drivers/s390/char/monwriter.c

File Facts

System

Linux kernel

Corpus path

drivers/s390/char/monwriter.c

Extension

.c

Size

7953 bytes

Lines

321

Domain

Driver Families

Bucket

drivers/s390

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/module.h
• linux/moduleparam.h
• linux/init.h
• linux/errno.h
• linux/types.h
• linux/kernel.h
• linux/miscdevice.h
• linux/ctype.h
• linux/poll.h
• linux/mutex.h
• linux/slab.h
• linux/uaccess.h
• linux/io.h
• asm/machine.h
• asm/ebcdic.h
• asm/appldata.h
• asm/monwriter.h

Detected Declarations

• struct mon_buf
• struct mon_private
• function monwrite_diag
• function monwrite_new_hdr
• function monwrite_new_data
• function monwrite_open
• function monwrite_close
• function list_for_each_entry_safe
• function monwrite_write
• function mon_init
• function mon_exit
• module init mon_init

Annotated Snippet

static const struct file_operations monwrite_fops = {
	.owner	 = THIS_MODULE,
	.open	 = &monwrite_open,
	.release = &monwrite_close,
	.write	 = &monwrite_write,
	.llseek  = noop_llseek,
};

static struct miscdevice mon_dev = {
	.name	= "monwriter",
	.fops	= &monwrite_fops,
	.minor	= MISC_DYNAMIC_MINOR,
};

/*
 * module init/exit
 */

static int __init mon_init(void)
{
	if (!machine_is_vm())
		return -ENODEV;
	/*
	 * misc_register() has to be the last action in module_init(), because
	 * file operations will be available right after this.
	 */
	return misc_register(&mon_dev);
}

static void __exit mon_exit(void)
{
	misc_deregister(&mon_dev);
}

module_init(mon_init);
module_exit(mon_exit);

module_param_named(max_bufs, mon_max_bufs, int, 0644);
MODULE_PARM_DESC(max_bufs, "Maximum number of sample monitor data buffers "
		 "that can be active at one time");

MODULE_AUTHOR("Melissa Howland <Melissa.Howland@us.ibm.com>");
MODULE_DESCRIPTION("Character device driver for writing z/VM "
		   "APPLDATA monitor records.");
MODULE_LICENSE("GPL");

Annotation

• Immediate include surface: `linux/module.h`, `linux/moduleparam.h`, `linux/init.h`, `linux/errno.h`, `linux/types.h`, `linux/kernel.h`, `linux/miscdevice.h`, `linux/ctype.h`.
• Detected declarations: `struct mon_buf`, `struct mon_private`, `function monwrite_diag`, `function monwrite_new_hdr`, `function monwrite_new_data`, `function monwrite_open`, `function monwrite_close`, `function list_for_each_entry_safe`, `function monwrite_write`, `function mon_init`.
• Atlas domain: Driver Families / drivers/s390.
• 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.