Re: [PATCH RESEND] libv4lconvert: Fix a regression when converting from Y10B

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 06/16/2014 05:00 PM, Antonio Ospite wrote:
> Fix a regression introduced in commit
> efc29f1764a30808ebf7b3e1d9bfa27b909bf641 (libv4lconvert: Reject too
> short source buffer before accessing it).
> 
> The old code:
> 
> case V4L2_PIX_FMT_Y10BPACK:
> 	...
> 	if (result == 0 && src_size < (width * height * 10 / 8)) {
> 		V4LCONVERT_ERR("short y10b data frame\n");
> 		errno = EPIPE;
> 		result = -1;
> 	}
> 	...
> 
> meant to say "If the conversion was *successful* _but_ the frame size
> was invalid, then take the error path", but in
> efc29f1764a30808ebf7b3e1d9bfa27b909bf641 this (maybe weird) logic was
> misunderstood and v4lconvert_convert_pixfmt() was made to return an
> error even in the case of a successful conversion from Y10B.
> 
> Fix the check, and now print only the message letting the errno and the
> result from the conversion routines to be propagated to the caller.
> 
> Signed-off-by: Antonio Ospite <ao2@ao2.it>
> Cc: Gregor Jasny <gjasny@googlemail.com>

Thanks for the patch, but: ...

> ---
>  lib/libv4lconvert/libv4lconvert.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/lib/libv4lconvert/libv4lconvert.c b/lib/libv4lconvert/libv4lconvert.c
> index c49d30d..50d6906 100644
> --- a/lib/libv4lconvert/libv4lconvert.c
> +++ b/lib/libv4lconvert/libv4lconvert.c
> @@ -1052,11 +1052,8 @@ static int v4lconvert_convert_pixfmt(struct v4lconvert_data *data,
>  							   width, height);
>  			break;
>  		}
> -		if (result == 0) {
> +		if (result != 0)
>  			V4LCONVERT_ERR("y10b conversion failed\n");
> -			errno = EPIPE;
> -			result = -1;
> -		}
>  		break;
>  
>  	case V4L2_PIX_FMT_RGB565:

Why print a message here at all in the != 0 case? In the old code before commit
efc29f1764 you did not print an error when v4lconvert_y10b_to_... failed, so
I assume that that already does a V4LCONVERT_ERR in that case. So why do it a
second time with a less precise error message here?

So I believe that the proper fix would be to just remove the entire block instead
of flipping the test and keeping the V4LCONVERT_ERR. Please send a new version
with this fixed, then I'll merge it asap.

Regards,

Hans