Re: [PATCH 5/7] media: cedrus: h265: Add a couple of error checks

[Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>]

On Mon, Jun 20, 2022 at 07:55:15PM +0200, Jernej Skrabec wrote:
> Now that we have infrastructure for reporting errors, let's add two
> checks, which will make sure slice can be actually decoded.
> 
> Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
> ---
>  drivers/staging/media/sunxi/cedrus/cedrus_h265.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> index cfde4ccf6011..99020b9f9ff8 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c

Now that you've allowed setup to fail, I would suggest
to have some documentation/comments on struct cedrus_dec_ops,
to set the expectation/rules for each ops, including the
call paths for each operation, which of them are allowed to sleep,
etc.

> @@ -435,9 +435,17 @@ static int cedrus_h265_setup(struct cedrus_ctx *ctx, struct cedrus_run *run)
>  	 * instead of start of slice data. Padding is 8 bits at most (one bit set to 1 and
>  	 * at most seven bits set to 0), so we have to inspect only one byte before slice data.
>  	 */
> +
> +	if (slice_params->data_byte_offset == 0)
> +		return -EOPNOTSUPP;
> +

AFAICS, cedrus_h265_setup is called from .device_run.
We've been discussing control validation before, and I think the
ideal place to do that is v4l2_ctrl_ops.s_ctrl, if that's
at all possible.

Driver's mem2mem device_run are executed in the context
of a work_struct and the failure won't really get reported
up the stack.

>  	padding = (u8 *)vb2_plane_vaddr(&run->src->vb2_buf, 0) +
>  		slice_params->data_byte_offset - 1;
>  
> +	/* at least one bit must be set in that byte */
> +	if (*padding == 0)
> +		return -EINVAL;
> +

Maybe this is something to check at cedrus_buf_prepare(),
when the buffer is queued?

Thanks,
Ezequiel

>  	for (count = 0; count < 8; count++)
>  		if (*padding & (1 << count))
>  			break;
> -- 
> 2.36.1
>