drivers/acpi/acpi_dbg.c - third_party/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * ACPI AML interfacing support
  *
  * Copyright (C) 2015, Intel Corporation
  * Authors: Lv Zheng <lv.zheng@intel.com>
  */

 /* #define DEBUG */
 #define pr_fmt(fmt) "ACPI: AML: " fmt

 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/wait.h>
 #include <linux/poll.h>
 #include <linux/sched.h>
 #include <linux/kthread.h>
 #include <linux/proc_fs.h>
 #include <linux/debugfs.h>
 #include <linux/circ_buf.h>
 #include <linux/acpi.h>
 #include "internal.h"

 #define ACPI_AML_BUF_ALIGN	(sizeof (acpi_size))
 #define ACPI_AML_BUF_SIZE	PAGE_SIZE

 #define circ_count(circ) \
 	(CIRC_CNT((circ)->head, (circ)->tail, ACPI_AML_BUF_SIZE))
 #define circ_count_to_end(circ) \
 	(CIRC_CNT_TO_END((circ)->head, (circ)->tail, ACPI_AML_BUF_SIZE))
 #define circ_space(circ) \
 	(CIRC_SPACE((circ)->head, (circ)->tail, ACPI_AML_BUF_SIZE))
 #define circ_space_to_end(circ) \
 	(CIRC_SPACE_TO_END((circ)->head, (circ)->tail, ACPI_AML_BUF_SIZE))

 #define ACPI_AML_OPENED		0x0001
 #define ACPI_AML_CLOSED		0x0002
 #define ACPI_AML_IN_USER	0x0004 /* user space is writing cmd */
 #define ACPI_AML_IN_KERN	0x0008 /* kernel space is reading cmd */
 #define ACPI_AML_OUT_USER	0x0010 /* user space is reading log */
 #define ACPI_AML_OUT_KERN	0x0020 /* kernel space is writing log */
 #define ACPI_AML_USER		(ACPI_AML_IN_USER | ACPI_AML_OUT_USER)
 #define ACPI_AML_KERN		(ACPI_AML_IN_KERN | ACPI_AML_OUT_KERN)
 #define ACPI_AML_BUSY		(ACPI_AML_USER | ACPI_AML_KERN)
 #define ACPI_AML_OPEN		(ACPI_AML_OPENED | ACPI_AML_CLOSED)

 struct acpi_aml_io {
 	wait_queue_head_t wait;
 	unsigned long flags;
 	unsigned long users;
 	struct mutex lock;
 	struct task_struct *thread;
 	char out_buf[ACPI_AML_BUF_SIZE] __aligned(ACPI_AML_BUF_ALIGN);
 	struct circ_buf out_crc;
 	char in_buf[ACPI_AML_BUF_SIZE] __aligned(ACPI_AML_BUF_ALIGN);
 	struct circ_buf in_crc;
 	acpi_osd_exec_callback function;
 	void *context;
 	unsigned long usages;
 };

 static struct acpi_aml_io acpi_aml_io;
 static bool acpi_aml_initialized;
 static struct file *acpi_aml_active_reader;
 static struct dentry *acpi_aml_dentry;

 static inline bool __acpi_aml_running(void)
 {
 	return acpi_aml_io.thread ? true : false;
 }

 static inline bool __acpi_aml_access_ok(unsigned long flag)
 {
 	/*
 	 * The debugger interface is in opened state (OPENED && !CLOSED),
 	 * then it is allowed to access the debugger buffers from either
 	 * user space or the kernel space.
 	 * In addition, for the kernel space, only the debugger thread
 	 * (thread ID matched) is allowed to access.
 	 */
 	if (!(acpi_aml_io.flags & ACPI_AML_OPENED) ||
 	    (acpi_aml_io.flags & ACPI_AML_CLOSED) ||
 	    !__acpi_aml_running())
 		return false;
 	if ((flag & ACPI_AML_KERN) &&
 	    current != acpi_aml_io.thread)
 		return false;
 	return true;
 }

 static inline bool __acpi_aml_readable(struct circ_buf *circ, unsigned long flag)
 {
 	/*
 	 * Another read is not in progress and there is data in buffer
 	 * available for read.
 	 */
 	if (!(acpi_aml_io.flags & flag) && circ_count(circ))
 		return true;
 	return false;
 }

 static inline bool __acpi_aml_writable(struct circ_buf *circ, unsigned long flag)
 {
 	/*
 	 * Another write is not in progress and there is buffer space
 	 * available for write.
 	 */
 	if (!(acpi_aml_io.flags & flag) && circ_space(circ))
 		return true;
 	return false;
 }

 static inline bool __acpi_aml_busy(void)
 {
 	if (acpi_aml_io.flags & ACPI_AML_BUSY)
 		return true;
 	return false;
 }

 static inline bool __acpi_aml_opened(void)
 {
 	if (acpi_aml_io.flags & ACPI_AML_OPEN)
 		return true;
 	return false;
 }

 static inline bool __acpi_aml_used(void)
 {
 	return acpi_aml_io.usages ? true : false;
 }

 static inline bool acpi_aml_running(void)
 {
 	bool ret;

 	mutex_lock(&acpi_aml_io.lock);
 	ret = __acpi_aml_running();
 	mutex_unlock(&acpi_aml_io.lock);
 	return ret;
 }

 static bool acpi_aml_busy(void)
 {
 	bool ret;

 	mutex_lock(&acpi_aml_io.lock);
 	ret = __acpi_aml_busy();
 	mutex_unlock(&acpi_aml_io.lock);
 	return ret;
 }

 static bool acpi_aml_used(void)
 {
 	bool ret;

