arch/um/drivers/hostaudio_kern.c

File Facts

System

Linux kernel

Corpus path

arch/um/drivers/hostaudio_kern.c

Extension

.c

Size

7711 bytes

Lines

354

Domain

Architecture Layer

Bucket

arch/um

Inferred role

Architecture Layer: operation-table or driver-model contract

Status

pattern implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

• CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.
• 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/fs.h
• linux/module.h
• linux/slab.h
• linux/sound.h
• linux/soundcard.h
• linux/mutex.h
• linux/uaccess.h
• init.h
• os.h

Detected Declarations

• struct hostaudio_state
• struct hostmixer_state
• function set_dsp
• function set_mixer
• function hostaudio_read
• function hostaudio_write
• function hostaudio_poll
• function hostaudio_ioctl
• function hostaudio_open
• function hostaudio_release
• function hostmixer_ioctl_mixdev
• function hostmixer_open_mixdev
• function hostmixer_release
• function hostaudio_init_module
• function hostaudio_cleanup_module
• module init hostaudio_init_module

Annotated Snippet

static const struct file_operations hostaudio_fops = {
	.owner          = THIS_MODULE,
	.read           = hostaudio_read,
	.write          = hostaudio_write,
	.poll           = hostaudio_poll,
	.unlocked_ioctl	= hostaudio_ioctl,
	.compat_ioctl	= compat_ptr_ioctl,
	.mmap           = NULL,
	.open           = hostaudio_open,
	.release        = hostaudio_release,
};

static const struct file_operations hostmixer_fops = {
	.owner          = THIS_MODULE,
	.unlocked_ioctl	= hostmixer_ioctl_mixdev,
	.open           = hostmixer_open_mixdev,
	.release        = hostmixer_release,
};

static struct {
	int dev_audio;
	int dev_mixer;
} module_data;

MODULE_AUTHOR("Steve Schmidtke");
MODULE_DESCRIPTION("UML Audio Relay");
MODULE_LICENSE("GPL");

static int __init hostaudio_init_module(void)
{
	kernel_param_lock(THIS_MODULE);
	printk(KERN_INFO "UML Audio Relay (host dsp = %s, host mixer = %s)\n",
	       dsp, mixer);
	kernel_param_unlock(THIS_MODULE);

	module_data.dev_audio = register_sound_dsp(&hostaudio_fops, -1);
	if (module_data.dev_audio < 0) {
		printk(KERN_ERR "hostaudio: couldn't register DSP device!\n");
		return -ENODEV;
	}

	module_data.dev_mixer = register_sound_mixer(&hostmixer_fops, -1);
	if (module_data.dev_mixer < 0) {
		printk(KERN_ERR "hostmixer: couldn't register mixer "
		       "device!\n");
		unregister_sound_dsp(module_data.dev_audio);
		return -ENODEV;
	}

	return 0;
}

static void __exit hostaudio_cleanup_module (void)
{
	unregister_sound_mixer(module_data.dev_mixer);
	unregister_sound_dsp(module_data.dev_audio);
}

module_init(hostaudio_init_module);
module_exit(hostaudio_cleanup_module);

Annotation

• Immediate include surface: `linux/fs.h`, `linux/module.h`, `linux/slab.h`, `linux/sound.h`, `linux/soundcard.h`, `linux/mutex.h`, `linux/uaccess.h`, `init.h`.
• Detected declarations: `struct hostaudio_state`, `struct hostmixer_state`, `function set_dsp`, `function set_mixer`, `function hostaudio_read`, `function hostaudio_write`, `function hostaudio_poll`, `function hostaudio_ioctl`, `function hostaudio_open`, `function hostaudio_release`.
• Atlas domain: Architecture Layer / arch/um.
• 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.