------------------------------------
dtc -I dts -O dtb -S 0x3000 -o obj_name.dtb source_name.dts
-S 指定的是生成的dtb文件的大小，需要适当地扩大，以供u-boot创建/choose节点时使用
查看dts设备节点
------------------------------------
# ls -al /proc/device-tree
内核如何解析设备树
------------------------------------
1) 首先将从u-boot 传递过来的映像基地址和dtb 文件映像基地址保存通用寄存器r30,r31；
2) 通过调用machine_init() --> early_init_devtree()函数来获
取内核前期初始化所需的bootargs,cmd_line等系统引导参数；
3) 调用start_kernel() --> setup_arch() -->
unflatten_device_tree()函数来解析dtb文件，构建一个由device_node结构连接而成的单项链表，并使用全局变量allnodes指针来保存这个链表的头指针；
4) 内核调用OF提供的API函数获取allnodes链表信息来初始化内核其他子系统、设备等。
dispAllnodes() -- 显示DTS设备节点
--------------------------------------
./arch/powerpc/kernel/prom.c
void dispAllnodes()
{
struct device_node *dn;
dn = allnodes;
while (dn)
{
printk("dn->name = %s\n", dn->name);
printk("dn->type = %s\n", dn->type);
printk("dn->full_name = %s\n", dn->full_name);
printk("\n");
dn = dn->next;
}
}
EXPORT_SYMBOL(dispAllnodes);
根据DTS文件的设备节点，添加设备
linux-2.6.28\arch\powerpc\boot\dts\mpc8548cds.dts
-------------------------------------------------------
soc8548@e0000000 {
#address-cells = <1>;
#size-cells = <1>;
device_type = "soc";
ranges = <0 e0000000 00100000>;
reg =
bus-frequency = <0>;
mdio@24520 {
#address-cells = <1>;
#size-cells = <0>;
device_type = "mdio";
compatible = "gianfar";
reg = <24520 20>;
phy0: ethernet-phy@0 {
interrupt-parent = <&mpic>;
interrupts = <35 0>;
reg = <0>;
device_type = "ethernet-phy";
};
};
linux-2.6.21.7
gfar_mdio_of_init() -->
platform_device_register_simple() -->
platform_device_add() -->
device_add()
将mdio设备节点添加到platform总线上，这样添加方式(单独添加某个节点)
比较麻烦，抽象度不够，每个节点都需要自己的添加代码，不科学
还是of_platform_bus_probe()比较好，统一添加allnodes下的所有节点
-------------------------------------------------------
{
...
// 获取device_type = "mdio" && compatible = "gianfar"的设备节点
np = of_find_compatible_node(np, "mdio", "gianfar"));
of_address_to_resource(np, 0, &res);
// 添加平台设备res.start = e0024520
platform_device_register_simple("fsl-gianfar_mdio", res.start, &res, 1);
...
}
arch_initcall(gfar_mdio_of_init);
struct platform_device *platform_device_register_simple(char *name,
unsigned int id,
struct resource *res, unsigned int num)
{
...
// 生成platform_device
// platform_device->name = name; "fsl-gianfar_mdio"
// platform_device->id = id; e0024520
pdev = platform_device_alloc(name, id);
...
platform_device_add(pdev);
...
}
int platform_device_add(struct platform_device *pdev)
{
...
// 设置pdev->dev.bus_id = fsl-gianfar_mdio.e0024520
// bus_id长度限制为BUS_ID_SIZE
// #define BUS_ID_SIZE KOBJ_NAME_LEN
// 如果"%s.%x"字符串的长度超过KOBJ_NAME_LEN，将会造成设备节点名信息丢失
// 信息的丢失有可能导致设备添加失败，所以需要将KOBJ_NAME_LEN改大(20 --> 64)
snprintf(pdev->dev.bus_id, BUS_ID_SIZE, "%s.%x", pdev->name, pdev->id);
...
device_add(&pdev->dev);
...
}
int device_add(struct device *dev)
{
...
// 设置kobject->name = fsl-gianfar_mdio.e0024520
// #define KOBJ_NAME_LEN 20
kobject_set_name(&dev->kobj, "%s", dev->bus_id);
...
// 在/sys/devices/platform/目录下生成设备节点
// 设备节点名称为fsl-gianfar_mdio.e0024520
device_create_file(dev, &dev->uevent_attr);
...
}
设备与驱动的对应关系
-----------------------------------------------------
static struct device_driver gianfar_mdio_driver = {
.name = "fsl-gianfar_mdio",
.bus = &platform_bus_type, //该驱动所归属的总线
.probe = gfar_mdio_probe,
.remove = gfar_mdio_remove,
};
cat /sys/devices/platform/fsl-gianfar_mdio.e0024520/modalias
fsl-gianfar_mdio
static struct platform_driver gfar_driver = {
.probe = gfar_probe,
.remove = gfar_remove,
.driver = {
.name = "fsl-gianfar",
},
};
cat /sys/devices/platform/fsl-gianfar.0/modalias
fsl-gianfar