Re: [PATCH 1/1 v3] libv4l: Add plugin support to libv4l

[Yordan Kamenov <ykamenov@mm-sol.com>]

Hans de Goede wrote:
> Hi,
>
Hi Hans,

Thanks for your comments.
> First of all my apologies for taking so long to get around to
> reviewing this.
>
> Over all it looks good, I've put some small remarks inline, if
> you fix these I can merge this. I wonder though, given the recent
> limbo around Nokia's change of focus, if there are any plans to
> actually move forward with a plugin using this... ?
>
> The reason I'm asking is that adding the plugin framework if nothing
> is going to use it seems a bit senseless.
We are working on a "media controller" plugin which allows
a traditional v4l2 application to work with Media Controller
framework. The idea is when the application opens /dev/video0, then
the plugin initializes media controller and creates appropriate pipeline,
after that the plugin redirects all ioctl's from the application to this
pipeline and on close call the pipeline is deinitialized.
>
> Regards,
>
> Hans
>
>
> On 02/14/2011 12:02 PM, Yordan Kamenov wrote: 
[snip]
>
>> diff --git a/lib/libv4l2/v4l2convert.c b/lib/libv4l2/v4l2convert.c
>> index e251085..03f34ad 100644
>> --- a/lib/libv4l2/v4l2convert.c
>> +++ b/lib/libv4l2/v4l2convert.c
>> @@ -46,7 +46,6 @@
>>   LIBV4L_PUBLIC int open(const char *file, int oflag, ...)
>>   {
>>       int fd;
>> -    struct v4l2_capability cap;
>>       int v4l_device = 0;
>>
>>       /* check if we're opening a video4linux2 device */
>> @@ -76,14 +75,6 @@ LIBV4L_PUBLIC int open(const char *file, int 
>> oflag, ...)
>>       if (fd == -1 || !v4l_device)
>>           return fd;
>>
>> -    /* check that this is an v4l2 device, libv4l2 only supports v4l2 
>> devices */
>> -    if (SYS_IOCTL(fd, VIDIOC_QUERYCAP,&cap))
>> -        return fd;
>> -
>> -    /* libv4l2 only adds functionality to capture capable devices */
>> -    if (!(cap.capabilities&  V4L2_CAP_VIDEO_CAPTURE))
>> -        return fd;
>> -
>>       /* Try to Register with libv4l2 (in case of failure pass the fd 
>> to the
>>          application as is) */
>>       v4l2_fd_open(fd, 0);
>
> Hmm, why are you removing this check ?
>
In case of above example of media controller plugin when the application 
opens
/dev/video0, then this plugin should be used. But in media controller 
framework
/dev/video0 file might correspond to a subdevice which is not a capture 
device and
this fd will not be registered in libv4l2 at all.

Regards
Yordan