields to a comma-separated list of arguments for printf that matches with
> + * conversion specifiers provided by @v4l2_fourcc_conv.
> + *
> + * Note that v4l2_fourcc_args reuses fourcc, so this can't be an expression
> + * with side-effects.
> + */
> +#define v4l2_fourcc_args(fourcc) \
> + (fourcc) & 0x7f, ((fourcc) >> 8) & 0x7f, ((fourcc) >> 16) & 0x7f, \
> + ((fourcc) >> 24) & 0x7f, ((fourcc) & (1 << 31) ? "-BE" : "")
> +
> /*
> * E N U M S
> */
Reviewed-by: Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx>
Thanks,
Ezequiel
