linux-kernel - Re: [PATCH] vb2: Allow STREAMOFF for io emulator

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Date:	Tue, 8 Oct 2013 09:58:23 +0200
From:	Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
To:	Marek Szyprowski <m.szyprowski@...sung.com>
Cc:	Pawel Osciak <pawel@...iak.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Mauro Carvalho Chehab <m.chehab@...sung.com>,
	linux-media <linux-media@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] vb2: Allow STREAMOFF for io emulator

Hi Marek

Thanks for your comments. I was just trying to find a way to stop
streaming while in read/write mode without having to close the
descriptor. I thought reusing streamoff was more clever than creating
a new ioctl.

Thanks!

On Tue, Oct 8, 2013 at 9:22 AM, Marek Szyprowski
<m.szyprowski@...sung.com> wrote:
> Hello,
>
>
> On 2013-10-04 15:49, Ricardo Ribalda Delgado wrote:
>>
>> A video device opened and streaming in io emulator mode can only stop
>> streamming if its file descriptor is closed.
>>
>> There are some parameters that can only be changed if the device is not
>> streaming. Also, the power consumption of a device streaming could be
>> different than one not streaming.
>>
>> With this patch a video device opened in io emulator can be stopped on
>> demand.
>>
>> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
>
>
> Read/write-based io mode must not be mixed with ioctrl-based IO, so I really
> cannot accept this patch. Check V4L2 documentation for more details.
>
>
>> ---
>>   drivers/media/v4l2-core/videobuf2-core.c | 11 ++++++-----
>>   1 file changed, 6 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/media/v4l2-core/videobuf2-core.c
>> b/drivers/media/v4l2-core/videobuf2-core.c
>> index 9fc4bab..097fba8 100644
>> --- a/drivers/media/v4l2-core/videobuf2-core.c
>> +++ b/drivers/media/v4l2-core/videobuf2-core.c
>> @@ -1686,6 +1686,7 @@ int vb2_streamon(struct vb2_queue *q, enum
>> v4l2_buf_type type)
>>   }
>>   EXPORT_SYMBOL_GPL(vb2_streamon);
>>   +static int __vb2_cleanup_fileio(struct vb2_queue *q);
>>     /**
>>    * vb2_streamoff - stop streaming
>> @@ -1704,11 +1705,6 @@ EXPORT_SYMBOL_GPL(vb2_streamon);
>>    */
>>   int vb2_streamoff(struct vb2_queue *q, enum v4l2_buf_type type)
>>   {
>> -       if (q->fileio) {
>> -               dprintk(1, "streamoff: file io in progress\n");
>> -               return -EBUSY;
>> -       }
>> -
>>         if (type != q->type) {
>>                 dprintk(1, "streamoff: invalid stream type\n");
>>                 return -EINVAL;
>> @@ -1719,6 +1715,11 @@ int vb2_streamoff(struct vb2_queue *q, enum
>> v4l2_buf_type type)
>>                 return -EINVAL;
>>         }
>>   +     if (q->fileio) {
>> +               __vb2_cleanup_fileio(q);
>> +               return 0;
>> +       }
>> +
>>         /*
>>          * Cancel will pause streaming and remove all buffers from the
>> driver
>>          * and videobuf, effectively returning control over them to
>> userspace.
>
>
> Best regards
> --
> Marek Szyprowski
> Samsung R&D Institute Poland
>



-- 
Ricardo Ribalda
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