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    SubjectRE: [PWM PATCH 2/5] Emulates PWM hardware using a high-resolution timer and a GPIO pin
    Date
    From
    Thursday, February 11, 2010 1:35 PM, Bill Gatliff wrote:
    > Pavel Machek wrote:
    >>> +static void
    >>> +gpio_pwm_work (struct work_struct *work)
    >>> +{
    >>> + struct gpio_pwm *gp = container_of(work, struct gpio_pwm, work);
    >>> +
    >>> + if (gp->active)
    >>> + gpio_direction_output(gp->gpio, gp->polarity ? 1 : 0);
    >>> + else
    >>> + gpio_direction_output(gp->gpio, gp->polarity ? 0 : 1);
    >>> +}
    >>>
    >>
    >> ...polarity ^ active ?
    >>
    >
    > ... except that if polarity and/or active are >1, I don't send the
    > values 1 or 0 to gpio_direction_output. I don't know if the API is
    > specifically intended to accept nonzero values that are greater than 1.

    FWIW, the gpiolib API will accept any non-zero value to "set" a gpio pin
    and a zero value to "clear" the pin.

    For that matter, some of the gpiolib drivers end up returning the bit
    position mask for a given gpio pin and not 1 or 0. For instance if the
    gpio pin in question is bit 6 in an 8-bit register and it is set, a
    __gpio_get_value will end up returning 0x40 and not '1'.

    Regards,
    Hartley


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