drm: Stable identification of connectors?

[Albert, Joerg (TT-U)]

Hi,


I’m pretty new to DRM/DRI and wonder if there is a way to have a stable identification of connectors across changes in the Linux kernel and/or in the devicetree?

Our hardware contains an iMX8QM with two displays, each one connected to a MIPI-DSI channel. We use kernel 6.1.38.
In the output of “modetest -c” the connectors are called LVDS-1 and LVDS-2. These names are built in modetest.c from connector_type and connector_type_id.

connector_type_id is set in the kernel in drivers/gpu/drm/drm_connector.c in __drm_connector_init():


       connector<https://elixir.bootlin.com/linux/latest/C/ident/connector>->connector_type_id<https://elixir.bootlin.com/linux/latest/C/ident/connector_type_id> =

              ida_alloc_min<https://elixir.bootlin.com/linux/latest/C/ident/ida_alloc_min>(connector_ida<https://elixir.bootlin.com/linux/latest/C/ident/connector_ida>, 1, GFP_KERNEL<https://elixir.bootlin.com/linux/latest/C/ident/GFP_KERNEL>);

Seems to me that this number depends on initialization order only. Is there any other way to identify a connector?

If not, will the type_id be stable as long as we don’t change the kernel version and the device tree?


Best Regards,
Joerg Albert






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