Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.36 as permitted sender) client-ip=23.128.96.36;
Message-ID: <1823eb2d-49bf-40b1-8952-c084fe2f8a88@collabora.com>
Date:   Mon, 4 Dec 2023 16:25:39 +0200
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v2 03/36] media: microchip: Remove useless setting of
 min_buffers_needed
Content-Language: en-US
To:     Hans Verkuil <hverkuil@xs4all.nl>,
        Benjamin Gaignard <benjamin.gaignard@collabora.com>,
        mchehab@kernel.org, tfiga@chromium.org, m.szyprowski@samsung.com,
        matt.ranostay@konsulko.com
Cc:     linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
        linux-staging@lists.linux.dev, kernel@collabora.com
References: <20231204132323.22811-1-benjamin.gaignard@collabora.com>
 <20231204132323.22811-4-benjamin.gaignard@collabora.com>
 <ab06b2c0-a290-46cd-9d97-3f9f6e3bbb36@xs4all.nl>
From:   Eugen Hristev <eugen.hristev@collabora.com>
In-Reply-To: <ab06b2c0-a290-46cd-9d97-3f9f6e3bbb36@xs4all.nl>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 12/4/23 16:03, Hans Verkuil wrote:
> On 04/12/2023 14:22, Benjamin Gaignard wrote:
>> This driver uses min_buffers_needed which vb2 uses to ensure
>> start_streaming is called when at least 'min_buffers_needed'
>> buffers are queued. However, this driver doesn't need this,
>> it can stream fine without any buffers queued.
>> Just drop this unnecessary restriction.
>>
>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
>> CC: Eugen Hristev <eugen.hristev@collabora.com>
>> ---
>>  drivers/media/platform/microchip/microchip-isc-base.c | 1 -
>>  1 file changed, 1 deletion(-)
>>
>> diff --git a/drivers/media/platform/microchip/microchip-isc-base.c b/drivers/media/platform/microchip/microchip-isc-base.c
>> index 3fba0e2844b6..63c39981f47a 100644
>> --- a/drivers/media/platform/microchip/microchip-isc-base.c
>> +++ b/drivers/media/platform/microchip/microchip-isc-base.c
>> @@ -1821,7 +1821,6 @@ static int isc_async_complete(struct v4l2_async_notifier *notifier)
>>  	q->mem_ops		= &vb2_dma_contig_memops;
>>  	q->timestamp_flags	= V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
>>  	q->lock			= &isc->lock;
>> -	q->min_buffers_needed	= 1;
> 
> I don't think this can be dropped. Looking at the isc_start_streaming() function
> it expects to have at least one buffer queued.

Stream goes frame by frame with DMA directly into the buffers.
Will this still work without any buffers queued ?

> 
> Regards,
> 
> 	Hans
> 
>>  	q->dev			= isc->dev;
>>  
>>  	ret = vb2_queue_init(q);
>