 	/*
 	 * The usage count is prepared to avoid race conditions between the
 	 * starts and the stops of the debugger thread.
 	 */
 	mutex_lock(&acpi_aml_io.lock);
 	ret = __acpi_aml_used();
 	mutex_unlock(&acpi_aml_io.lock);
 	return ret;
 }

 static bool acpi_aml_kern_readable(void)
 {
 	bool ret;

 	mutex_lock(&acpi_aml_io.lock);
 	ret = !__acpi_aml_access_ok(ACPI_AML_IN_KERN) ||
 	      __acpi_aml_readable(&acpi_aml_io.in_crc, ACPI_AML_IN_KERN);
 	mutex_unlock(&acpi_aml_io.lock);
 	return ret;
 }

 static bool acpi_aml_kern_writable(void)
 {
 	bool ret;

 	mutex_lock(&acpi_aml_io.lock);
 	ret = !__acpi_aml_access_ok(ACPI_AML_OUT_KERN) ||
 	      __acpi_aml_writable(&acpi_aml_io.out_crc, ACPI_AML_OUT_KERN);
 	mutex_unlock(&acpi_aml_io.lock);
 	return ret;
 }

 static bool acpi_aml_user_readable(void)
 {
 	bool ret;

 	mutex_lock(&acpi_aml_io.lock);
 	ret = !__acpi_aml_access_ok(ACPI_AML_OUT_USER) ||
 	      __acpi_aml_readable(&acpi_aml_io.out_crc, ACPI_AML_OUT_USER);
 	mutex_unlock(&acpi_aml_io.lock);
 	return ret;
 }

 static bool acpi_aml_user_writable(void)
 {
 	bool ret;

 	mutex_lock(&acpi_aml_io.lock);
 	ret = !__acpi_aml_access_ok(ACPI_AML_IN_USER) ||
 	      __acpi_aml_writable(&acpi_aml_io.in_crc, ACPI_AML_IN_USER);
 	mutex_unlock(&acpi_aml_io.lock);
 	return ret;
 }

 static int acpi_aml_lock_write(struct circ_buf *circ, unsigned long flag)
 {
 	int ret = 0;

 	mutex_lock(&acpi_aml_io.lock);
 	if (!__acpi_aml_access_ok(flag)) {
 		ret = -EFAULT;
 		goto out;
 	}
 	if (!__acpi_aml_writable(circ, flag)) {
 		ret = -EAGAIN;
 		goto out;
 	}
 	acpi_aml_io.flags |= flag;
 out:
 	mutex_unlock(&acpi_aml_io.lock);
 	return ret;
 }

 static int acpi_aml_lock_read(struct circ_buf *circ, unsigned long flag)
 {
 	int ret = 0;

 	mutex_lock(&acpi_aml_io.lock);
 	if (!__acpi_aml_access_ok(flag)) {
 		ret = -EFAULT;
 		goto out;
 	}
 	if (!__acpi_aml_readable(circ, flag)) {
 		ret = -EAGAIN;
 		goto out;
 	}
 	acpi_aml_io.flags |= flag;
 out:
 	mutex_unlock(&acpi_aml_io.lock);
 	return ret;
 }

 static void acpi_aml_unlock_fifo(unsigned long flag, bool wakeup)
 {
 	mutex_lock(&acpi_aml_io.lock);
 	acpi_aml_io.flags &= ~flag;
 	if (wakeup)
 		wake_up_interruptible(&acpi_aml_io.wait);
 	mutex_unlock(&acpi_aml_io.lock);
 }

 static int acpi_aml_write_kern(const char *buf, int len)
 {
 	int ret;
 	struct circ_buf *crc = &acpi_aml_io.out_crc;
 	int n;
 	char *p;

 	ret = acpi_aml_lock_write(crc, ACPI_AML_OUT_KERN);
 	if (ret < 0)
 		return ret;
 	/* sync tail before inserting logs */
 	smp_mb();
 	p = &crc->buf[crc->head];
 	n = min(len, circ_space_to_end(crc));
 	memcpy(p, buf, n);
 	/* sync head after inserting logs */
 	smp_wmb();
 	crc->head = (crc->head + n) & (ACPI_AML_BUF_SIZE - 1);
 	acpi_aml_unlock_fifo(ACPI_AML_OUT_KERN, true);
 	return n;
 }

 static int acpi_aml_readb_kern(void)
 {
 	int ret;
 	struct circ_buf *crc = &acpi_aml_io.in_crc;
 	char *p;

 	ret = acpi_aml_lock_read(crc, ACPI_AML_IN_KERN);
 	if (ret < 0)
 		return ret;
 	/* sync head before removing cmds */
 	smp_rmb();
 	p = &crc->buf[crc->tail];
 	ret = (int)*p;
 	/* sync tail before inserting cmds */
 	smp_mb();
 	crc->tail = (crc->tail + 1) & (ACPI_AML_BUF_SIZE - 1);
 	acpi_aml_unlock_fifo(ACPI_AML_IN_KERN, true);
 	return ret;
 }

 /*
  * acpi_aml_write_log() - Capture debugger output
  * @msg: the debugger output
  *
  * This function should be used to implement acpi_os_printf() to filter out
  * the debugger output and store the output into the debugger interface
  * buffer. Return the size of stored logs or errno.
  */
 static ssize_t acpi_aml_write_log(const char *msg)
 {
 	int ret = 0;
 	int count = 0, size = 0;

 	if (!acpi_aml_initialized)
 		return -ENODEV;
 	if (msg)
 		count = strlen(msg);
 	while (count > 0) {
 again:
 		ret = acpi_aml_write_kern(msg + size, count);
 		if (ret == -EAGAIN) {
 			ret = wait_event_interruptible(acpi_aml_io.wait,
 				acpi_aml_kern_writable());
 			/*
 			 * We need to retry when the condition
 			 * becomes true.
 			 */
 			if (ret == 0)
 				goto again;
 			break;
 		}
 		if (ret < 0)
 			break;
 		size += ret;
 		count -= ret;
 	}
 	return size > 0 ? size : ret;
 }

 /*
  * acpi_aml_read_cmd() - Capture debugger input
  * @msg: the debugger input
  * @size: the size of the debugger input
  *
  * This function should be used to implement acpi_os_get_line() to capture
  * the debugger input commands and store the input commands into the
  * debugger interface buffer. Return the size of stored commands or errno.
  */
 static ssize_t acpi_aml_read_cmd(char *msg, size_t count)
 {
 	int ret = 0;
 	int size = 0;

