[libcamera-devel] [PATCH 2/2] libcamera: v4l2_videodevice: Print fd value in log prefix

[Laurent Pinchart]

Hi Kieran,

On Wed, Mar 03, 2021 at 04:41:47PM +0000, Kieran Bingham wrote:
> On 03/03/2021 16:37, Laurent Pinchart wrote:
> > When opening a V4L2VideoDevice multiple times, for instance to run
> > multiple jobs on a M2M device, it's useful to attribute log messages to
> > a particular instance. Include the device fd in the log prefix.
> 
> An example of how the change looks in the output might have been nice here.
> 
> It looks like it goes from
> 
> [out] or [cap]
>  to
> [234:out] or [234:cap]

Good point. I'll add

This turns the existing output

[1:43:01.958321522] [277] DEBUG V4L2 v4l2_videodevice.cpp:1440 /dev/video0[cap]: Queueing buffer 0
[1:43:01.958350060] [277] DEBUG V4L2 v4l2_videodevice.cpp:1440 /dev/video0[cap]: Queueing buffer 1
[1:43:01.958365137] [277] DEBUG V4L2 v4l2_videodevice.cpp:1440 /dev/video0[cap]: Queueing buffer 2

into

[1:43:01.958321522] [277] DEBUG V4L2 v4l2_videodevice.cpp:1440 /dev/video0[14:cap]: Queueing buffer 0
[1:43:01.958350060] [277] DEBUG V4L2 v4l2_videodevice.cpp:1440 /dev/video0[14:cap]: Queueing buffer 1
[1:43:01.958365137] [277] DEBUG V4L2 v4l2_videodevice.cpp:1440 /dev/video0[14:cap]: Queueing buffer 2

> Which is fine by me, and gives each context a unique reference.
> 
> We could choose to do that only on M2M nodes if those are the only ones
> that are possible to open multiple times ... but maybe that's overkill
> and would require more processing in this code path.

That, and it may make it more difficult for scripts to process the log,
if needed.

> Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> 
> > Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> > ---
> >  src/libcamera/v4l2_videodevice.cpp | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
> > index c77e1aff7978..cb52d4cea3f6 100644
> > --- a/src/libcamera/v4l2_videodevice.cpp
> > +++ b/src/libcamera/v4l2_videodevice.cpp
> > @@ -711,7 +711,8 @@ void V4L2VideoDevice::close()
> >  
> >  std::string V4L2VideoDevice::logPrefix() const
> >  {
> > -	return deviceNode() + (V4L2_TYPE_IS_OUTPUT(bufferType_) ? "[out]" : "[cap]");
> > +	return deviceNode() + "[" + std::to_string(fd()) +
> > +		(V4L2_TYPE_IS_OUTPUT(bufferType_) ? ":out]" : ":cap]");
> >  }
> >  
> >  /**

-- 
Regards,

Laurent Pinchart