Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 785 insertions, 0 deletions

diff --git a/drivers/acpi/acpi_dbg.c b/drivers/acpi/acpi_dbg.c
new file mode 100644
index 0000000000..d50261d05f
--- /dev/null
+++ b/drivers/acpi/acpi_dbg.c
@@ -0,0 +1,785 @@
+// 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_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,
+};
+
+static 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;
+}
+
+static 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");