home-assistant.io/source/developers/component_generic_discovery.markdown

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layout	title	description	date	sidebar	comments	sharing	footer
page	Generic Platform Discovery	Using generic platform discovery.	2016-05-12 22:00 -02:00	true	false	true	true

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 homeassistant.components.discovery.load_platform method:

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

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

{% linkable_title 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.components.discovery import load_platform
DOMAIN = 'myflashyhub'

MFH_GLOBAL = None

def setup(hass, config):
    """Your controller/hub specific code."""
    
    global MFH_GLOBAL
    if MFH_GLOBAL is None:
        MFH_GLOBAL = 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 homeassistant.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 myflashyhub.MFH_GLOBAL

The load_platform method allows the platforms to be loaded with the need for any additional platform entries in your configuration.yaml file, which normally would have been:

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

In the past, this was achieved by adding your component to the `DISCOVERY_PLATFORMS` in the target sub-component. Generic discovery through `load_platform()` allows you to load any sub-component, including custom components, without changing the sub-component.