linux-kernel - Re: [PATCH v3 09/24] media: v4l2: Trace calculated p/b0/b1 initial reflist

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Date:   Fri, 22 Apr 2022 09:26:34 +0200
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Nicolas Dufresne <nicolas.dufresne@...labora.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     kernel@...labora.com, linux-kernel@...r.kernel.org,
        Sebastian Fricke <sebastian.fricke@...labora.com>,
        linux-media@...r.kernel.org
Subject: Re: [PATCH v3 09/24] media: v4l2: Trace calculated p/b0/b1 initial
 reflist

On 05/04/2022 22:44, Nicolas Dufresne wrote:
> Add debug print statements to print the content of P & B reference
> lists, to verify that the ordering of the generated reference lists is
> correct. This is especially important for the field decoding mode,
> where sorting is more complex.
> 
> Signed-off-by: Nicolas Dufresne <nicolas.dufresne@...labora.com>
> Tested-by: Sebastian Fricke <sebastian.fricke@...labora.com>
> Reviewed-by: Sebastian Fricke <sebastian.fricke@...labora.com>
> ---
>  drivers/media/v4l2-core/v4l2-h264.c | 86 +++++++++++++++++++++++++++++
>  1 file changed, 86 insertions(+)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-h264.c b/drivers/media/v4l2-core/v4l2-h264.c
> index 38d8dbda0045..bcf9b7774560 100644
> --- a/drivers/media/v4l2-core/v4l2-h264.c
> +++ b/drivers/media/v4l2-core/v4l2-h264.c
> @@ -241,6 +241,87 @@ static int v4l2_h264_b1_ref_list_cmp(const void *ptra, const void *ptrb,
>  	return poca < pocb ? -1 : 1;
>  }
>  
> +static char ref_type_to_char (u8 ref_type)

Spurious space before (.

Odd that checkpatch didn't catch that.

> +{
> +	switch (ref_type) {
> +	case V4L2_H264_FRAME_REF:
> +		return 'f';
> +	case V4L2_H264_TOP_FIELD_REF:
> +		return 't';
> +	case V4L2_H264_BOTTOM_FIELD_REF:
> +		return 'b';
> +	}
> +
> +	return '?';
> +}
> +
> +static const char *format_ref_list_p(const struct v4l2_h264_reflist_builder *builder,
> +				     struct v4l2_h264_reference *reflist,
> +				     char *out_str, const int len)
> +{
> +	int n = 0, i;
> +
> +	n += snprintf(out_str + n, len - n, "|");
> +
> +	for (i = 0; i < builder->num_valid; i++) {
> +		/* this is pic_num for frame and frame_num (wrapped) for field,
> +		 * but for frame pic_num is equal to frame_num (wrapped).
> +		 */
> +		int frame_num = builder->refs[reflist[i].index].frame_num;
> +		bool longterm = builder->refs[reflist[i].index].longterm;
> +
> +		n += scnprintf(out_str + n, len - n, "%i%c%c|",
> +			       frame_num, longterm ? 'l' : 's',
> +			       ref_type_to_char (reflist[i].fields));
> +	}
> +
> +	return out_str;
> +}
> +
> +static void print_ref_list_p(const struct v4l2_h264_reflist_builder *builder,
> +			     struct v4l2_h264_reference *reflist)
> +{
> +	char buf[1024];
> +
> +	pr_debug("ref_pic_list_p (cur_poc %u%c) %s\n",
> +		 builder->cur_pic_order_count,
> +		 ref_type_to_char(builder->cur_pic_fields),
> +		 format_ref_list_p(builder, reflist, buf, sizeof(buf)));
> +}
> +
> +static const char *format_ref_list_b(const struct v4l2_h264_reflist_builder *builder,
> +				     struct v4l2_h264_reference *reflist,
> +				     char *out_str, const int len)
> +{
> +	int n = 0, i;
> +
> +	n += snprintf(out_str + n, len - n, "|");
> +
> +	for (i = 0; i < builder->num_valid; i++) {
> +		int frame_num = builder->refs[reflist[i].index].frame_num;
> +		u32 poc = v4l2_h264_get_poc(builder, reflist + i);
> +		bool longterm = builder->refs[reflist[i].index].longterm;
> +
> +		n += scnprintf(out_str + n, len - n, "%i%c%c|",
> +			       longterm ? frame_num : poc,
> +			       longterm ? 'l' : 's',
> +			       ref_type_to_char(reflist[i].fields));
> +	}
> +
> +	return out_str;
> +}
> +
> +static void print_ref_list_b(const struct v4l2_h264_reflist_builder *builder,
> +			     struct v4l2_h264_reference *reflist, u8 list_num)
> +{
> +	char buf[1024];

I really don't like placing 1024 bytes on the stack. Can you find another way
of doing this? Perhaps using pr_cont or writing each format_ref_list item
on a separate line.

Regards,

	Hans

> +
> +	pr_debug("ref_pic_list_b%u (cur_poc %u%c) %s",
> +		 list_num, builder->cur_pic_order_count,
> +		 ref_type_to_char (builder->cur_pic_fields),
> +		 format_ref_list_b(builder, reflist, buf, sizeof(buf)));
> +}
> +
>  /**
>   * v4l2_h264_build_p_ref_list() - Build the P reference list
>   *
> @@ -261,6 +342,8 @@ v4l2_h264_build_p_ref_list(const struct v4l2_h264_reflist_builder *builder,
>  	       sizeof(builder->unordered_reflist[0]) * builder->num_valid);
>  	sort_r(reflist, builder->num_valid, sizeof(*reflist),
>  	       v4l2_h264_p_ref_list_cmp, NULL, builder);
> +
> +	print_ref_list_p(builder, reflist);
>  }
>  EXPORT_SYMBOL_GPL(v4l2_h264_build_p_ref_list);
>  
> @@ -296,6 +379,9 @@ v4l2_h264_build_b_ref_lists(const struct v4l2_h264_reflist_builder *builder,
>  	if (builder->num_valid > 1 &&
>  	    !memcmp(b1_reflist, b0_reflist, builder->num_valid))
>  		swap(b1_reflist[0], b1_reflist[1]);
> +
> +	print_ref_list_b(builder, b0_reflist, 0);
> +	print_ref_list_b(builder, b1_reflist, 1);
>  }
>  EXPORT_SYMBOL_GPL(v4l2_h264_build_b_ref_lists);
>