[1/1] v4l: Add macros for printing V4L 4cc values

  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_to_conv provides the actual
arguments for that conversion specifier.

These macros are useful in both user and kernel code, therefore put them
into videodev2.h.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
---
 include/uapi/linux/videodev2.h | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)
  

Em Wed,  4 Apr 2018 16:02:10 +0300
Sakari Ailus <sakari.ailus@linux.intel.com> escreveu:

> 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_to_conv provides the actual
> arguments for that conversion specifier.
> 
> These macros are useful in both user and kernel code, therefore put them
> into videodev2.h.
> 
> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> ---
>  include/uapi/linux/videodev2.h | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index caec178..93184929 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -82,6 +82,31 @@
>  	((__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) | (1 << 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_to_conv macro.
> + *
> + * Example ("format" is the V4L2 pixelformat in __u32):
> + *
> + * printf("V4L2 format is: " v4l2_fourcc_conv "\n", v4l2_fourcc_to_conv(format);
> + */
> +#define v4l2_fourcc_conv "%c%c%c%c%s"
> +
> +/**
> + * v4l2_fourcc_to_conv - 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.
> + */
> +#define v4l2_fourcc_to_conv(fourcc)					\
> +	(fourcc) & 0x7f, ((fourcc) >> 8) & 0x7f, ((fourcc) >> 16) & 0x7f, \
> +	((fourcc) >> 24) & 0x7f, (fourcc) & (1 << 31) ? "-BE" : ""
> +

IMO, it doesn't make sense to have this at uAPI.


Thanks,
Mauro