 	/*
 	 * This is ensured by the running fact of the debugger thread
 	 * unless a bug is introduced.
 	 */
 	BUG_ON(!acpi_aml_initialized);
 	while (count > 0) {
 again:
 		/*
 		 * Check each input byte to find the end of the command.
 		 */
 		ret = acpi_aml_readb_kern();
 		if (ret == -EAGAIN) {
 			ret = wait_event_interruptible(acpi_aml_io.wait,
 				acpi_aml_kern_readable());
 			/*
 			 * We need to retry when the condition becomes
 			 * true.
 			 */
 			if (ret == 0)
 				goto again;
 		}
 		if (ret < 0)
 			break;
 		*(msg + size) = (char)ret;
 		size++;
 		count--;
 		if (ret == '\n') {
 			/*
 			 * acpi_os_get_line() requires a zero terminated command
 			 * string.
 			 */
 			*(msg + size - 1) = '\0';
 			break;
 		}
 	}
 	return size > 0 ? size : ret;
 }

 static int acpi_aml_thread(void *unused)
 {
 	acpi_osd_exec_callback function = NULL;
 	void *context;

 	mutex_lock(&acpi_aml_io.lock);
 	if (acpi_aml_io.function) {
 		acpi_aml_io.usages++;
 		function = acpi_aml_io.function;
 		context = acpi_aml_io.context;
 	}
 	mutex_unlock(&acpi_aml_io.lock);

 	if (function)
 		function(context);

 	mutex_lock(&acpi_aml_io.lock);
 	acpi_aml_io.usages--;
 	if (!__acpi_aml_used()) {
 		acpi_aml_io.thread = NULL;
 		wake_up(&acpi_aml_io.wait);
 	}
 	mutex_unlock(&acpi_aml_io.lock);

 	return 0;
 }

 /*
  * acpi_aml_create_thread() - Create AML debugger thread
  * @function: the debugger thread callback
  * @context: the context to be passed to the debugger thread
  *
  * This function should be used to implement acpi_os_execute() which is
  * used by the ACPICA debugger to create the debugger thread.
  */
 static int acpi_aml_create_thread(acpi_osd_exec_callback function, void *context)
 {
 	struct task_struct *t;

 	mutex_lock(&acpi_aml_io.lock);
 	acpi_aml_io.function = function;
 	acpi_aml_io.context = context;
 	mutex_unlock(&acpi_aml_io.lock);

 	t = kthread_create(acpi_aml_thread, NULL, "aml");
 	if (IS_ERR(t)) {
 		pr_err("Failed to create AML debugger thread.\n");
 		return PTR_ERR(t);
 	}

 	mutex_lock(&acpi_aml_io.lock);
 	acpi_aml_io.thread = t;
 	acpi_set_debugger_thread_id((acpi_thread_id)(unsigned long)t);
 	wake_up_process(t);
 	mutex_unlock(&acpi_aml_io.lock);
 	return 0;
 }

 static int acpi_aml_wait_command_ready(bool single_step,
 				       char *buffer, size_t length)
 {
 	acpi_status status;

 	if (single_step)
 		acpi_os_printf("\n%1c ", ACPI_DEBUGGER_EXECUTE_PROMPT);
 	else
 		acpi_os_printf("\n%1c ", ACPI_DEBUGGER_COMMAND_PROMPT);

 	status = acpi_os_get_line(buffer, length, NULL);
 	if (ACPI_FAILURE(status))
 		return -EINVAL;
 	return 0;
 }

 static int acpi_aml_notify_command_complete(void)
 {
 	return 0;
 }

 static int acpi_aml_open(struct inode *inode, struct file *file)
 {
 	int ret = 0;
 	acpi_status status;

 	mutex_lock(&acpi_aml_io.lock);
 	/*
 	 * The debugger interface is being closed, no new user is allowed
 	 * during this period.
 	 */
 	if (acpi_aml_io.flags & ACPI_AML_CLOSED) {
 		ret = -EBUSY;
 		goto err_lock;
 	}
 	if ((file->f_flags & O_ACCMODE) != O_WRONLY) {
 		/*
 		 * Only one reader is allowed to initiate the debugger
 		 * thread.
 		 */
 		if (acpi_aml_active_reader) {
 			ret = -EBUSY;
 			goto err_lock;
 		} else {
 			pr_debug("Opening debugger reader.\n");
 			acpi_aml_active_reader = file;
 		}
 	} else {
 		/*
 		 * No writer is allowed unless the debugger thread is
 		 * ready.
 		 */
 		if (!(acpi_aml_io.flags & ACPI_AML_OPENED)) {
 			ret = -ENODEV;
 			goto err_lock;
 		}
 	}
 	if (acpi_aml_active_reader == file) {
 		pr_debug("Opening debugger interface.\n");
 		mutex_unlock(&acpi_aml_io.lock);

 		pr_debug("Initializing debugger thread.\n");
 		status = acpi_initialize_debugger();
 		if (ACPI_FAILURE(status)) {
 			pr_err("Failed to initialize debugger.\n");
 			ret = -EINVAL;
 			goto err_exit;
 		}
 		pr_debug("Debugger thread initialized.\n");

 		mutex_lock(&acpi_aml_io.lock);
 		acpi_aml_io.flags |= ACPI_AML_OPENED;
 		acpi_aml_io.out_crc.head = acpi_aml_io.out_crc.tail = 0;
 		acpi_aml_io.in_crc.head = acpi_aml_io.in_crc.tail = 0;
 		pr_debug("Debugger interface opened.\n");
 	}
 	acpi_aml_io.users++;
 err_lock:
 	if (ret < 0) {
 		if (acpi_aml_active_reader == file)
 			acpi_aml_active_reader = NULL;
 	}
 	mutex_unlock(&acpi_aml_io.lock);
 err_exit:
 	return ret;
 }

 static int acpi_aml_release(struct inode *inode, struct file *file)
 {
 	mutex_lock(&acpi_aml_io.lock);
 	acpi_aml_io.users--;
 	if (file == acpi_aml_active_reader) {
 		pr_debug("Closing debugger reader.\n");
 		acpi_aml_active_reader = NULL;

 		pr_debug("Closing debugger interface.\n");
 		acpi_aml_io.flags |= ACPI_AML_CLOSED;

 		/*
 		 * Wake up all user space/kernel space blocked
 		 * readers/writers.
 		 */
 		wake_up_interruptible(&acpi_aml_io.wait);
 		mutex_unlock(&acpi_aml_io.lock);
 		/*
 		 * Wait all user space/kernel space readers/writers to
 		 * stop so that ACPICA command loop of the debugger thread
 		 * should fail all its command line reads after this point.
 		 */
 		wait_event(acpi_aml_io.wait, !acpi_aml_busy());

