Re: [RFC PATCH] capture-example: allow V4L2_PIX_FMT_GREY with USERPTR

[Mauro Carvalho Chehab <mchehab@redhat.com>]

Em 28-06-2011 11:23, Michael Jones escreveu:
> There is an assumption that the format coming from the device
> needs 2 bytes per pixel, which is not the case when the device
> delivers e.g. V4L2_PIX_FMT_GREY. This doesn't manifest itself with
> IO_METHOD_MMAP because init_mmap() (the default) doesn't take
> sizeimage as an argument.
> 
> Signed-off-by: Michael Jones <michael.jones@matrix-vision.de>
> ---
> 
> This same issue would apply to other formats which have 1 byte per pixel,
> this patch only fixes it for GREY.  Is this OK for now, or does somebody
> have a better suggestion for supporting other formats as well?

Well, just rely on the bytesperline provided by the driver should be enough.
Devices should be returning it on a consistent way.

Regards,
Mauro

> 
>  contrib/test/capture-example.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/contrib/test/capture-example.c b/contrib/test/capture-example.c
> index 3852c58..0eb5235 100644
> --- a/contrib/test/capture-example.c
> +++ b/contrib/test/capture-example.c
> @@ -416,6 +416,7 @@ static void init_device(void)
>  	struct v4l2_crop crop;
>  	struct v4l2_format fmt;
>  	unsigned int min;
> +	unsigned int bytes_per_pixel;
>  
>  	if (-1 == xioctl(fd, VIDIOC_QUERYCAP, &cap)) {
>  		if (EINVAL == errno) {
> @@ -519,7 +520,8 @@ static void init_device(void)
>  	}
>  
>  	/* Buggy driver paranoia. */
> -	min = fmt.fmt.pix.width * 2;
> +	bytes_per_pixel = fmt.fmt.pix.pixelformat == V4L2_PIX_FMT_GREY ? 1 : 2;
> +	min = fmt.fmt.pix.width * bytes_per_pixel;
>  	if (fmt.fmt.pix.bytesperline < min)
>  		fmt.fmt.pix.bytesperline = min;
>  	min = fmt.fmt.pix.bytesperline * fmt.fmt.pix.height;