I,m tryingin use w1-gpio and w1-gpio-pullup on parasitic mode, but it seems that current kernel do not support pullup=1 option. Both drivers gives on dmessage same info:
w1_add_master_device: set_pullup requires write_byte or touch_bit, disabling
When checking io-pin with scope, there is no sharp up edeges on DQ so dmesg gives right status, active pull up is disable. Also with w1-gpio-pullup there is no any activity on second gpio. Second gpio should drive external mosfet for pulling up DQ during data idle time for chargin parasitic capacitor on 1-wire sensor.
Proper functionality for w1-gpio-pullup second io-pin is explained on ds18b20 datasheet or any other 1-wire documents. With settings:
gpio4 is for DQ data only and gpio5 is high during data trasmissin (mosfet not pulling DQ high) and low during DQ idle time(mosfet pulling DQ high).
Is there any plans to add support pullup=1 option for w1-gpio and w1-gpio-pullup driver?