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    SubjectRe: [PATCH 1/2] gpio: add pin biasing and drive mode to gpiolib
    2011/4/19 Ben Nizette <>:

    > It just doesn't make sense to me to bounce from the board code in to
    > 'generic' gpio code then back to platform-specific implementations when
    > you could cut out the middle man.

    In the demonstrated case the U300 GPIO controller has a number
    of registers banks per 8-bit port, the U300 GPIO driver in
    drivers/gpio/u300-cgpio.c knows the physical whereabouts of
    these registers. So it maps them into virtual memory and
    manipulate them.

    Now to configure a pin from the board code without calling out
    to the GPIO subsystem you need to map the same registers
    into virtual memory a second time from board-u300-gpio.c,
    provide custom set-up functions there and manipulate the
    same register range from another place.

    This is intuitively bad design to me, it's better to compartmentalize
    the GPIO pin handling and whatever it takes into *one*
    driver file, not two drivers writing into the same register
    range, thanks.

    Linus Walleij

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