[libcamera-devel,v3] libcamera: device_enumerator: ensure deviceNode is not empty
diff mbox series

Message ID 20230609-empty-devnode-v3-1-c08f450ba062@skidata.com
State Accepted
Commit 90fa9a0f2b6dc209e22950a871a79343661e1d09
Headers show
Series
  • [libcamera-devel,v3] libcamera: device_enumerator: ensure deviceNode is not empty
Related show

Commit Message

Benjamin Bara July 6, 2023, 11:41 a.m. UTC 
From: Benjamin Bara <benjamin.bara@skidata.com>

When activating both ISP nodes on the i.MX8MP, but only connecting one
camera sensor, libcamera aborts because it couldn't find the chosen
entity's device node:

[37:54:40.779902250] [3631] DEBUG DeviceEnumerator device_enumerator.cpp:252 Added device /dev/media1: rkisp1
[37:54:40.780196750] [3631] DEBUG DeviceEnumerator device_enumerator_udev.cpp:322 All dependencies for media device /dev/media0 found
[37:54:40.780237875] [3631] DEBUG DeviceEnumerator device_enumerator.cpp:252 Added device /dev/media0: rkisp1
[37:54:40.780505125] [3631] DEBUG Camera camera_manager.cpp:152 Found registered pipeline handler 'PipelineHandlerRkISP1'
[37:54:40.780599875] [3631] DEBUG DeviceEnumerator device_enumerator.cpp:312 Successful match for media device "rkisp1"
[37:54:40.780731375] [3631] ERROR V4L2 v4l2_device.cpp:93 'rkisp1_isp': Failed to open V4L2 device '': No such file or directory

Fix this by skipping empty device nodes:

[37:49:05.172672000] [3603] DEBUG DeviceEnumerator device_enumerator_udev.cpp:322 All dependencies for media device /dev/media1 found
[37:49:05.172720625] [3603] DEBUG DeviceEnumerator device_enumerator.cpp:256 Added device /dev/media1: rkisp1
[37:49:05.172973875] [3603] DEBUG DeviceEnumerator device_enumerator_udev.cpp:322 All dependencies for media device /dev/media0 found
[37:49:05.173012125] [3603] DEBUG DeviceEnumerator device_enumerator.cpp:256 Added device /dev/media0: rkisp1
[37:49:05.173281625] [3603] DEBUG Camera camera_manager.cpp:152 Found registered pipeline handler 'PipelineHandlerRkISP1'
[37:49:05.173376875] [3603] DEBUG DeviceEnumerator device_enumerator.cpp:107 Skip rkisp1_isp: no device node
[37:49:05.173414375] [3603] DEBUG DeviceEnumerator device_enumerator.cpp:316 Successful match for media device "rkisp1"
[37:49:05.173671250] [3603] DEBUG V4L2 v4l2_videodevice.cpp:632 /dev/video1[15:cap]: Opened device platform:rkisp1: rkisp1: rkisp1_stats
[37:49:05.173775125] [3603] DEBUG V4L2 v4l2_videodevice.cpp:632 /dev/video2[16:out]: Opened device platform:rkisp1: rkisp1: rkisp1_params
[37:49:05.173880500] [3603] DEBUG V4L2 v4l2_videodevice.cpp:632 /dev/video0[18:cap]: Opened device platform:rkisp1: rkisp1: rkisp1

Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Benjamin Bara <benjamin.bara@skidata.com>
---
Hi!

The dots look like this:

/dev/media0:
digraph board {
        rankdir=TB
        n00000001 [label="{{<port0> 0 | <port1> 1} | rkisp1_isp\n | {<port2> 2 | <port3> 3}}", shape=Mrecord, style=filled, fillcolor=green]
        n00000001:port2 -> n00000006:port0
        n00000001:port3 -> n0000000d [style=bold]
        n00000006 [label="{{<port0> 0} | rkisp1_resizer_mainpath\n | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
        n00000006:port1 -> n00000009 [style=bold]
        n00000009 [label="rkisp1_mainpath\n/dev/video0", shape=box, style=filled, fillcolor=yellow]
        n0000000d [label="rkisp1_stats\n/dev/video1", shape=box, style=filled, fillcolor=yellow]
        n00000011 [label="rkisp1_params\n/dev/video2", shape=box, style=filled, fillcolor=yellow]
        n00000011 -> n00000001:port1 [style=bold]
        n0000001d [label="{{<port0> 0} | csis-32e40000.csi\n | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
        n0000001d:port1 -> n00000001:port0
}

