w1: add UART w1 bus driver

2024-02-15T14:02:33Z

Add a UART 1-Wire bus driver. The driver utilizes the UART interface via the Serial Device Bus to create the 1-Wire timing patterns. The driver was tested on a "Raspberry Pi 3B" with a DS18B20 and on a "Variscite DART-6UL" with a DS18S20 temperature sensor. The 1-Wire timing pattern and the corresponding UART baud-rate with the interpretation of the transferred bytes are described in the document: Link: https://www.analog.com/en/technical-articles/using-a-uart-to-implement-a-1wire-bus-master.html In short, the UART peripheral must support full-duplex and operate in open-drain mode. The timing patterns are generated by a specific combination of baud-rate and transmitted byte, which corresponds to a 1-Wire read bit, write bit or reset. Signed-off-by: Christoph Winklhofer Link: https://lore.kernel.org/r/20240214-w1-uart-v7-3-6e21fa24e066@gmail.com [krzysztof: w1_uart_serdev_receive_buf() return type fixup] Signed-off-by: Krzysztof Kozlowski

kernel/drivers/w1/masters/w1-uart.c, branch linux-6.9.y

w1: add UART w1 bus driver