s5pv210 设备树分析——keypad

移植网卡失败，所以先来学习一下dts的使用方法。
keypad是最简单的设备之一，所以先拿这个开刀。
在s5pv210.dtsi里列举了s5pv210的soc上面的所有设备资源，注意这里是soc上的，没有描述实际连接的外设，实际的外设需要在主dts也就是s5pv210-smdkv210.dts中描述。

/ {
.....................

        pinctrl0: pinctrl@e0200000 {
            compatible = "samsung,s5pv210-pinctrl";
            reg = <0xe0200000 0x1000>;
            interrupt-parent = <&vic0>;
            interrupts = <30>;

            wakeup-interrupt-controller {
                compatible = "samsung,exynos4210-wakeup-eint";
                interrupts = <16>;
                interrupt-parent = <&vic0>;
            };
        };

        keypad: keypad@e1600000 {
            compatible = "samsung,s5pv210-keypad";
            reg = <0xe1600000 0x1000>;
            interrupt-parent = <&vic2>;
            interrupts = <25>;
            clocks = <&clocks CLK_KEYIF>;
            clock-names = "keypad";
            status = "disabled";
        };

pinctrl是GPIO设备为什么长度只有0x1000，我猜测这个pinctrl的作用只是给驱动源码提供一个GPIO的base address。
这里定义了一个标签keypad，方便其他地方引用。
keypad的寄存器地址是e1600000，这和手册是一致的。属性指定了中断，时钟。
但是具体用到那些gpio呢，这就要看s5pv210-smdkv210.dts了。

&keypad {
    linux,input-no-autorepeat;
    linux,input-wakeup;
    samsung,keypad-num-rows = <8>;
    samsung,keypad-num-columns = <8>;
    pinctrl-names = "default";
    pinctrl-0 = <&keypad_row0>, <&keypad_row1>, <&keypad_row2>,
            <&keypad_row3>, <&keypad_row4>, <&keypad_row5>,
            <&keypad_row6>, <&keypad_row7>,
            <&keypad_col0>, <&keypad_col1>, <&keypad_col2>,
            <&keypad_col3>, <&keypad_col4>, <&keypad_col5>,
            <&keypad_col6>, <&keypad_col7>;
    status = "okay";

    key_1 {
        keypad,row = <0>;
        keypad,column = <3>;
        linux,code = <KEY_1>;
    };

    key_2 {
        keypad,row = <0>;
        keypad,column = <4>;
        linux,code = <KEY_2>;
    };

    key_3 {
        keypad,row = <0>;
        keypad,column = <5>;
        linux,code = <KEY_3>;
    };

    key_4 {
        keypad,row = <0>;
        keypad,column = <6>;
        linux,code = <KEY_4>;
    };

    key_5 {
        keypad,row = <0
        >;
        keypad,column = <7>;
        linux,code = <KEY_5>;
    };

    key_6 {
        keypad,row = <1>;
        keypad,column = <3>;
        linux,code = <KEY_A>;
    };
    key_7 {
        keypad,row = <1>;
        keypad,column = <4>;
        linux,code = <KEY_B>;
    };

    key_8 {
        keypad,row = <1>;
        keypad,column = <5>;
        linux,code = <KEY_C>;
    };

    key_9 {
        keypad,row = <1>;
        keypad,column = <6>;
        linux,code = <KEY_D>;
    };

    key_10 {
        keypad,row = <1>;
        keypad,column = <7>;
        linux,code = <KEY_E>;
    };
};

通过&keypad引用s5pv210.dtsi中的keypad结点。我的理解就是对s5pv210.dtsi中的keypad结点添加更多属性。
这个keypad的设置为：
禁止重复按键输入，输入唤醒，8行8列。注意pinctrl-0=<&keypad_row0>    ~    <&keypad_col7>，这是重头戏，通过标签引用了16根引脚结点，这些引脚在s5pv210-pinctrl.dts中定义。
这是一个典型的client device结点（pinctrl子系统中的概念），state只有一个"default"，相关知识参考 style="white-space:normal;" /> default的状态对应了pinctrl-0的配置，也就是当keypad这个设备被激活的时候，将这16根引脚设置成pinctrl-0的配置。pinctrl-0是一个句柄（phandle）列表，指向<&keypad_row0>   ~    <&keypad_col7>。

s5pv210-pinctrl.dts列出了pinctrl0的全部结点，这里只给出keypad相关的结点：

&pinctrl0 {

........

