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    spi: gpio: No MISO does not imply no RX · 74e8d287
    Linus Walleij 提交于
    [ Upstream commit abf5feef3ff0cefade0c76be53b59e55fdd46093 ]
    
    There is a logical problem in spi-gpio with host just
    assigning a MOSI line and no MISO: this is interpreted
    as the host cannot do RX and the host is flagged with
    SPI_MASTER_NO_RX.
    
    This is wrong: since GPIO lines can switch direction,
    in 3WIRE operation the host will simply reverse the
    direction of the GPIO line and start reading from it,
    there is even code for doing this in the driver, but
    it went unnoticed because it was tested by using a
    master with 4 wires but a device using just 3 wires.
    
    Remove the offending flag.
    
    Cc: Andrzej Hajda <a.hajda@samsung.com>
    Cc: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
    Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>
    Signed-off-by: NMark Brown <broonie@kernel.org>
    Signed-off-by: NSasha Levin <sashal@kernel.org>
    Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    74e8d287
spi-gpio.c 13.8 KB