 		/*
 		 * Then we try to terminate the debugger thread if it is
 		 * not terminated.
 		 */
 		pr_debug("Terminating debugger thread.\n");
 		acpi_terminate_debugger();
 		wait_event(acpi_aml_io.wait, !acpi_aml_used());
 		pr_debug("Debugger thread terminated.\n");

 		mutex_lock(&acpi_aml_io.lock);
 		acpi_aml_io.flags &= ~ACPI_AML_OPENED;
 	}
 	if (acpi_aml_io.users == 0) {
 		pr_debug("Debugger interface closed.\n");
 		acpi_aml_io.flags &= ~ACPI_AML_CLOSED;
 	}
 	mutex_unlock(&acpi_aml_io.lock);
 	return 0;
 }

 static int acpi_aml_read_user(char __user *buf, int len)
 {
 	int ret;
 	struct circ_buf *crc = &acpi_aml_io.out_crc;
 	int n;
 	char *p;

 	ret = acpi_aml_lock_read(crc, ACPI_AML_OUT_USER);
 	if (ret < 0)
 		return ret;
 	/* sync head before removing logs */
 	smp_rmb();
 	p = &crc->buf[crc->tail];
 	n = min(len, circ_count_to_end(crc));
 	if (copy_to_user(buf, p, n)) {
 		ret = -EFAULT;
 		goto out;
 	}
 	/* sync tail after removing logs */
 	smp_mb();
 	crc->tail = (crc->tail + n) & (ACPI_AML_BUF_SIZE - 1);
 	ret = n;
 out:
 	acpi_aml_unlock_fifo(ACPI_AML_OUT_USER, ret >= 0);
 	return ret;
 }

 static ssize_t acpi_aml_read(struct file *file, char __user *buf,
 			     size_t count, loff_t *ppos)
 {
 	int ret = 0;
 	int size = 0;

 	if (!count)
 		return 0;
 	if (!access_ok(buf, count))
 		return -EFAULT;

 	while (count > 0) {
 again:
 		ret = acpi_aml_read_user(buf + size, count);
 		if (ret == -EAGAIN) {
 			if (file->f_flags & O_NONBLOCK)
 				break;
 			else {
 				ret = wait_event_interruptible(acpi_aml_io.wait,
 					acpi_aml_user_readable());
 				/*
 				 * We need to retry when the condition
 				 * becomes true.
 				 */
 				if (ret == 0)
 					goto again;
 			}
 		}
 		if (ret < 0) {
 			if (!acpi_aml_running())
 				ret = 0;
 			break;
 		}
 		if (ret) {
 			size += ret;
 			count -= ret;
 			*ppos += ret;
 			break;
 		}
 	}
 	return size > 0 ? size : ret;
 }

 static int acpi_aml_write_user(const char __user *buf, int len)
 {
 	int ret;
 	struct circ_buf *crc = &acpi_aml_io.in_crc;
 	int n;
 	char *p;

 	ret = acpi_aml_lock_write(crc, ACPI_AML_IN_USER);
 	if (ret < 0)
 		return ret;
 	/* sync tail before inserting cmds */
 	smp_mb();
 	p = &crc->buf[crc->head];
 	n = min(len, circ_space_to_end(crc));
 	if (copy_from_user(p, buf, n)) {
 		ret = -EFAULT;
 		goto out;
 	}
 	/* sync head after inserting cmds */
 	smp_wmb();
 	crc->head = (crc->head + n) & (ACPI_AML_BUF_SIZE - 1);
 	ret = n;
 out:
 	acpi_aml_unlock_fifo(ACPI_AML_IN_USER, ret >= 0);
 	return n;
 }

 static ssize_t acpi_aml_write(struct file *file, const char __user *buf,
 			      size_t count, loff_t *ppos)
 {
 	int ret = 0;
 	int size = 0;

 	if (!count)
 		return 0;
 	if (!access_ok(buf, count))
 		return -EFAULT;

 	while (count > 0) {
 again:
 		ret = acpi_aml_write_user(buf + size, count);
 		if (ret == -EAGAIN) {
 			if (file->f_flags & O_NONBLOCK)
 				break;
 			else {
 				ret = wait_event_interruptible(acpi_aml_io.wait,
 					acpi_aml_user_writable());
 				/*
 				 * We need to retry when the condition
 				 * becomes true.
 				 */
 				if (ret == 0)
 					goto again;
 			}
 		}
 		if (ret < 0) {
 			if (!acpi_aml_running())
 				ret = 0;
 			break;
 		}
 		if (ret) {
 			size += ret;
 			count -= ret;
 			*ppos += ret;
 		}
 	}
 	return size > 0 ? size : ret;
 }

 static __poll_t acpi_aml_poll(struct file *file, poll_table *wait)
 {
 	__poll_t masks = 0;

 	poll_wait(file, &acpi_aml_io.wait, wait);
 	if (acpi_aml_user_readable())
 		masks |= EPOLLIN | EPOLLRDNORM;
 	if (acpi_aml_user_writable())
 		masks |= EPOLLOUT | EPOLLWRNORM;

 	return masks;
 }

 static const struct file_operations acpi_aml_operations = {
 	.read		= acpi_aml_read,
 	.write		= acpi_aml_write,
 	.poll		= acpi_aml_poll,
 	.open		= acpi_aml_open,
 	.release	= acpi_aml_release,
 	.llseek		= generic_file_llseek,
 };

 static const struct acpi_debugger_ops acpi_aml_debugger = {
 	.create_thread		 = acpi_aml_create_thread,
 	.read_cmd		 = acpi_aml_read_cmd,
 	.write_log		 = acpi_aml_write_log,
 	.wait_command_ready	 = acpi_aml_wait_command_ready,
 	.notify_command_complete = acpi_aml_notify_command_complete,
 };

 int __init acpi_aml_init(void)
 {
 	int ret;

 	if (acpi_disabled)
 		return -ENODEV;

 	/* Initialize AML IO interface */
 	mutex_init(&acpi_aml_io.lock);
 	init_waitqueue_head(&acpi_aml_io.wait);
 	acpi_aml_io.out_crc.buf = acpi_aml_io.out_buf;
 	acpi_aml_io.in_crc.buf = acpi_aml_io.in_buf;

 	acpi_aml_dentry = debugfs_create_file("acpidbg",
 					      S_IFREG | S_IRUGO | S_IWUSR,
 					      acpi_debugfs_dir, NULL,
 					      &acpi_aml_operations);

 	ret = acpi_register_debugger(THIS_MODULE, &acpi_aml_debugger);
 	if (ret) {
 		debugfs_remove(acpi_aml_dentry);
 		acpi_aml_dentry = NULL;
 		return ret;
 	}

 	acpi_aml_initialized = true;
 	return 0;
 }

 void __exit acpi_aml_exit(void)
 {
 	if (acpi_aml_initialized) {
 		acpi_unregister_debugger(&acpi_aml_debugger);
 		debugfs_remove(acpi_aml_dentry);
 		acpi_aml_dentry = NULL;
 		acpi_aml_initialized = false;
 	}
 }

 module_init(acpi_aml_init);
 module_exit(acpi_aml_exit);

