platform-device-model

Original：🇺🇸 English

Translated

Platform device model skill for Linux driver binding. Use when implementing platform_driver probe/remove, sysfs attributes, device properties, or deferred probe. Activates on queries about platform_device, platform_driver, driver model, sysfs, probe remove, or Linux device bus.

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Sourcemohitmishra786/low-level-dev-skills

Added on2026-08-20

NPX Install

npx skill4agent add mohitmishra786/low-level-dev-skills platform-device-model

SKILL.md Content

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Platform Device Model

Purpose

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.

When to Use

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

Workflow

1. Object hierarchy

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.

2. Platform driver skeleton

c

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.

3. Device properties (DT / ACPI)

c

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

4. Sysfs (driver visibility)

c

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);

5. Deferred probe

Return

-EPROBE_DEFER

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

6. Debug

bash

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

7. Agent usage

/platform-device-model Convert legacy board file driver to DT platform_driver with devm_ioremap

Common Problems

Symptom	Cause	Fix
`-EBUSY` on probe	Resource claimed twice	Check `status` / duplicate nodes
No `/dev` node	Char device not registered	See `writing-char-drivers`
Deferred forever	Supplier driver missing	Fix DT dependency chain
Remove crash	Manual free vs devm mismatch	Use devm consistently
Name mismatch	`.name` vs `compatible`	OF uses `of_match_table`

Related Skills

```
skills/kernel-dev/device-tree
```
— hardware description
```
skills/kernel/device-drivers
```
— IRQ, DMA, regmap depth
```
skills/kernel-dev/writing-char-drivers
```
— userspace interface
```
skills/kernel-dev/bus-drivers-i2c-spi
```
— other bus types

skills/low-level-programming/linux-kernel-modules

— module loading