/dev/media1:
digraph board {
        rankdir=TB
        n00000001 [label="{{<port0> 0 | <port1> 1} | rkisp1_isp\n/dev/v4l-subdev0 | {<port2> 2 | <port3> 3}}", shape=Mrecord, style=filled, fillcolor=green]
        n00000001:port2 -> n00000006:port0
        n00000001:port3 -> n0000000d [style=bold]
        n00000006 [label="{{<port0> 0} | rkisp1_resizer_mainpath\n/dev/v4l-subdev1 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
        n00000006:port1 -> n00000009 [style=bold]
        n00000009 [label="rkisp1_mainpath\n/dev/video3", shape=box, style=filled, fillcolor=yellow]
        n0000000d [label="rkisp1_stats\n/dev/video4", shape=box, style=filled, fillcolor=yellow]
        n00000011 [label="rkisp1_params\n/dev/video5", shape=box, style=filled, fillcolor=yellow]
        n00000011 -> n00000001:port1 [style=bold]
        n0000001d [label="{{<port0> 0} | csis-32e50000.csi\n/dev/v4l-subdev2 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
        n0000001d:port1 -> n00000001:port0
        n00000022 [label="{{} | imx327 8-001a\n/dev/v4l-subdev3 | {<port0> 0}}", shape=Mrecord, style=filled, fillcolor=green]
        n00000022:port0 -> n0000001d:port0
}
---
Changes in v3:
- adapt check (thx to Kieran)
- Link to v2: https://lists.libcamera.org/pipermail/libcamera-devel/2023-June/038182.html

Changes in v2:
- adapt commit message
- Link to v1: https://lists.libcamera.org/pipermail/libcamera-devel/2023-June/038181.html
---
 src/libcamera/device_enumerator.cpp | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)


---
base-commit: 0ee9339331c648232e87d2de2ccd5a92cc61cab2
change-id: 20230609-empty-devnode-36dd2647cde0

Best regards,

Comments

Laurent Pinchart July 6, 2023, 3:53 p.m. UTC | #1 
Hi Benjamin,

Thank you for the patch.

On Thu, Jul 06, 2023 at 01:41:11PM +0200, Benjamin Bara via libcamera-devel wrote:
> From: Benjamin Bara <benjamin.bara@skidata.com>
> 
> When activating both ISP nodes on the i.MX8MP, but only connecting one
> camera sensor, libcamera aborts because it couldn't find the chosen
> entity's device node:

Why is this ? I assume that's because the kernel driver only registers
subdevs once connected sensors have been found, given that video nodes
are there. It would be nice to record that in the commit message.

