[libcamera-devel] Fwd: Surface Go VCM type (was: Need to pass acpi_enforce_resources=lax on the Surface Go (version1))

[Hans de Goede]

Hi,

On 11/2/21 00:43, Daniel Scally wrote:
> Hi Hans

<snip>
 

>> 2. I need some help with all the fwnode link stuff (I'm not very familiar
>> with this). There seems to be a chicken and egg problem here though,
>> because the v4l2subdev for the VCM does not register because of async stuff
>> and if we add it to the "graph" then my idea to enumerate the VCMs
>> from the SSDB on the complete() callback won't work. But we can do this
>> on a per sensor basis instead from the cio2_notifier_bound() callback
>> instead I guess ?
> 
> 
> I think on top of your work in the cio2-bridge for patch 3 you can do this:
> 
> 
> 1. Create another software node against the cio2_sensor struct, with the
> name coming from the vcm_types array
> 
> 2. Assign that software node to board_info.swnode in
> cio2_bridge_instantiate_vcm_i2c_client()
> 
> 3. Add another entry to dev_properties for the sensor, that is named
> "lens-focus" and contains a reference to the software_node created in #2
> just like the references to the sensor/cio2 nodes.
> 
> 
> This way when the sensor driver calls
> v4l2_async_register_subdev_sensor() it should create a notifier that
> looks for that VCM client to bind. I think then rather than putting
> anything in the .bound() / .complete() callbacks, we should modify core
> to do _something_ when async matching some subdevs. The something would
> depend on the kind of devices that match, for example with the sensor
> driver and the ipu3-cio2 driver, there's an entity whos function is
> MEDIA_ENT_F_VID_IF_BRIDGE matching to an entity whos function is
> MEDIA_ENT_F_CAM_SENSOR, and it seems to me that every scenario like that
> is going to result in media pad links being created. Similarly for our
> sensor that's a device with entity function MEDIA_ENT_F_LENS matching to
> MEDIA_ENT_F_CAM_SENSOR, and I think that in those cases we can create
> either an interface link or a new kind of link (maybe
> "MEDIA_LNK_FL_ANCILLARY_LINK" or something...) between the two to show
> that they form a single logical unit, which we can then report to libcamera.
> 
> 
> Hope that makes sense...

Ok, so I gave this a try, see the attached patches, but the v4l2-subdev for
the VCM still does not show up.

I think that instead I need to build a full link between the sensor
and the VCM similar to the cio2 <-> sensor link. Both ends of that link
have:

<base-swnode attached to the device>
|
--<port-swnode named (SWNODE_GRAPH_PORT_NAME_FMT, X), where X is 0 on the
  |                           sensor side and the link nr on the cio2 side
  |
  --<end-point-swnode named (SWNODE_GRAPH_ENDPOINT_NAME_FMT, 0)

And then the 2 endpoints contain a swref property pointing to the
other endpoint swnode.

I think we need a similar setup adding a swnode child named
(SWNODE_GRAPH_PORT_NAME_FMT, 1), to the nodes[SWNODE_SENSOR_HID] node.

Note 1, since 0 is the "port" to the cio2, this new port child then
gets an endpoint "0" child itself, likewise we add a "port 0" child
to the vcm swnode, with a "endpoint 0" child below that and then have
the 2 endpoints contain swref properties pointing to each other.

I think that this will properly make the VCm part of the graph and
will make its v4l2-subdev get instantiated when the graph is
complete.  Before I spend a bunch of time on implementing this,
let me ask this:

Does this sound reasonable / like I'm heading in the right direction?

Regards,

Hans



p.s.

I have found a new solution for the probe-ordering problem which
is patch 2 of the attached patches, I personally I'm happy with
this solution. I hope you like it too.
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