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    SubjectRe: [PATCH 1/2] gpio: add a custom configuration mechanism to gpiolib
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    On Wed, Apr 20, 2011 at 6:00 PM, Linus Walleij
    <linus.walleij@stericsson.com> wrote:
    > diff --git a/include/linux/gpio.h b/include/linux/gpio.h
    > index 32720ba..fa92e50 100644
    > --- a/include/linux/gpio.h
    > +++ b/include/linux/gpio.h
    > @@ -3,6 +3,60 @@
    >
    >  /* see Documentation/gpio.txt */
    >
    > +/*
    > + * Bias modes for GPIOs - if you have more biases, add them here or provide
    > + * custom enumerators for your driver if you find they are not generally
    > + * useful.
    > + *
    > + * GPIO_CONFIG_BIAS_UNKNOWN: this bias mode is not known to us
    > + * GPIO_CONFIG_BIAS_FLOAT: no specific bias, the GPIO will float or state
    > + *     is not controlled by software
    > + * GPIO_CONFIG_BIAS_PULL_UP: the GPIO will be pulled up (usually with high
    > + *     impedance to VDD)
    > + * GPIO_CONFIG_BIAS_PULL_DOWN: the GPIO will be pulled down (usually with high
    > + *     impedance to GROUND)
    > + * GPIO_BIAS_HIGH: the GPIO will be wired high, connected to VDD
    > + * GPIO_BIAS_GROUND: the GPIO will be grounded, connected to GROUND
    > + */
    > +#define GPIO_CONFIG_BIAS_UNKNOWN       0x1000
    > +#define GPIO_CONFIG_BIAS_FLOAT         0x1001
    > +#define GPIO_CONFIG_BIAS_PULL_UP       0x1002
    > +#define GPIO_CONFIG_BIAS_PULL_DOWN     0x1003
    > +#define GPIO_CONFIG_BIAS_HIGH          0x1004
    > +#define GPIO_CONFIG_BIAS_GROUND                0x1005
    > +
    Why contain all values in the config rather than
    // Actual config
    #define GPIO_CONFIG_BIAS 0x1

    #define GPIO_BIAS_UNKNOWN 0x0
    #define GPIO_BIAS_FLOAT 0x1
    #define GPIO_BIAS_PULL_UP 0x2
    #define GPIO_BIAS_PULL_DOWN 0x3
    #define GPIO_BIAS_HIGH 0x4
    #define GPIO_BIAS_GROUND 0x5
    #define GPIO_BIAS_ARCH_SPECIFIC 0x100

    #define GPIO_CONFIG_DRIVE 0x2
    /// omitted rest

    #define GPIO_CONFIG_COMPLEX_SAMPLE 0x3
    struct gpio_complex_sample_config
    {
    // whatever here
    };

    // code:
    gpio_config(10, GPIO_CONFIG_BIAS, GPIO_BIAS_FLOAT);
    struct gpio_complex_sample_config config = { ... };
    gpio_config(10, GPIO_CONFIG_COMPLEX_SAMPLE, &config);

    Other than that I definitely like the heading of this.

    I think a nice end-goal would be to allow a driver/board code to do
    something like
    pin = of_gpio_request_setup(device_node, index);
    pin = gpio_request(gpio_platform_data);
    gpio_request(10, list_of_config_options);
    to obtain a fully setup gpio pin where configuration is passed
    transparently through platform-data, device-tree or built up by
    the driver/board-code.

    Device-tree support can be added on top by having (reusable) generic
    and custom xlate functions (perhaps referring to the generic ones).
    Something similar could probably also be implemented for platform-data.

    Regards,
    Stijn
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