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This function grabs the i2c character device path from the OF_NAME property. That property must be unique in the device tree!
36 lines
1.2 KiB
Python
36 lines
1.2 KiB
Python
#
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# Copyright 2018 Ettus Research, a National Instruments Company
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#
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# SPDX-License-Identifier: GPL-3.0-or-later
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#
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"""
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Utilities for i2c lookups
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"""
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import pyudev
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def of_get_i2c_adapter(of_name):
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"""
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Return bus adapter device for given device tree name. To use the OF_NAME
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for matching (as this function does), it must be a unique property in the
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device tree (and this must be a device-tree platform).
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The return value is a string, e.g. '/dev/i2c-0'. If nothing is found, it'll
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return None.
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"""
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# If has i2c-dev, follow to grab i2c-%d node
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context = pyudev.Context()
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parents = list(context.list_devices(subsystem="i2c-adapter", OF_NAME=of_name))
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if len(parents) > 1:
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raise RuntimeError("Non-unique OF_NAME when getting i2c bus id")
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if len(parents) == 0:
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return None
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parent = parents[0]
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if not parent:
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return None
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devices = list(context.list_devices(parent=parent, subsystem="i2c-dev"))
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properties = [dict(d.properties) for d in devices]
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# The i2c-adapter will have the lowest minor number
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# FIXME: This likely isn't API--It just happens to work as of this writing
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chosen = min([(int(p['MINOR']), p['DEVNAME']) for p in properties])
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return chosen[1]
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