> [37:54:40.779902250] [3631] DEBUG DeviceEnumerator device_enumerator.cpp:252 Added device /dev/media1: rkisp1
> [37:54:40.780196750] [3631] DEBUG DeviceEnumerator device_enumerator_udev.cpp:322 All dependencies for media device /dev/media0 found
> [37:54:40.780237875] [3631] DEBUG DeviceEnumerator device_enumerator.cpp:252 Added device /dev/media0: rkisp1
> [37:54:40.780505125] [3631] DEBUG Camera camera_manager.cpp:152 Found registered pipeline handler 'PipelineHandlerRkISP1'
> [37:54:40.780599875] [3631] DEBUG DeviceEnumerator device_enumerator.cpp:312 Successful match for media device "rkisp1"
> [37:54:40.780731375] [3631] ERROR V4L2 v4l2_device.cpp:93 'rkisp1_isp': Failed to open V4L2 device '': No such file or directory
> 
> Fix this by skipping empty device nodes:
> 
> [37:49:05.172672000] [3603] DEBUG DeviceEnumerator device_enumerator_udev.cpp:322 All dependencies for media device /dev/media1 found
> [37:49:05.172720625] [3603] DEBUG DeviceEnumerator device_enumerator.cpp:256 Added device /dev/media1: rkisp1
> [37:49:05.172973875] [3603] DEBUG DeviceEnumerator device_enumerator_udev.cpp:322 All dependencies for media device /dev/media0 found
> [37:49:05.173012125] [3603] DEBUG DeviceEnumerator device_enumerator.cpp:256 Added device /dev/media0: rkisp1
> [37:49:05.173281625] [3603] DEBUG Camera camera_manager.cpp:152 Found registered pipeline handler 'PipelineHandlerRkISP1'
> [37:49:05.173376875] [3603] DEBUG DeviceEnumerator device_enumerator.cpp:107 Skip rkisp1_isp: no device node
> [37:49:05.173414375] [3603] DEBUG DeviceEnumerator device_enumerator.cpp:316 Successful match for media device "rkisp1"
> [37:49:05.173671250] [3603] DEBUG V4L2 v4l2_videodevice.cpp:632 /dev/video1[15:cap]: Opened device platform:rkisp1: rkisp1: rkisp1_stats
> [37:49:05.173775125] [3603] DEBUG V4L2 v4l2_videodevice.cpp:632 /dev/video2[16:out]: Opened device platform:rkisp1: rkisp1: rkisp1_params
> [37:49:05.173880500] [3603] DEBUG V4L2 v4l2_videodevice.cpp:632 /dev/video0[18:cap]: Opened device platform:rkisp1: rkisp1: rkisp1
> 
> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> Signed-off-by: Benjamin Bara <benjamin.bara@skidata.com>
> ---
> Hi!
> 
> The dots look like this:
> 
> /dev/media0:
> digraph board {
>         rankdir=TB
>         n00000001 [label="{{<port0> 0 | <port1> 1} | rkisp1_isp\n | {<port2> 2 | <port3> 3}}", shape=Mrecord, style=filled, fillcolor=green]
>         n00000001:port2 -> n00000006:port0
>         n00000001:port3 -> n0000000d [style=bold]
>         n00000006 [label="{{<port0> 0} | rkisp1_resizer_mainpath\n | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
>         n00000006:port1 -> n00000009 [style=bold]
>         n00000009 [label="rkisp1_mainpath\n/dev/video0", shape=box, style=filled, fillcolor=yellow]
>         n0000000d [label="rkisp1_stats\n/dev/video1", shape=box, style=filled, fillcolor=yellow]
>         n00000011 [label="rkisp1_params\n/dev/video2", shape=box, style=filled, fillcolor=yellow]
>         n00000011 -> n00000001:port1 [style=bold]
>         n0000001d [label="{{<port0> 0} | csis-32e40000.csi\n | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
>         n0000001d:port1 -> n00000001:port0
> }
> 
> /dev/media1:
> digraph board {
>         rankdir=TB
>         n00000001 [label="{{<port0> 0 | <port1> 1} | rkisp1_isp\n/dev/v4l-subdev0 | {<port2> 2 | <port3> 3}}", shape=Mrecord, style=filled, fillcolor=green]
>         n00000001:port2 -> n00000006:port0
>         n00000001:port3 -> n0000000d [style=bold]
>         n00000006 [label="{{<port0> 0} | rkisp1_resizer_mainpath\n/dev/v4l-subdev1 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
>         n00000006:port1 -> n00000009 [style=bold]
>         n00000009 [label="rkisp1_mainpath\n/dev/video3", shape=box, style=filled, fillcolor=yellow]
>         n0000000d [label="rkisp1_stats\n/dev/video4", shape=box, style=filled, fillcolor=yellow]
>         n00000011 [label="rkisp1_params\n/dev/video5", shape=box, style=filled, fillcolor=yellow]
>         n00000011 -> n00000001:port1 [style=bold]
>         n0000001d [label="{{<port0> 0} | csis-32e50000.csi\n/dev/v4l-subdev2 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
>         n0000001d:port1 -> n00000001:port0
>         n00000022 [label="{{} | imx327 8-001a\n/dev/v4l-subdev3 | {<port0> 0}}", shape=Mrecord, style=filled, fillcolor=green]
>         n00000022:port0 -> n0000001d:port0
> }
> ---
> Changes in v3:
> - adapt check (thx to Kieran)
> - Link to v2: https://lists.libcamera.org/pipermail/libcamera-devel/2023-June/038182.html
> 
> Changes in v2:
> - adapt commit message
> - Link to v1: https://lists.libcamera.org/pipermail/libcamera-devel/2023-June/038181.html
> ---
>  src/libcamera/device_enumerator.cpp | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/src/libcamera/device_enumerator.cpp b/src/libcamera/device_enumerator.cpp
> index f2e055de..42b5ba6c 100644
> --- a/src/libcamera/device_enumerator.cpp
> +++ b/src/libcamera/device_enumerator.cpp
> @@ -101,8 +101,14 @@ bool DeviceMatch::match(const MediaDevice *device) const
>  
>  		for (const MediaEntity *entity : device->entities()) {
>  			if (name == entity->name()) {
> -				found = true;
> -				break;
> +				if (!entity->deviceNode().empty()) {
> +					found = true;
> +					break;
> +				} else {
> +					LOG(DeviceEnumerator, Debug)
> +						<< "Skip " << entity->name()
> +						<< ": no device node";
> +				}
>  			}
>  		}

