platform-device-model

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🇺🇸

Original

English

🇨🇳

Translation

Chinese

Platform Device Model

平台设备模型

Purpose

用途

Explain the Linux driver model for platform (and similar) buses:

struct device

device_driver

probe

remove

, resource acquisition, sysfs, and deferred probe — the glue between device tree and driver code.

讲解适用于平台（及类似）总线的Linux驱动模型：

struct device

、

device_driver

、

probe

remove

、资源获取、sysfs以及延迟探测——这是设备树与驱动代码之间的衔接机制。

When to Use

适用场景

Implementing or debugging
```
platform_driver
```
lifecycle
Exposing driver state via sysfs
Understanding uevent /
```
udev
```
device node creation
Before
```
skills/kernel-dev/writing-char-drivers
```

实现或调试
```
platform_driver
```
生命周期
通过sysfs暴露驱动状态
理解uevent /
```
udev
```
设备节点创建逻辑
在学习
```
skills/kernel-dev/writing-char-drivers
```
之前

Workflow

工作流程

1. Object hierarchy

1. 对象层级

bus_type (platform, amba, pci, i2c, spi)
├── struct device        — hardware instance
└── struct device_driver — driver logic
        └── probe(dev) / remove(dev)

Platform devices often come from DT (

of_platform

) or legacy board files.

bus_type (platform, amba, pci, i2c, spi)
├── struct device        — 硬件实例
└── struct device_driver — 驱动逻辑
        └── probe(dev) / remove(dev)

平台设备通常来自设备树（

of_platform

）或传统板级文件。

2. Platform driver skeleton

2. 平台驱动框架

static int my_probe(struct platform_device *pdev)
{
    struct resource *res;
    void __iomem *base;

    res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    base = devm_ioremap_resource(&pdev->dev, res);
    if (IS_ERR(base))
        return PTR_ERR(base);

    platform_set_drvdata(pdev, priv);
    return 0;
}

static void my_remove(struct platform_device *pdev)
{
    /* devm_* auto-cleanup on remove */
}

static struct platform_driver my_pdrv = {
    .probe  = my_probe,
    .remove = my_remove,
    .driver = {
        .name = "my-dev",
        .of_match_table = my_of_match,
    },
};
module_platform_driver(my_pdrv);

Prefer

devm_*

helpers for automatic unwind.

static int my_probe(struct platform_device *pdev)
{
    struct resource *res;
    void __iomem *base;

    res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    base = devm_ioremap_resource(&pdev->dev, res);
    if (IS_ERR(base))
        return PTR_ERR(base);

    platform_set_drvdata(pdev, priv);
    return 0;
}

static void my_remove(struct platform_device *pdev)
{
    /* devm_* 会在移除时自动清理 */
}

static struct platform_driver my_pdrv = {
    .probe  = my_probe,
    .remove = my_remove,
    .driver = {
        .name = "my-dev",
        .of_match_table = my_of_match,
    },
};
module_platform_driver(my_pdrv);

优先使用

devm_*

辅助函数实现自动资源释放。

3. Device properties (DT / ACPI)

3. 设备属性（DT / ACPI）

u32 speed;
device_property_read_u32(&pdev->dev, "clock-speed", &speed);
bool flag = device_property_present(&pdev->dev, "feature-x");

u32 speed;
device_property_read_u32(&pdev->dev, "clock-speed", &speed);
bool flag = device_property_present(&pdev->dev, "feature-x");

4. Sysfs (driver visibility)

4. Sysfs（驱动可见性）

static ssize_t status_show(struct device *dev,
                           struct device_attribute *attr, char *buf)
{
    return sysfs_emit(buf, "ok\n");
}
static DEVICE_ATTR_RO(status);

/* in probe */
device_create_file(&pdev->dev, &dev_attr_status);

static ssize_t status_show(struct device *dev,
                           struct device_attribute *attr, char *buf)
{
    return sysfs_emit(buf, "ok\n");
}
static DEVICE_ATTR_RO(status);

/* 在probe中调用 */
device_create_file(&pdev->dev, &dev_attr_status);

5. Deferred probe

5. 延迟探测

Return

-EPROBE_DEFER

when a clock, regulator, or bus is not ready — core retries later.

当时钟、调节器或总线未就绪时返回

-EPROBE_DEFER

——内核核心层会稍后重试。

6. Debug

6. 调试

bash

ls /sys/bus/platform/devices/
ls /sys/bus/platform/drivers/
cat /sys/kernel/debug/devices_deferred  # if debugfs enabled
udevadm monitor