drivers/watchdog/riowd.c

File Facts

System

Linux kernel

Corpus path

drivers/watchdog/riowd.c

Extension

.c

Size

5723 bytes

Lines

245

Domain

Driver Families

Bucket

drivers/watchdog

Inferred role

Driver Families: operation-table or driver-model contract

Status

pattern implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

• Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.
• Defines an operation table; this is where Linux turns generic core objects into subsystem-specific behavior.
• Touches user memory; correctness depends on fault-safe copying and privilege boundary handling.
• Uses kernel synchronization; read lock ordering, sleepability, and interrupt context assumptions before translating.
• Allocates kernel memory; connect allocation flags and lifetime to context constraints.
• Defines or uses C structs; map object ownership, embedded links, reference counts, and lock ownership.

Dependency Surface

• linux/kernel.h
• linux/module.h
• linux/types.h
• linux/fs.h
• linux/errno.h
• linux/miscdevice.h
• linux/watchdog.h
• linux/of.h
• linux/platform_device.h
• linux/io.h
• linux/uaccess.h
• linux/slab.h

Detected Declarations

• struct riowd
• function riowd_writereg
• function riowd_open
• function riowd_release
• function riowd_ioctl
• function riowd_write
• function riowd_probe
• function riowd_remove

Annotated Snippet

static const struct file_operations riowd_fops = {
	.owner =		THIS_MODULE,
	.unlocked_ioctl =	riowd_ioctl,
	.compat_ioctl	=	compat_ptr_ioctl,
	.open =			riowd_open,
	.write =		riowd_write,
	.release =		riowd_release,
};

static struct miscdevice riowd_miscdev = {
	.minor	= WATCHDOG_MINOR,
	.name	= "watchdog",
	.fops	= &riowd_fops
};

static int riowd_probe(struct platform_device *op)
{
	struct riowd *p;
	int err = -EINVAL;

	if (riowd_device)
		goto out;

	err = -ENOMEM;
	p = devm_kzalloc(&op->dev, sizeof(*p), GFP_KERNEL);
	if (!p)
		goto out;

	spin_lock_init(&p->lock);

	p->regs = of_ioremap(&op->resource[0], 0, 2, DRIVER_NAME);
	if (!p->regs) {
		pr_err("Cannot map registers\n");
		goto out;
	}
	/* Make miscdev useable right away */
	riowd_device = p;

	err = misc_register(&riowd_miscdev);
	if (err) {
		pr_err("Cannot register watchdog misc device\n");
		goto out_iounmap;
	}

	pr_info("Hardware watchdog [%i minutes], regs at %p\n",
		riowd_timeout, p->regs);

	platform_set_drvdata(op, p);
	return 0;

out_iounmap:
	riowd_device = NULL;
	of_iounmap(&op->resource[0], p->regs, 2);

out:
	return err;
}

static void riowd_remove(struct platform_device *op)
{
	struct riowd *p = platform_get_drvdata(op);

	misc_deregister(&riowd_miscdev);
	of_iounmap(&op->resource[0], p->regs, 2);
}

static const struct of_device_id riowd_match[] = {
	{
		.name = "pmc",
	},
	{},
};
MODULE_DEVICE_TABLE(of, riowd_match);

static struct platform_driver riowd_driver = {
	.driver = {
		.name = DRIVER_NAME,
		.of_match_table = riowd_match,
	},
	.probe		= riowd_probe,
	.remove		= riowd_remove,
};

module_platform_driver(riowd_driver);

Annotation

• Immediate include surface: `linux/kernel.h`, `linux/module.h`, `linux/types.h`, `linux/fs.h`, `linux/errno.h`, `linux/miscdevice.h`, `linux/watchdog.h`, `linux/of.h`.
• Detected declarations: `struct riowd`, `function riowd_writereg`, `function riowd_open`, `function riowd_release`, `function riowd_ioctl`, `function riowd_write`, `function riowd_probe`, `function riowd_remove`.
• Atlas domain: Driver Families / drivers/watchdog.
• Implementation status: pattern implementation candidate.
• This snippet crosses the user/kernel memory boundary; validate fault handling and access checks before translating the pattern.
• Synchronization appears in or near this file; preserve lock ordering, sleepability, and interrupt-context constraints.

Implementation Notes

• This generated page is the file-by-file coverage layer; curated subsystem chapters should link here when they synthesize a multi-file control flow.
• Core OS pages should be promoted from atlas-only to deep-reviewed when they explain data structures, invariants, locking, lifecycle, and C implementation snippets.
• Driver-family pages are intentionally pattern-oriented unless they are part of the selected PCIe/NVMe representative device path.