 MODULE_AUTHOR("Lv Zheng");
 MODULE_DESCRIPTION("ACPI debugger userspace IO driver");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* ACPI AML interfacing support
	*
	* Copyright (C) 2015, Intel Corporation
	* Authors: Lv Zheng <lv.zheng@intel.com>
	*/

	/* #define DEBUG */
	#define pr_fmt(fmt) "ACPI: AML: " fmt

	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/wait.h>
	#include <linux/poll.h>
	#include <linux/sched.h>
	#include <linux/kthread.h>
	#include <linux/proc_fs.h>
	#include <linux/debugfs.h>
	#include <linux/circ_buf.h>
	#include <linux/acpi.h>
	#include "internal.h"

	#define ACPI_AML_BUF_ALIGN (sizeof (acpi_size))
	#define ACPI_AML_BUF_SIZE PAGE_SIZE

	#define circ_count(circ) \
	(CIRC_CNT((circ)->head, (circ)->tail, ACPI_AML_BUF_SIZE))
	#define circ_count_to_end(circ) \
	(CIRC_CNT_TO_END((circ)->head, (circ)->tail, ACPI_AML_BUF_SIZE))
	#define circ_space(circ) \
	(CIRC_SPACE((circ)->head, (circ)->tail, ACPI_AML_BUF_SIZE))
	#define circ_space_to_end(circ) \
	(CIRC_SPACE_TO_END((circ)->head, (circ)->tail, ACPI_AML_BUF_SIZE))

	#define ACPI_AML_OPENED 0x0001
	#define ACPI_AML_CLOSED 0x0002
	#define ACPI_AML_IN_USER 0x0004 /* user space is writing cmd */
	#define ACPI_AML_IN_KERN 0x0008 /* kernel space is reading cmd */
	#define ACPI_AML_OUT_USER 0x0010 /* user space is reading log */
	#define ACPI_AML_OUT_KERN 0x0020 /* kernel space is writing log */
	#define ACPI_AML_USER (ACPI_AML_IN_USER \| ACPI_AML_OUT_USER)
	#define ACPI_AML_KERN (ACPI_AML_IN_KERN \| ACPI_AML_OUT_KERN)
	#define ACPI_AML_BUSY (ACPI_AML_USER \| ACPI_AML_KERN)
	#define ACPI_AML_OPEN (ACPI_AML_OPENED \| ACPI_AML_CLOSED)

	struct acpi_aml_io {
	wait_queue_head_t wait;
	unsigned long flags;
	unsigned long users;
	struct mutex lock;
	struct task_struct *thread;
	char out_buf[ACPI_AML_BUF_SIZE] __aligned(ACPI_AML_BUF_ALIGN);
	struct circ_buf out_crc;
	char in_buf[ACPI_AML_BUF_SIZE] __aligned(ACPI_AML_BUF_ALIGN);
	struct circ_buf in_crc;
	acpi_osd_exec_callback function;
	void *context;
	unsigned long usages;
	};

	static struct acpi_aml_io acpi_aml_io;
	static bool acpi_aml_initialized;
	static struct file *acpi_aml_active_reader;
	static struct dentry *acpi_aml_dentry;

	static inline bool __acpi_aml_running(void)
	{
	return acpi_aml_io.thread ? true : false;
	}

	static inline bool __acpi_aml_access_ok(unsigned long flag)
	{
	/*
	* The debugger interface is in opened state (OPENED && !CLOSED),
	* then it is allowed to access the debugger buffers from either
	* user space or the kernel space.
	* In addition, for the kernel space, only the debugger thread
	* (thread ID matched) is allowed to access.
	*/
	if (!(acpi_aml_io.flags & ACPI_AML_OPENED) \|\|
	(acpi_aml_io.flags & ACPI_AML_CLOSED) \|\|
	!__acpi_aml_running())
	return false;
	if ((flag & ACPI_AML_KERN) &&
	current != acpi_aml_io.thread)
	return false;
	return true;
	}

	static inline bool __acpi_aml_readable(struct circ_buf *circ, unsigned long flag)
	{
	/*
	* Another read is not in progress and there is data in buffer
	* available for read.
	*/
	if (!(acpi_aml_io.flags & flag) && circ_count(circ))
	return true;
	return false;
	}

	static inline bool __acpi_aml_writable(struct circ_buf *circ, unsigned long flag)
	{
	/*
	* Another write is not in progress and there is buffer space
	* available for write.
	*/
	if (!(acpi_aml_io.flags & flag) && circ_space(circ))
	return true;
	return false;
	}

	static inline bool __acpi_aml_busy(void)
	{
	if (acpi_aml_io.flags & ACPI_AML_BUSY)
	return true;
	return false;
	}

	static inline bool __acpi_aml_opened(void)
	{
	if (acpi_aml_io.flags & ACPI_AML_OPEN)
	return true;
	return false;
	}

	static inline bool __acpi_aml_used(void)
	{
	return acpi_aml_io.usages ? true : false;
	}

	static inline bool acpi_aml_running(void)
	{
	bool ret;

	mutex_lock(&acpi_aml_io.lock);
	ret = __acpi_aml_running();
	mutex_unlock(&acpi_aml_io.lock);
	return ret;
	}

	static bool acpi_aml_busy(void)
	{
	bool ret;

	mutex_lock(&acpi_aml_io.lock);
	ret = __acpi_aml_busy();
	mutex_unlock(&acpi_aml_io.lock);
	return ret;
	}

	static bool acpi_aml_used(void)
	{
	bool ret;

