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Message-ID: <ca8b1403-ca58-a4b4-d2e2-1c682b5f0adb@xs4all.nl>
Date: Fri, 22 Apr 2022 18:33:54 +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 22/04/2022 16:58, Nicolas Dufresne wrote:
> Le vendredi 22 avril 2022 à 09:26 +0200, Hans Verkuil a écrit :
>> 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.
>
> Thanks, I was strongly discourage of using pr_cont (which was my first
> approach). Rationales are well covered on LKLM and in the pr_cont documentation,
> so I won't say more then its not visually thread safe.
>
> I would like to decline the second proposition, as having the lists spread out
> on up to 32 lines will make the trace very hard to use. What I may suggest, as I
> would really prefer keeping this trace useful, is to use an allocation instead.
> The performance does not matter, and I explicitly call this function inside the
> pr_debug call so it can be compiled out.
Allocation is probably best here.
Regards,
Hans
>
> My last resort otherwise would be to use 32 %s formaters, and pass each of the
> possible 32 entry (or empty string "") manually.
>
> let me know what you believe is acceptable for you,
> Nicolas
>
>>
>> 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);
>>>
>>
>
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