Re: [Discussion] Global vs Local devicetree overlays for addon board + connector setups

[Ayush Singh]

> It depends on the bus the device is added.
> when an overlay is applied by the kernel, OF_RECONFIG_* events are
> triggered. Some buses handle them:
>
> 	$ git grep OF_RECONFIG_CHANGE
> 	drivers/bus/imx-weim.c: case OF_RECONFIG_CHANGE_ADD:
> 	drivers/bus/imx-weim.c: case OF_RECONFIG_CHANGE_REMOVE:
> 	drivers/gpio/gpiolib-of.c:      case OF_RECONFIG_CHANGE_ADD:
> 	drivers/gpio/gpiolib-of.c:      case OF_RECONFIG_CHANGE_REMOVE:
> 	drivers/i2c/i2c-core-of.c:      case OF_RECONFIG_CHANGE_ADD:
> 	drivers/i2c/i2c-core-of.c:      case OF_RECONFIG_CHANGE_REMOVE:
> 	drivers/of/dynamic.c: * Return: OF_RECONFIG_CHANGE_REMOVE on device going from enabled to
> 	drivers/of/dynamic.c: * disabled, OF_RECONFIG_CHANGE_ADD on device going from disabled to
> 	drivers/of/dynamic.c:   return new_state ? OF_RECONFIG_CHANGE_ADD : OF_RECONFIG_CHANGE_REMOVE;
> 	drivers/of/platform.c:  case OF_RECONFIG_CHANGE_ADD:
> 	drivers/of/platform.c:  case OF_RECONFIG_CHANGE_REMOVE:
> 	drivers/spi/spi.c:      case OF_RECONFIG_CHANGE_ADD:
> 	drivers/spi/spi.c:      case OF_RECONFIG_CHANGE_REMOVE:
> 	include/linux/of.h:     OF_RECONFIG_CHANGE_ADD,
> 	include/linux/of.h:     OF_RECONFIG_CHANGE_REMOVE,


Well, if some bus does handle the event, I guess it is a bug in the 
subsystems that do not? Maybe Greg Kroah-Hartman can clarify the 
expected behavior here? Maybe we are in transition phase here.


Also I guess, feel free to suggest anyone else I should add to this 
discussion thread. I want everyone to come to an understanding regarding 
the fundamental behavior. I have been getting mixed signals in the 
various discussions I have had till now.


Ayush Singh