[libcamera-devel] [PATCH 0/3] libcamera: Add new Camera devices property

[Kieran Bingham]

Hi Jacopo

On 19/04/2023 10:45, Jacopo Mondi wrote:
> Hi Kieran
> 
> On Wed, Apr 19, 2023 at 09:58:18AM +0100, Kieran Bingham via libcamera-devel wrote:
>> It can be beneficial to allow reporting the devices used by a camera to
>> facilitate de-duplication of resources when handling cameras from a
>> centralised infrastructure such as PipeWire.
>>
> 
> This series allows to retrieve the list of dev_t a libcamera::Camera
> handles by using a camera properties.
> 
> The CameraManager class however maintains a camerasByDevnum_ map that
> associates a dev_t with the Camera it is owned by. It would be trivial
> to reverse the map. Have you considered that ? Getting dev_t from the
> manager seems more natural than doing so from the Camera (and would
> avoid the additional template specialization for dev_t you don't like)

No I haven't, so that's an interesting point. I'll take a look.

Robert/Wim,

Do you have any specific requirements here? Do you need to be able to 
map which devices are used by each camera? Or is a single list sufficient?

Or maybe returning a map of camera (id?) to device list is best all round?

My only thought on the separation is the list would have to be 
re-obtained for hotplugged cameras, while it's available at the 'camera' 
when on the object. Conversely, perhaps hotplug is a reason to 
centralize the whole list as after a camera is removed it would need to 
be updated anyway.

So - I'll see if I can add in a call on the Camera Manager that returns 
a map of camera id / dev_t.


--
Kieran