Generic Platform Discovery

New controller or hub components often need to add platforms in sub-components (i.e. Lights & Switches) without additional configuration. This can be achieved using the load_platform or async_load_platform methods from homeassistant.helpers.discovery:

def load_platform(hass, component, platform, discovered=None, hass_config=None)

From more info on how this works, refer to the load_platform method.

Example

Say you need to implement your new MyFlashyHub that controls both Switches & Lights, you can follow these steps:

Configuration required for your new hub component:

myflashyhub:
   example: setting

The source for your component can be located in your configuration directory for now:

~/.homeassistant/custom_components/myflashyhub.py
~/.homeassistant/custom_components/light/myflashyhub.py
~/.homeassistant/custom_components/switch/myflashyhub.py

In the hub component myflashyhub.py you can call your light and switch components. To pass any non-serializable information to the platforms in the sub-component, you can use a global variable.

from homeassistant.helpers.discovery import load_platform
DOMAIN = 'myflashyhub'

DATA_MFH = 'MFH'

def setup(hass, config):
    """Your controller/hub specific code."""
    hass.data[DATA_MFH] = SomeObjectToInitialiseGlobal()

    #--- snip ---
    load_platform(hass, 'light', DOMAIN)
    load_platform(hass, 'switch', DOMAIN, {'optional': 'arguments'})

Add your custom device specific code to the setup_platform method in light/myflashyhub.py and switch/myflashyhub.

import custom_components.myflashyhub as myflashyhub

# 'switch' will receive discovery_info={'optional': 'arguments'} 
# as passed in above. 'light' will receive discovery_info=None
def setup_platform(hass, config, add_devices, discovery_info=None):
    """Your switch/light specific code."""
    # You can now use hass.data[myflashyhub.DATA_MFH]

The load_platform method allows the platforms to be loaded without the need for any additional platform entries in your configuration.yaml file, which normally would have been:

#light:
#  platform: myflashyhub
#switch:
#  platform: myflashyhub