Should we break when the device node list is empty ? We can't have two
entities in the graph with the same name. Something along the lines of

		for (const MediaEntity *entity : device->entities()) {
			if (name == entity->name()) {
				if (entity->deviceNode().empty())
					LOG(DeviceEnumerator, Debug)
						<< "Skip " << entity->name()
						<< ": no device node";
				else
					found = true;
				break;
			}
		}

or

		for (const MediaEntity *entity : device->entities()) {
			if (name != entity->name())
				continue;

			if (entity->deviceNode().empty())
				LOG(DeviceEnumerator, Debug)
					<< "Skip " << entity->name()
					<< ": no device node";
			else
				found = true;
			break;
		}

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

>  
> 
> ---
> base-commit: 0ee9339331c648232e87d2de2ccd5a92cc61cab2
> change-id: 20230609-empty-devnode-36dd2647cde0
Kieran Bingham July 11, 2023, 1:45 p.m. UTC | #2 
Quoting Laurent Pinchart via libcamera-devel (2023-07-06 16:53:44)
> Hi Benjamin,
> 
> Thank you for the patch.
> 
> On Thu, Jul 06, 2023 at 01:41:11PM +0200, Benjamin Bara via libcamera-devel wrote:
> > From: Benjamin Bara <benjamin.bara@skidata.com>
> > 
> > When activating both ISP nodes on the i.MX8MP, but only connecting one
> > camera sensor, libcamera aborts because it couldn't find the chosen
> > entity's device node:
> 
> Why is this ? I assume that's because the kernel driver only registers
> subdevs once connected sensors have been found, given that video nodes
> are there. It would be nice to record that in the commit message.
> 
> > [37:54:40.779902250] [3631] DEBUG DeviceEnumerator device_enumerator.cpp:252 Added device /dev/media1: rkisp1
> > [37:54:40.780196750] [3631] DEBUG DeviceEnumerator device_enumerator_udev.cpp:322 All dependencies for media device /dev/media0 found
> > [37:54:40.780237875] [3631] DEBUG DeviceEnumerator device_enumerator.cpp:252 Added device /dev/media0: rkisp1
> > [37:54:40.780505125] [3631] DEBUG Camera camera_manager.cpp:152 Found registered pipeline handler 'PipelineHandlerRkISP1'
> > [37:54:40.780599875] [3631] DEBUG DeviceEnumerator device_enumerator.cpp:312 Successful match for media device "rkisp1"
> > [37:54:40.780731375] [3631] ERROR V4L2 v4l2_device.cpp:93 'rkisp1_isp': Failed to open V4L2 device '': No such file or directory
> > 
> > Fix this by skipping empty device nodes:
> > 
> > [37:49:05.172672000] [3603] DEBUG DeviceEnumerator device_enumerator_udev.cpp:322 All dependencies for media device /dev/media1 found
> > [37:49:05.172720625] [3603] DEBUG DeviceEnumerator device_enumerator.cpp:256 Added device /dev/media1: rkisp1
> > [37:49:05.172973875] [3603] DEBUG DeviceEnumerator device_enumerator_udev.cpp:322 All dependencies for media device /dev/media0 found
> > [37:49:05.173012125] [3603] DEBUG DeviceEnumerator device_enumerator.cpp:256 Added device /dev/media0: rkisp1
> > [37:49:05.173281625] [3603] DEBUG Camera camera_manager.cpp:152 Found registered pipeline handler 'PipelineHandlerRkISP1'
> > [37:49:05.173376875] [3603] DEBUG DeviceEnumerator device_enumerator.cpp:107 Skip rkisp1_isp: no device node