	/*
	* The usage count is prepared to avoid race conditions between the
	* starts and the stops of the debugger thread.
	*/
	mutex_lock(&acpi_aml_io.lock);
	ret = __acpi_aml_used();
	mutex_unlock(&acpi_aml_io.lock);
	return ret;
	}

	static bool acpi_aml_kern_readable(void)
	{
	bool ret;

	mutex_lock(&acpi_aml_io.lock);
	ret = !__acpi_aml_access_ok(ACPI_AML_IN_KERN) \|\|
	__acpi_aml_readable(&acpi_aml_io.in_crc, ACPI_AML_IN_KERN);
	mutex_unlock(&acpi_aml_io.lock);
	return ret;
	}

	static bool acpi_aml_kern_writable(void)
	{
	bool ret;

	mutex_lock(&acpi_aml_io.lock);
	ret = !__acpi_aml_access_ok(ACPI_AML_OUT_KERN) \|\|
	__acpi_aml_writable(&acpi_aml_io.out_crc, ACPI_AML_OUT_KERN);
	mutex_unlock(&acpi_aml_io.lock);
	return ret;
	}

	static bool acpi_aml_user_readable(void)
	{
	bool ret;

	mutex_lock(&acpi_aml_io.lock);
	ret = !__acpi_aml_access_ok(ACPI_AML_OUT_USER) \|\|
	__acpi_aml_readable(&acpi_aml_io.out_crc, ACPI_AML_OUT_USER);
	mutex_unlock(&acpi_aml_io.lock);
	return ret;
	}

	static bool acpi_aml_user_writable(void)
	{
	bool ret;

	mutex_lock(&acpi_aml_io.lock);
	ret = !__acpi_aml_access_ok(ACPI_AML_IN_USER) \|\|
	__acpi_aml_writable(&acpi_aml_io.in_crc, ACPI_AML_IN_USER);
	mutex_unlock(&acpi_aml_io.lock);
	return ret;
	}

	static int acpi_aml_lock_write(struct circ_buf *circ, unsigned long flag)
	{
	int ret = 0;

	mutex_lock(&acpi_aml_io.lock);
	if (!__acpi_aml_access_ok(flag)) {
	ret = -EFAULT;
	goto out;
	}
	if (!__acpi_aml_writable(circ, flag)) {
	ret = -EAGAIN;
	goto out;
	}
	acpi_aml_io.flags \|= flag;
	out:
	mutex_unlock(&acpi_aml_io.lock);
	return ret;
	}

	static int acpi_aml_lock_read(struct circ_buf *circ, unsigned long flag)
	{
	int ret = 0;

	mutex_lock(&acpi_aml_io.lock);
	if (!__acpi_aml_access_ok(flag)) {
	ret = -EFAULT;
	goto out;
	}
	if (!__acpi_aml_readable(circ, flag)) {
	ret = -EAGAIN;
	goto out;
	}
	acpi_aml_io.flags \|= flag;
	out:
	mutex_unlock(&acpi_aml_io.lock);
	return ret;
	}

	static void acpi_aml_unlock_fifo(unsigned long flag, bool wakeup)
	{
	mutex_lock(&acpi_aml_io.lock);
	acpi_aml_io.flags &= ~flag;
	if (wakeup)
	wake_up_interruptible(&acpi_aml_io.wait);
	mutex_unlock(&acpi_aml_io.lock);
	}

	static int acpi_aml_write_kern(const char *buf, int len)
	{
	int ret;
	struct circ_buf *crc = &acpi_aml_io.out_crc;
	int n;
	char *p;

	ret = acpi_aml_lock_write(crc, ACPI_AML_OUT_KERN);
	if (ret < 0)
	return ret;
	/* sync tail before inserting logs */
	smp_mb();
	p = &crc->buf[crc->head];
	n = min(len, circ_space_to_end(crc));
	memcpy(p, buf, n);
	/* sync head after inserting logs */
	smp_wmb();
	crc->head = (crc->head + n) & (ACPI_AML_BUF_SIZE - 1);
	acpi_aml_unlock_fifo(ACPI_AML_OUT_KERN, true);
	return n;
	}

	static int acpi_aml_readb_kern(void)
	{
	int ret;
	struct circ_buf *crc = &acpi_aml_io.in_crc;
	char *p;

	ret = acpi_aml_lock_read(crc, ACPI_AML_IN_KERN);
	if (ret < 0)
	return ret;
	/* sync head before removing cmds */
	smp_rmb();
	p = &crc->buf[crc->tail];
	ret = (int)*p;
	/* sync tail before inserting cmds */
	smp_mb();
	crc->tail = (crc->tail + 1) & (ACPI_AML_BUF_SIZE - 1);
	acpi_aml_unlock_fifo(ACPI_AML_IN_KERN, true);
	return ret;
	}

	/*
	* acpi_aml_write_log() - Capture debugger output
	* @msg: the debugger output
	*
	* This function should be used to implement acpi_os_printf() to filter out
	* the debugger output and store the output into the debugger interface
	* buffer. Return the size of stored logs or errno.
	*/
	static ssize_t acpi_aml_write_log(const char *msg)
	{
	int ret = 0;
	int count = 0, size = 0;

	if (!acpi_aml_initialized)
	return -ENODEV;
	if (msg)
	count = strlen(msg);
	while (count > 0) {
	again:
	ret = acpi_aml_write_kern(msg + size, count);
	if (ret == -EAGAIN) {
	ret = wait_event_interruptible(acpi_aml_io.wait,
	acpi_aml_kern_writable());
	/*
	* We need to retry when the condition
	* becomes true.
	*/
	if (ret == 0)
	goto again;
	break;
	}
	if (ret < 0)
	break;
	size += ret;
	count -= ret;
	}
	return size > 0 ? size : ret;
	}

	/*
	* acpi_aml_read_cmd() - Capture debugger input
	* @msg: the debugger input
	* @size: the size of the debugger input
	*
	* This function should be used to implement acpi_os_get_line() to capture
	* the debugger input commands and store the input commands into the
	* debugger interface buffer. Return the size of stored commands or errno.
	*/
	static ssize_t acpi_aml_read_cmd(char *msg, size_t count)
	{
	int ret = 0;
	int size = 0;

