const registers = packed struct {
    moder: u32,
    otyper: u32,
    ospeedr: u32,
    pupdr: u32,
    idr: u32,
    odr: u32,
    bsrr: u32,
    lckr: u32,
    afrl: u32,
    afrh: u32,
    brr: u32,
    ascr: u32,
};

const driver = struct {
    port: *registers,

    const mode = enum {
        input,
        output,
        alternate,
        analog,
    };

    pub fn set_mode(self: driver, pin: u4, m: mode) void {
        self.port.moder &= ~(@as(u32, 0x3) << (2 * pin));

        const mask: u32 = switch (m) {
            .input => 0,
            .output => 1,
            .alternate => 2,
            .analog => 3
        };

        self.port.moder |= mask << (2 * pin);
    }

    pub fn toggle(self: driver, pin: u4) void {
        self.port.odr ^= @as(u32, 1) << pin;
    }
};

pub const gpioa = driver { .port = @ptrFromInt(0x48000000) };