> > [37:49:05.173414375] [3603] DEBUG DeviceEnumerator device_enumerator.cpp:316 Successful match for media device "rkisp1"
> > [37:49:05.173671250] [3603] DEBUG V4L2 v4l2_videodevice.cpp:632 /dev/video1[15:cap]: Opened device platform:rkisp1: rkisp1: rkisp1_stats
> > [37:49:05.173775125] [3603] DEBUG V4L2 v4l2_videodevice.cpp:632 /dev/video2[16:out]: Opened device platform:rkisp1: rkisp1: rkisp1_params
> > [37:49:05.173880500] [3603] DEBUG V4L2 v4l2_videodevice.cpp:632 /dev/video0[18:cap]: Opened device platform:rkisp1: rkisp1: rkisp1
> > 
> > Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> > Signed-off-by: Benjamin Bara <benjamin.bara@skidata.com>
> > ---
> > Hi!
> > 
> > The dots look like this:
> > 
> > /dev/media0:
> > digraph board {
> >         rankdir=TB
> >         n00000001 [label="{{<port0> 0 | <port1> 1} | rkisp1_isp\n | {<port2> 2 | <port3> 3}}", shape=Mrecord, style=filled, fillcolor=green]
> >         n00000001:port2 -> n00000006:port0
> >         n00000001:port3 -> n0000000d [style=bold]
> >         n00000006 [label="{{<port0> 0} | rkisp1_resizer_mainpath\n | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
> >         n00000006:port1 -> n00000009 [style=bold]
> >         n00000009 [label="rkisp1_mainpath\n/dev/video0", shape=box, style=filled, fillcolor=yellow]
> >         n0000000d [label="rkisp1_stats\n/dev/video1", shape=box, style=filled, fillcolor=yellow]
> >         n00000011 [label="rkisp1_params\n/dev/video2", shape=box, style=filled, fillcolor=yellow]
> >         n00000011 -> n00000001:port1 [style=bold]
> >         n0000001d [label="{{<port0> 0} | csis-32e40000.csi\n | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
> >         n0000001d:port1 -> n00000001:port0
> > }
> > 
> > /dev/media1:
> > digraph board {
> >         rankdir=TB
> >         n00000001 [label="{{<port0> 0 | <port1> 1} | rkisp1_isp\n/dev/v4l-subdev0 | {<port2> 2 | <port3> 3}}", shape=Mrecord, style=filled, fillcolor=green]
> >         n00000001:port2 -> n00000006:port0
> >         n00000001:port3 -> n0000000d [style=bold]
> >         n00000006 [label="{{<port0> 0} | rkisp1_resizer_mainpath\n/dev/v4l-subdev1 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
> >         n00000006:port1 -> n00000009 [style=bold]
> >         n00000009 [label="rkisp1_mainpath\n/dev/video3", shape=box, style=filled, fillcolor=yellow]
> >         n0000000d [label="rkisp1_stats\n/dev/video4", shape=box, style=filled, fillcolor=yellow]
> >         n00000011 [label="rkisp1_params\n/dev/video5", shape=box, style=filled, fillcolor=yellow]
> >         n00000011 -> n00000001:port1 [style=bold]
> >         n0000001d [label="{{<port0> 0} | csis-32e50000.csi\n/dev/v4l-subdev2 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
> >         n0000001d:port1 -> n00000001:port0
> >         n00000022 [label="{{} | imx327 8-001a\n/dev/v4l-subdev3 | {<port0> 0}}", shape=Mrecord, style=filled, fillcolor=green]
> >         n00000022:port0 -> n0000001d:port0
> > }

Thanks - that's helpful to see what was going on.