	/*
	* This is ensured by the running fact of the debugger thread
	* unless a bug is introduced.
	*/
	BUG_ON(!acpi_aml_initialized);
	while (count > 0) {
	again:
	/*
	* Check each input byte to find the end of the command.
	*/
	ret = acpi_aml_readb_kern();
	if (ret == -EAGAIN) {
	ret = wait_event_interruptible(acpi_aml_io.wait,
	acpi_aml_kern_readable());
	/*
	* We need to retry when the condition becomes
	* true.
	*/
	if (ret == 0)
	goto again;
	}
	if (ret < 0)
	break;
	*(msg + size) = (char)ret;
	size++;
	count--;
	if (ret == '\n') {
	/*
	* acpi_os_get_line() requires a zero terminated command
	* string.
	*/
	*(msg + size - 1) = '\0';
	break;
	}
	}
	return size > 0 ? size : ret;
	}

	static int acpi_aml_thread(void *unused)
	{
	acpi_osd_exec_callback function = NULL;
	void *context;

	mutex_lock(&acpi_aml_io.lock);
	if (acpi_aml_io.function) {
	acpi_aml_io.usages++;
	function = acpi_aml_io.function;
	context = acpi_aml_io.context;
	}
	mutex_unlock(&acpi_aml_io.lock);

	if (function)
	function(context);

	mutex_lock(&acpi_aml_io.lock);
	acpi_aml_io.usages--;
	if (!__acpi_aml_used()) {
	acpi_aml_io.thread = NULL;
	wake_up(&acpi_aml_io.wait);
	}
	mutex_unlock(&acpi_aml_io.lock);

	return 0;
	}

	/*
	* acpi_aml_create_thread() - Create AML debugger thread
	* @function: the debugger thread callback
	* @context: the context to be passed to the debugger thread
	*
	* This function should be used to implement acpi_os_execute() which is
	* used by the ACPICA debugger to create the debugger thread.
	*/
	static int acpi_aml_create_thread(acpi_osd_exec_callback function, void *context)
	{
	struct task_struct *t;

	mutex_lock(&acpi_aml_io.lock);
	acpi_aml_io.function = function;
	acpi_aml_io.context = context;
	mutex_unlock(&acpi_aml_io.lock);

	t = kthread_create(acpi_aml_thread, NULL, "aml");
	if (IS_ERR(t)) {
	pr_err("Failed to create AML debugger thread.\n");
	return PTR_ERR(t);
	}

	mutex_lock(&acpi_aml_io.lock);
	acpi_aml_io.thread = t;
	acpi_set_debugger_thread_id((acpi_thread_id)(unsigned long)t);
	wake_up_process(t);
	mutex_unlock(&acpi_aml_io.lock);
	return 0;
	}

	static int acpi_aml_wait_command_ready(bool single_step,
	char *buffer, size_t length)
	{
	acpi_status status;

	if (single_step)
	acpi_os_printf("\n%1c ", ACPI_DEBUGGER_EXECUTE_PROMPT);
	else
	acpi_os_printf("\n%1c ", ACPI_DEBUGGER_COMMAND_PROMPT);

	status = acpi_os_get_line(buffer, length, NULL);
	if (ACPI_FAILURE(status))
	return -EINVAL;
	return 0;
	}

	static int acpi_aml_notify_command_complete(void)
	{
	return 0;
	}

	static int acpi_aml_open(struct inode inode, struct file file)
	{
	int ret = 0;
	acpi_status status;

	mutex_lock(&acpi_aml_io.lock);
	/*
	* The debugger interface is being closed, no new user is allowed
	* during this period.
	*/
	if (acpi_aml_io.flags & ACPI_AML_CLOSED) {
	ret = -EBUSY;
	goto err_lock;
	}
	if ((file->f_flags & O_ACCMODE) != O_WRONLY) {
	/*
	* Only one reader is allowed to initiate the debugger
	* thread.
	*/
	if (acpi_aml_active_reader) {
	ret = -EBUSY;
	goto err_lock;
	} else {
	pr_debug("Opening debugger reader.\n");
	acpi_aml_active_reader = file;
	}
	} else {
	/*
	* No writer is allowed unless the debugger thread is
	* ready.
	*/
	if (!(acpi_aml_io.flags & ACPI_AML_OPENED)) {
	ret = -ENODEV;
	goto err_lock;
	}
	}
	if (acpi_aml_active_reader == file) {
	pr_debug("Opening debugger interface.\n");
	mutex_unlock(&acpi_aml_io.lock);

	pr_debug("Initializing debugger thread.\n");
	status = acpi_initialize_debugger();
	if (ACPI_FAILURE(status)) {
	pr_err("Failed to initialize debugger.\n");
	ret = -EINVAL;
	goto err_exit;
	}
	pr_debug("Debugger thread initialized.\n");

	mutex_lock(&acpi_aml_io.lock);
	acpi_aml_io.flags \|= ACPI_AML_OPENED;
	acpi_aml_io.out_crc.head = acpi_aml_io.out_crc.tail = 0;
	acpi_aml_io.in_crc.head = acpi_aml_io.in_crc.tail = 0;
	pr_debug("Debugger interface opened.\n");
	}
	acpi_aml_io.users++;
	err_lock:
	if (ret < 0) {
	if (acpi_aml_active_reader == file)
	acpi_aml_active_reader = NULL;
	}
	mutex_unlock(&acpi_aml_io.lock);
	err_exit:
	return ret;
	}

	static int acpi_aml_release(struct inode inode, struct file file)
	{
	mutex_lock(&acpi_aml_io.lock);
	acpi_aml_io.users--;
	if (file == acpi_aml_active_reader) {
	pr_debug("Closing debugger reader.\n");
	acpi_aml_active_reader = NULL;

	pr_debug("Closing debugger interface.\n");
	acpi_aml_io.flags \|= ACPI_AML_CLOSED;

	/*
	* Wake up all user space/kernel space blocked
	* readers/writers.
	*/
	wake_up_interruptible(&acpi_aml_io.wait);
	mutex_unlock(&acpi_aml_io.lock);
	/*
	* Wait all user space/kernel space readers/writers to
	* stop so that ACPICA command loop of the debugger thread
	* should fail all its command line reads after this point.
	*/
	wait_event(acpi_aml_io.wait, !acpi_aml_busy());

