• Linus Walleij's avatar
    w1: w1-gpio: Convert to use GPIO descriptors · e0fc62a6
    Linus Walleij authored
    The w1 master driver includes a complete open drain emulation
    reimplementation among other things.
    
    This converts the driver and all board files using it to use
    GPIO descriptors associated with the device to look up the
    GPIO wire, as well ass the optional pull-up GPIO line.
    
    When probed from the device tree, the driver will just pick
    descriptors and use them right off. For the two board files
    in the kernel, we add descriptor lookups so we do not need
    to keep any old platform data handling around for the GPIO
    lines.
    
    As the platform data is also a state container for this driver,
    we augment it to contain the GPIO descriptors.
    
    w1_gpio_write_bit_dir() and w1_gpio_write_bit_val() are gone
    since this pair was a reimplementation of open drain emulation
    which is now handled by gpiolib.
    
    The special "linux,open-drain" flag is a bit of mishap here:
    it has the same semantic as the same flags in I2C: it means
    that something in the platform is setting up the line as
    open drain behind our back. We handle this the same way as
    in I2C.
    
    To drive the pull-up, we need to bypass open drain emulation
    in gpiolib for the line, and this is done by driving it high
    using gpiod_set_raw_value() which has been augmented to have
    the semantic of overriding the open drain emulation.
    
    We also augment the documentation to reflect the way to pass
    GPIO descriptors from the machine.
    Acked-by: default avatarEvgeniy Polyakov <zbr@ioremap.net>
    Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
    e0fc62a6
raumfeld.c 26.4 KB