Re: [PATCH 05/10] v4l: add buffer exporting via dmabuf

[Tomasz Stanislawski <t.stanislaws@samsung.com>]

Hi Mauro.
On 01/23/2012 03:32 PM, Mauro Carvalho Chehab wrote:
> Em 23-01-2012 11:51, Tomasz Stanislawski escreveu:
>> This patch adds extension to V4L2 api. It allow to export a mmap buffer as file
>> descriptor. New ioctl VIDIOC_EXPBUF is added. It takes a buffer offset used by
>> mmap and return a file descriptor on success.
>
> This requires more discussions.
>
> The usecase for this new API seems to replace the features previously provided
> by the overlay mode. There, not only the buffer were exposed to userspace, but
> some control were provided, in order to control the overlay window.

This ioctl was introduced to support exporting of V4L2 buffers via 
dma-buf interface. This framework was little common with overlay mode. 
Could you describe what overlay mode feature is replaced by VIDIOC_EXPBUF?

>
> Please start a separate thread about that, explaining how are you imagining that
> a V4L2 application would use such ioctl.

This patch is essential for full implementation of support for DMABUF 
framework in V4L2. Therefore the patch cannot be moved to separate thread.

Regrads,
Tomasz Stanislawski

>
> Regards,
> Mauro



>
>>
>> Signed-off-by: Tomasz Stanislawski<t.stanislaws@samsung.com>
>> Signed-off-by: Kyungmin Park<kyungmin.park@samsung.com>
>> ---
>>   drivers/media/video/v4l2-compat-ioctl32.c |    1 +
>>   drivers/media/video/v4l2-ioctl.c          |   11 +++++++++++
>>   include/linux/videodev2.h                 |    1 +
>>   include/media/v4l2-ioctl.h                |    1 +
>>   4 files changed, 14 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/media/video/v4l2-compat-ioctl32.c b/drivers/media/video/v4l2-compat-ioctl32.c
>> index c68531b..0f18b5e 100644
>> --- a/drivers/media/video/v4l2-compat-ioctl32.c
>> +++ b/drivers/media/video/v4l2-compat-ioctl32.c
>> @@ -954,6 +954,7 @@ long v4l2_compat_ioctl32(struct file *file, unsigned int cmd, unsigned long arg)
>>   	case VIDIOC_S_FBUF32:
>>   	case VIDIOC_OVERLAY32:
>>   	case VIDIOC_QBUF32:
>> +	case VIDIOC_EXPBUF:
>>   	case VIDIOC_DQBUF32:
>>   	case VIDIOC_STREAMON32:
>>   	case VIDIOC_STREAMOFF32:
>> diff --git a/drivers/media/video/v4l2-ioctl.c b/drivers/media/video/v4l2-ioctl.c
>> index e1da8fc..cb29e00 100644
>> --- a/drivers/media/video/v4l2-ioctl.c
>> +++ b/drivers/media/video/v4l2-ioctl.c
>> @@ -207,6 +207,7 @@ static const char *v4l2_ioctls[] = {
>>   	[_IOC_NR(VIDIOC_S_FBUF)]           = "VIDIOC_S_FBUF",
>>   	[_IOC_NR(VIDIOC_OVERLAY)]          = "VIDIOC_OVERLAY",
>>   	[_IOC_NR(VIDIOC_QBUF)]             = "VIDIOC_QBUF",
>> +	[_IOC_NR(VIDIOC_EXPBUF)]           = "VIDIOC_EXPBUF",
>>   	[_IOC_NR(VIDIOC_DQBUF)]            = "VIDIOC_DQBUF",
>>   	[_IOC_NR(VIDIOC_STREAMON)]         = "VIDIOC_STREAMON",
>>   	[_IOC_NR(VIDIOC_STREAMOFF)]        = "VIDIOC_STREAMOFF",
>> @@ -932,6 +933,16 @@ static long __video_do_ioctl(struct file *file,
>>   			dbgbuf(cmd, vfd, p);
>>   		break;
>>   	}
>> +	case VIDIOC_EXPBUF:
>> +	{
>> +		unsigned int *p = arg;
>> +
>> +		if (!ops->vidioc_expbuf)
>> +			break;
>> +
>> +		ret = ops->vidioc_expbuf(file, fh, *p);
>> +		break;
>> +	}
>>   	case VIDIOC_DQBUF:
>>   	{
>>   		struct v4l2_buffer *p = arg;
>> diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
>> index 3c0ade1..448fbed 100644
>> --- a/include/linux/videodev2.h
>> +++ b/include/linux/videodev2.h
>> @@ -2183,6 +2183,7 @@ struct v4l2_create_buffers {
>>   #define VIDIOC_S_FBUF		 _IOW('V', 11, struct v4l2_framebuffer)
>>   #define VIDIOC_OVERLAY		 _IOW('V', 14, int)
>>   #define VIDIOC_QBUF		_IOWR('V', 15, struct v4l2_buffer)
>> +#define VIDIOC_EXPBUF		_IOWR('V', 16, __u32)
>>   #define VIDIOC_DQBUF		_IOWR('V', 17, struct v4l2_buffer)
>>   #define VIDIOC_STREAMON		 _IOW('V', 18, int)
>>   #define VIDIOC_STREAMOFF	 _IOW('V', 19, int)
>> diff --git a/include/media/v4l2-ioctl.h b/include/media/v4l2-ioctl.h
>> index 4d1c74a..8201546 100644
>> --- a/include/media/v4l2-ioctl.h
>> +++ b/include/media/v4l2-ioctl.h
>> @@ -120,6 +120,7 @@ struct v4l2_ioctl_ops {
>>   	int (*vidioc_reqbufs) (struct file *file, void *fh, struct v4l2_requestbuffers *b);
>>   	int (*vidioc_querybuf)(struct file *file, void *fh, struct v4l2_buffer *b);
>>   	int (*vidioc_qbuf)    (struct file *file, void *fh, struct v4l2_buffer *b);
>> +	int (*vidioc_expbuf)  (struct file *file, void *fh, __u32 offset);
>>   	int (*vidioc_dqbuf)   (struct file *file, void *fh, struct v4l2_buffer *b);
>>
>>   	int (*vidioc_create_bufs)(struct file *file, void *fh, struct v4l2_create_buffers *b);
>