	/*
	* Then we try to terminate the debugger thread if it is
	* not terminated.
	*/
	pr_debug("Terminating debugger thread.\n");
	acpi_terminate_debugger();
	wait_event(acpi_aml_io.wait, !acpi_aml_used());
	pr_debug("Debugger thread terminated.\n");

	mutex_lock(&acpi_aml_io.lock);
	acpi_aml_io.flags &= ~ACPI_AML_OPENED;
	}
	if (acpi_aml_io.users == 0) {
	pr_debug("Debugger interface closed.\n");
	acpi_aml_io.flags &= ~ACPI_AML_CLOSED;
	}
	mutex_unlock(&acpi_aml_io.lock);
	return 0;
	}

	static int acpi_aml_read_user(char __user *buf, int len)
	{
	int ret;
	struct circ_buf *crc = &acpi_aml_io.out_crc;
	int n;
	char *p;

	ret = acpi_aml_lock_read(crc, ACPI_AML_OUT_USER);
	if (ret < 0)
	return ret;
	/* sync head before removing logs */
	smp_rmb();
	p = &crc->buf[crc->tail];
	n = min(len, circ_count_to_end(crc));
	if (copy_to_user(buf, p, n)) {
	ret = -EFAULT;
	goto out;
	}
	/* sync tail after removing logs */
	smp_mb();
	crc->tail = (crc->tail + n) & (ACPI_AML_BUF_SIZE - 1);
	ret = n;
	out:
	acpi_aml_unlock_fifo(ACPI_AML_OUT_USER, ret >= 0);
	return ret;
	}

	static ssize_t acpi_aml_read(struct file file, char __user buf,
	size_t count, loff_t *ppos)
	{
	int ret = 0;
	int size = 0;

	if (!count)
	return 0;
	if (!access_ok(buf, count))
	return -EFAULT;

	while (count > 0) {
	again:
	ret = acpi_aml_read_user(buf + size, count);
	if (ret == -EAGAIN) {
	if (file->f_flags & O_NONBLOCK)
	break;
	else {
	ret = wait_event_interruptible(acpi_aml_io.wait,
	acpi_aml_user_readable());
	/*
	* We need to retry when the condition
	* becomes true.
	*/
	if (ret == 0)
	goto again;
	}
	}
	if (ret < 0) {
	if (!acpi_aml_running())
	ret = 0;
	break;
	}
	if (ret) {
	size += ret;
	count -= ret;
	*ppos += ret;
	break;
	}
	}
	return size > 0 ? size : ret;
	}

	static int acpi_aml_write_user(const char __user *buf, int len)
	{
	int ret;
	struct circ_buf *crc = &acpi_aml_io.in_crc;
	int n;
	char *p;

	ret = acpi_aml_lock_write(crc, ACPI_AML_IN_USER);
	if (ret < 0)
	return ret;
	/* sync tail before inserting cmds */
	smp_mb();
	p = &crc->buf[crc->head];
	n = min(len, circ_space_to_end(crc));
	if (copy_from_user(p, buf, n)) {
	ret = -EFAULT;
	goto out;
	}
	/* sync head after inserting cmds */
	smp_wmb();
	crc->head = (crc->head + n) & (ACPI_AML_BUF_SIZE - 1);
	ret = n;
	out:
	acpi_aml_unlock_fifo(ACPI_AML_IN_USER, ret >= 0);
	return n;
	}

	static ssize_t acpi_aml_write(struct file file, const char __user buf,
	size_t count, loff_t *ppos)
	{
	int ret = 0;
	int size = 0;

	if (!count)
	return 0;
	if (!access_ok(buf, count))
	return -EFAULT;

	while (count > 0) {
	again:
	ret = acpi_aml_write_user(buf + size, count);
	if (ret == -EAGAIN) {
	if (file->f_flags & O_NONBLOCK)
	break;
	else {
	ret = wait_event_interruptible(acpi_aml_io.wait,
	acpi_aml_user_writable());
	/*
	* We need to retry when the condition
	* becomes true.
	*/
	if (ret == 0)
	goto again;
	}
	}
	if (ret < 0) {
	if (!acpi_aml_running())
	ret = 0;
	break;
	}
	if (ret) {
	size += ret;
	count -= ret;
	*ppos += ret;
	}
	}
	return size > 0 ? size : ret;
	}

	static __poll_t acpi_aml_poll(struct file file, poll_table wait)
	{
	__poll_t masks = 0;

	poll_wait(file, &acpi_aml_io.wait, wait);
	if (acpi_aml_user_readable())
	masks \|= EPOLLIN \| EPOLLRDNORM;
	if (acpi_aml_user_writable())
	masks \|= EPOLLOUT \| EPOLLWRNORM;

	return masks;
	}

	static const struct file_operations acpi_aml_operations = {
	.read = acpi_aml_read,
	.write = acpi_aml_write,
	.poll = acpi_aml_poll,
	.open = acpi_aml_open,
	.release = acpi_aml_release,
	.llseek = generic_file_llseek,
	};

	static const struct acpi_debugger_ops acpi_aml_debugger = {
	.create_thread = acpi_aml_create_thread,
	.read_cmd = acpi_aml_read_cmd,
	.write_log = acpi_aml_write_log,
	.wait_command_ready = acpi_aml_wait_command_ready,
	.notify_command_complete = acpi_aml_notify_command_complete,
	};

	int __init acpi_aml_init(void)
	{
	int ret;

	if (acpi_disabled)
	return -ENODEV;

	/* Initialize AML IO interface */
	mutex_init(&acpi_aml_io.lock);
	init_waitqueue_head(&acpi_aml_io.wait);
	acpi_aml_io.out_crc.buf = acpi_aml_io.out_buf;
	acpi_aml_io.in_crc.buf = acpi_aml_io.in_buf;

	acpi_aml_dentry = debugfs_create_file("acpidbg",
	S_IFREG \| S_IRUGO \| S_IWUSR,
	acpi_debugfs_dir, NULL,
	&acpi_aml_operations);

	ret = acpi_register_debugger(THIS_MODULE, &acpi_aml_debugger);
	if (ret) {
	debugfs_remove(acpi_aml_dentry);
	acpi_aml_dentry = NULL;
	return ret;
	}

	acpi_aml_initialized = true;
	return 0;
	}

	void __exit acpi_aml_exit(void)
	{
	if (acpi_aml_initialized) {
	acpi_unregister_debugger(&acpi_aml_debugger);
	debugfs_remove(acpi_aml_dentry);
	acpi_aml_dentry = NULL;
	acpi_aml_initialized = false;
	}
	}

	module_init(acpi_aml_init);
	module_exit(acpi_aml_exit);

	MODULE_AUTHOR("Lv Zheng");
	MODULE_DESCRIPTION("ACPI debugger userspace IO driver");
	MODULE_LICENSE("GPL");