linux-kernel - Re: [PATCH v3 13/23] media: iris: Send V4L2_BUF_FLAG

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Message-ID: <36757fb1-b1a9-5b49-c5b8-62cde4dea1c5@quicinc.com>
Date: Sun, 4 May 2025 20:53:01 +0530
From: Dikshita Agarwal <quic_dikshita@...cinc.com>
To: Nicolas Dufresne <nicolas.dufresne@...labora.com>,
        Vikash Garodia
	<quic_vgarodia@...cinc.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        "Mauro Carvalho Chehab" <mchehab@...nel.org>,
        Stefan Schmidt
	<stefan.schmidt@...aro.org>,
        Hans Verkuil <hverkuil@...all.nl>,
        "Bjorn
 Andersson" <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        "Rob Herring" <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        "Conor Dooley" <conor+dt@...nel.org>
CC: Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Dmitry Baryshkov
	<dmitry.baryshkov@....qualcomm.com>,
        Neil Armstrong
	<neil.armstrong@...aro.org>,
        <linux-media@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <20250417-topic-sm8x50-iris-v10-v7-0-f020cb1d0e98@...aro.org>,
        <20250424-qcs8300_iris-v5-0-f118f505c300@...cinc.com>
Subject: Re: [PATCH v3 13/23] media: iris: Send V4L2_BUF_FLAG_ERROR for
 buffers with 0 filled length



On 5/3/2025 9:39 PM, Nicolas Dufresne wrote:
> Hi Dikshita,
> 
> Le vendredi 02 mai 2025 à 00:43 +0530, Dikshita Agarwal a écrit :
>> Firmware sends buffers with 0 filled length which needs to be dropped,
>> to achieve the same, add V4L2_BUF_FLAG_ERROR to such buffers.
>> Also make sure:
>> - These 0 length buffers are not returned as result of flush.
>> - Its not a buffer with LAST flag enabled which will also have 0 filled
>>   length.
> 
> This message is quite vague, is this about capture or output buffers ?
> If its output buffers that don't produce capture, I don't see why they
> have to be flagged as errors, or why the payload size matter. Then, if
> its about assigned capture buffers that did not get used in the end, you
> should put them back in the queue instead of returning them to user
> space.
> 
> Returning a capture buffers to userspace should only be used if a frame
> could not be produced. That imply copying the cookie timestamp from the
> src buffers into the capture buffer. Please make sure you don't endup
> returning fake erorrs to userspace, which may lead to some frame
> metadata being dropped erroneously.
> 
The capture buffers which I am trying to handle here are of 0 byteused
which means they don't have any valid data and they have the timestamp
copied from src buffers.
How these buffers will be handled by client? if we don't associate error
flag to such buffers?

Thanks,
Dikshita
> Nicolas
> 
>>
>> Acked-by: Vikash Garodia <quic_vgarodia@...cinc.com>
>> Signed-off-by: Dikshita Agarwal <quic_dikshita@...cinc.com>
>> ---
>>  drivers/media/platform/qcom/iris/iris_hfi_gen2_response.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/drivers/media/platform/qcom/iris/iris_hfi_gen2_response.c
>> b/drivers/media/platform/qcom/iris/iris_hfi_gen2_response.c
>> index 4488540d1d41..3bb326843a7b 100644
>> --- a/drivers/media/platform/qcom/iris/iris_hfi_gen2_response.c
>> +++ b/drivers/media/platform/qcom/iris/iris_hfi_gen2_response.c
>> @@ -378,6 +378,12 @@ static int iris_hfi_gen2_handle_output_buffer(struct iris_inst *inst,
>>  
>>  	buf->flags = iris_hfi_gen2_get_driver_buffer_flags(inst, hfi_buffer->flags);
>>  
>> +	if (!buf->data_size && inst->state == IRIS_INST_STREAMING &&
>> +	    !(hfi_buffer->flags & HFI_BUF_FW_FLAG_LAST) &&
>> +	    !(inst->sub_state & IRIS_INST_SUB_DRC)) {
>> +		buf->flags |= V4L2_BUF_FLAG_ERROR;
>> +	}
>> +
>>  	return 0;
>>  }
>>