根据Device Tree生成Platform device

根据Device Tree生成Platformdevice

1.书写dts文件

要生成platformdevice，首先要定义一个dts文件，Device Tree机制根据这个dts文件生成platform device.

Documentation/devicetree/目录介绍了device tree的使用，dts的书写需要先阅读：

http://devicetree.org/Device_Tree_Usage

例如在arch/arm/boot/dts/目录下有exynos5420.dtsi文件

/ {

        compatible ="samsung,exynos5420", "samsung,exynos5";

}

其他dts文件可以像头文件一样包含dtsi文件

dtc可以将dts编译成二进制文件dtb，加载kernel时，dtb的物理地址作为参数传递给kernel，kernel解析dtb并生成device tree对应的platform device。

2.添加machine_desc结构体，例如arch/arm/mach-exynos/exynos.c

staticchar const *const exynos_dt_compat[] __initconst = {

        "samsung,exynos3",

        "samsung,exynos3250",

        "samsung,exynos4",

        "samsung,exynos4210",

        "samsung,exynos4212",

        "samsung,exynos4412",

        "samsung,exynos4415",

        "samsung,exynos5",

        "samsung,exynos5250",

        "samsung,exynos5260",

        "samsung,exynos5420",

        "samsung,exynos5440",

        NULL

};

….

DT_MACHINE_START(EXYNOS_DT,"SAMSUNG EXYNOS (Flattened Device Tree)")

        /* Maintainer: Thomas Abraham<thomas.abraham@linaro.org> */

        /* Maintainer: Kukjin Kim<kgene.kim@samsung.com> */

        .l2c_aux_val    = 0x3c400001,

        .l2c_aux_mask   = 0xc20fffff,

        .smp            = smp_ops(exynos_smp_ops),

        .map_io         = exynos_init_io,

        .init_early     = exynos_firmware_init,

        .init_irq       = exynos_init_irq,

        .init_machine   = exynos_dt_machine_init,

        .init_late      = exynos_init_late,

        .dt_compat      = exynos_dt_compat,

        .reserve        = exynos_reserve,

        .dt_fixup       = exynos_dt_fixup,

MACHINE_END

3. kernel解析dtb，生成platform device

init/main.c：：start_kernel

arch/arm/kernel/setup.c：：setup_arch