       keypad_row0: keypad-row-0 {
        samsung,pins = "gph3-0";
        samsung,pin-function = <3>;
        samsung,pin-pud = <0>;
        samsung,pin-drv = <0>;
    };

    keypad_row1: keypad-row-1 {
        samsung,pins = "gph3-1";
        samsung,pin-function = <3>;
        samsung,pin-pud = <0>;
        samsung,pin-drv = <0>;
    };

    keypad_row2: keypad-row-2 {
        samsung,pins = "gph3-2";
        samsung,pin-function = <3>;
        samsung,pin-pud = <0>;
        samsung,pin-drv = <0>;
    };

    keypad_row3: keypad-row-3 {
        samsung,pins = "gph3-3";
        samsung,pin-function = <3>;
        samsung,pin-pud = <0>;
        samsung,pin-drv = <0>;
    };

    keypad_row4: keypad-row-4 {
        samsung,pins = "gph3-4";
        samsung,pin-function = <3>;
        samsung,pin-pud = <0>;
        samsung,pin-drv = <0>;
    };

    keypad_row5: keypad-row-5 {
        samsung,pins = "gph3-5";
        samsung,pin-function = <3>;
        samsung,pin-pud = <0>;
        samsung,pin-drv = <0>;
    };

    keypad_row6: keypad-row-6 {
        samsung,pins = "gph3-6";
        samsung,pin-function = <3>;
        samsung,pin-pud = <0>;
        samsung,pin-drv = <0>;
    };

    keypad_row7: keypad-row-7 {
        samsung,pins = "gph3-7";
        samsung,pin-function = <3>;
        samsung,pin-pud = <0>;
        samsung,pin-drv = <0>;
    };

    keypad_col0: keypad-col-0 {
        samsung,pins = "gph2-0";
        samsung,pin-function = <3>;
        samsung,pin-pud = <0>;
        samsung,pin-drv = <0>;
    };

    keypad_col1: keypad-col-1 {
        samsung,pins = "gph2-1";
        samsung,pin-function = <3>;
        samsung,pin-pud = <0>;
        samsung,pin-drv = <0>;
    };

    keypad_col2: keypad-col-2 {
        samsung,pins = "gph2-2";
        samsung,pin-function = <3>;
        samsung,pin-pud = <0>;
        samsung,pin-drv = <0>;
    };

    keypad_col3: keypad-col-3 {
        samsung,pins = "gph2-3";
        samsung,pin-function = <3>;
        samsung,pin-pud = <0>;
        samsung,pin-drv = <0>;
    };

    keypad_col4: keypad-col-4 {
        samsung,pins = "gph2-4";
        samsung,pin-function = <3>;
        samsung,pin-pud = <0>;
        samsung,pin-drv = <0>;
    };

    keypad_col5: keypad-col-5 {
        samsung,pins = "gph2-5";
        samsung,pin-function = <3>;
        samsung,pin-pud = <0>;
        samsung,pin-drv = <0>;
    };

    keypad_col6: keypad-col-6 {
        samsung,pins = "gph2-6";
        samsung,pin-function = <3>;
        samsung,pin-pud = <0>;
        samsung,pin-drv = <0>;
    };

    keypad_col7: keypad-col-7 {
        samsung,pins = "gph2-7";
        samsung,pin-function = <3>;
        samsung,pin-pud = <0>;
        samsung,pin-drv = <0>;
    };

这里定义了keypad_row0   ~    keypad_col7 共16个标签，就是刚才的&keypad中的pinctrl-0引用了，这里详细列出了当使用keypad时，16个io的配置。
到这里就分析完成了。
补充说明一下s5pv210.dts中的aliaes（别名）。

/ {
    aliases {
        csis0 = &csis0;
        fimc0 = &fimc0;
        fimc1 = &fimc1;
        fimc2 = &fimc2;
        i2c0 = &i2c0;
        i2c1 = &i2c1;
        i2c2 = &i2c2;
        i2s0 = &i2s0;
        i2s1 = &i2s1;
        i2s2 = &i2s2;
        pinctrl0 = &pinctrl0;
        spi0 = &spi0;
        spi1 = &spi1;
    };

注意这里pinctrl0 = &pinctrl0;    这行代码相当于C语言中的宏定义。可以理解为#define  pinctrl0 &pinctrl0;

这样当我们在属性中写pinctrl0时，就是用&符号引用标签pinctrl0，乍一看可能感觉没什么卵用，直接写&pinctrl0不就完了，事实并非如此，对于dts文件可以用&pinctrl0的方式引用结点，但是在内核驱动源码中，就必须指定全路径了，所以这里用别名来替代全路径，方便驱动源码的识别。在根据device tree usage，别名应当是用来替代全路径的。