add new system file

hc

2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/drivers/spi/spi-gpio.c
..
..
@@ -244,9 +244,19 @@
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 	if (output)
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 		return gpiod_direction_output(spi_gpio->mosi, 1);
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-	ret = gpiod_direction_input(spi_gpio->mosi);
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-	if (ret)
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-		return ret;
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+	/*
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+	 * Only change MOSI to an input if using 3WIRE mode.
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+	 * Otherwise, MOSI could be left floating if there is
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+	 * no pull resistor connected to the I/O pin, or could
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+	 * be left logic high if there is a pull-up. Transmitting
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+	 * logic high when only clocking MISO data in can put some
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+	 * SPI devices in to a bad state.
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+	 */
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+	if (spi->mode & SPI_3WIRE) {
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+		ret = gpiod_direction_input(spi_gpio->mosi);
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+		if (ret)
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+			return ret;
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+	}
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 	/*
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 	 * Send a turnaround high impedance cycle when switching
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 	 * from output to input. Theoretically there should be