> > ---
> > Changes in v3:
> > - adapt check (thx to Kieran)
> > - Link to v2: https://lists.libcamera.org/pipermail/libcamera-devel/2023-June/038182.html
> > 
> > Changes in v2:
> > - adapt commit message
> > - Link to v1: https://lists.libcamera.org/pipermail/libcamera-devel/2023-June/038181.html
> > ---
> >  src/libcamera/device_enumerator.cpp | 10 ++++++++--
> >  1 file changed, 8 insertions(+), 2 deletions(-)
> > 
> > diff --git a/src/libcamera/device_enumerator.cpp b/src/libcamera/device_enumerator.cpp
> > index f2e055de..42b5ba6c 100644
> > --- a/src/libcamera/device_enumerator.cpp
> > +++ b/src/libcamera/device_enumerator.cpp
> > @@ -101,8 +101,14 @@ bool DeviceMatch::match(const MediaDevice *device) const
> >  
> >               for (const MediaEntity *entity : device->entities()) {
> >                       if (name == entity->name()) {
> > -                             found = true;
> > -                             break;
> > +                             if (!entity->deviceNode().empty()) {
> > +                                     found = true;
> > +                                     break;
> > +                             } else {
> > +                                     LOG(DeviceEnumerator, Debug)
> > +                                             << "Skip " << entity->name()
> > +                                             << ": no device node";
> > +                             }
> >                       }
> >               }
> 
> Should we break when the device node list is empty ? We can't have two
> entities in the graph with the same name. Something along the lines of
> 
>                 for (const MediaEntity *entity : device->entities()) {
>                         if (name == entity->name()) {
>                                 if (entity->deviceNode().empty())
>                                         LOG(DeviceEnumerator, Debug)
>                                                 << "Skip " << entity->name()
>                                                 << ": no device node";
>                                 else
>                                         found = true;
>                                 break;
>                         }
>                 }
> 
> or
> 
>                 for (const MediaEntity *entity : device->entities()) {
>                         if (name != entity->name())
>                                 continue;
> 
>                         if (entity->deviceNode().empty())
>                                 LOG(DeviceEnumerator, Debug)
>                                         << "Skip " << entity->name()
>                                         << ": no device node";
>                         else
>                                 found = true;
>                         break;
>                 }
> 

Benjamin,

The second option here looks better to me overall. Do you have a
preference? I can update the patch while applying - no need to send a
new patch - but the final choice is yours as it's your patch.

As this fixes a user facing issue - I'd like to get this in soon so it's
included in the next release.

--
Kieran


> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> 
> >  
> > 
> > ---
> > base-commit: 0ee9339331c648232e87d2de2ccd5a92cc61cab2
> > change-id: 20230609-empty-devnode-36dd2647cde0
> 
> -- 
> Regards,
> 
> Laurent Pinchart

Patch
diff mbox series 

diff --git a/src/libcamera/device_enumerator.cpp b/src/libcamera/device_enumerator.cpp
index f2e055de..42b5ba6c 100644
--- a/src/libcamera/device_enumerator.cpp
+++ b/src/libcamera/device_enumerator.cpp
@@ -101,8 +101,14 @@  bool DeviceMatch::match(const MediaDevice *device) const
 
 		for (const MediaEntity *entity : device->entities()) {
 			if (name == entity->name()) {
-				found = true;
-				break;
+				if (!entity->deviceNode().empty()) {
+					found = true;
+					break;
+				} else {
+					LOG(DeviceEnumerator, Debug)
+						<< "Skip " << entity->name()
+						<< ": no device node";
+				}
 			}
 		}