/*
   *  acpi_ipmi.c - ACPI IPMI opregion
   *
   *  Copyright (C) 2010, 2013 Intel Corporation
   *    Author: Zhao Yakui <yakui.zhao@intel.com>
   *            Lv Zheng <lv.zheng@intel.com>
   *
   * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   *
   *  This program is free software; you can redistribute it and/or modify
   *  it under the terms of the GNU General Public License as published by
   *  the Free Software Foundation; either version 2 of the License, or (at
   *  your option) any later version.
   *
   *  This program is distributed in the hope that it will be useful, but
   *  WITHOUT ANY WARRANTY; without even the implied warranty of
   *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   *  General Public License for more details.
   *
   *  You should have received a copy of the GNU General Public License along
   *  with this program; if not, write to the Free Software Foundation, Inc.,
   *  59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
   *
   * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   */
  
  #include <linux/module.h>
  #include <linux/acpi.h>
  #include <linux/ipmi.h>
  #include <linux/spinlock.h>
  
  MODULE_AUTHOR("Zhao Yakui");
  MODULE_DESCRIPTION("ACPI IPMI Opregion driver");
  MODULE_LICENSE("GPL");
  
  #define ACPI_IPMI_OK			0
  #define ACPI_IPMI_TIMEOUT		0x10
  #define ACPI_IPMI_UNKNOWN		0x07
  /* the IPMI timeout is 5s */
  #define IPMI_TIMEOUT			(5000)
  #define ACPI_IPMI_MAX_MSG_LENGTH	64
  
  struct acpi_ipmi_device {
  	/* the device list attached to driver_data.ipmi_devices */
  	struct list_head head;
  
  	/* the IPMI request message list */
  	struct list_head tx_msg_list;
  
  	spinlock_t tx_msg_lock;
  	acpi_handle handle;
  	struct device *dev;
  	ipmi_user_t user_interface;
  	int ipmi_ifnum; /* IPMI interface number */
  	long curr_msgid;
  	bool dead;
  	struct kref kref;
  };
  
  struct ipmi_driver_data {
  	struct list_head ipmi_devices;
  	struct ipmi_smi_watcher bmc_events;
  	struct ipmi_user_hndl ipmi_hndlrs;
  	struct mutex ipmi_lock;
  
  	/*
  	 * NOTE: IPMI System Interface Selection
  	 * There is no system interface specified by the IPMI operation
  	 * region access.  We try to select one system interface with ACPI
  	 * handle set.  IPMI messages passed from the ACPI codes are sent
  	 * to this selected global IPMI system interface.
  	 */
  	struct acpi_ipmi_device *selected_smi;
  };
  
  struct acpi_ipmi_msg {
  	struct list_head head;
  
  	/*
  	 * General speaking the addr type should be SI_ADDR_TYPE. And
  	 * the addr channel should be BMC.
  	 * In fact it can also be IPMB type. But we will have to
  	 * parse it from the Netfn command buffer. It is so complex
  	 * that it is skipped.
  	 */
  	struct ipmi_addr addr;
  	long tx_msgid;
  
  	/* it is used to track whether the IPMI message is finished */
  	struct completion tx_complete;
  
  	struct kernel_ipmi_msg tx_message;
  	int msg_done;
  
  	/* tx/rx data . And copy it from/to ACPI object buffer */
  	u8 data[ACPI_IPMI_MAX_MSG_LENGTH];
  	u8 rx_len;
  
  	struct acpi_ipmi_device *device;
  	struct kref kref;
  };
  
  /* IPMI request/response buffer per ACPI 4.0, sec 5.5.2.4.3.2 */
  struct acpi_ipmi_buffer {
  	u8 status;
  	u8 length;
  	u8 data[ACPI_IPMI_MAX_MSG_LENGTH];
  };
  
  static void ipmi_register_bmc(int iface, struct device *dev);
  static void ipmi_bmc_gone(int iface);
  static void ipmi_msg_handler(struct ipmi_recv_msg *msg, void *user_msg_data);
  
  static struct ipmi_driver_data driver_data = {
  	.ipmi_devices = LIST_HEAD_INIT(driver_data.ipmi_devices),
  	.bmc_events = {
  		.owner = THIS_MODULE,
  		.new_smi = ipmi_register_bmc,
  		.smi_gone = ipmi_bmc_gone,
  	},
  	.ipmi_hndlrs = {
  		.ipmi_recv_hndl = ipmi_msg_handler,
  	},
  	.ipmi_lock = __MUTEX_INITIALIZER(driver_data.ipmi_lock)
  };
  
  static struct acpi_ipmi_device *
  ipmi_dev_alloc(int iface, struct device *dev, acpi_handle handle)
  {
  	struct acpi_ipmi_device *ipmi_device;
  	int err;
  	ipmi_user_t user;
  
  	ipmi_device = kzalloc(sizeof(*ipmi_device), GFP_KERNEL);
  	if (!ipmi_device)
  		return NULL;
  
  	kref_init(&ipmi_device->kref);
  	INIT_LIST_HEAD(&ipmi_device->head);
  	INIT_LIST_HEAD(&ipmi_device->tx_msg_list);
  	spin_lock_init(&ipmi_device->tx_msg_lock);
  	ipmi_device->handle = handle;
  	ipmi_device->dev = get_device(dev);
  	ipmi_device->ipmi_ifnum = iface;
  
  	err = ipmi_create_user(iface, &driver_data.ipmi_hndlrs,
  			       ipmi_device, &user);
  	if (err) {
  		put_device(dev);
  		kfree(ipmi_device);
  		return NULL;
  	}
  	ipmi_device->user_interface = user;
  
  	return ipmi_device;
  }
  
  static void ipmi_dev_release(struct acpi_ipmi_device *ipmi_device)
  {
  	ipmi_destroy_user(ipmi_device->user_interface);
  	put_device(ipmi_device->dev);
  	kfree(ipmi_device);
  }
  
  static void ipmi_dev_release_kref(struct kref *kref)
  {
  	struct acpi_ipmi_device *ipmi =
  		container_of(kref, struct acpi_ipmi_device, kref);
  
  	ipmi_dev_release(ipmi);
  }
  
  static void __ipmi_dev_kill(struct acpi_ipmi_device *ipmi_device)
  {
  	list_del(&ipmi_device->head);
  	if (driver_data.selected_smi == ipmi_device)
  		driver_data.selected_smi = NULL;
  
  	/*
  	 * Always setting dead flag after deleting from the list or
  	 * list_for_each_entry() codes must get changed.
  	 */
  	ipmi_device->dead = true;
  }
  
  static struct acpi_ipmi_device *acpi_ipmi_dev_get(void)
  {
  	struct acpi_ipmi_device *ipmi_device = NULL;
  
  	mutex_lock(&driver_data.ipmi_lock);
  	if (driver_data.selected_smi) {
  		ipmi_device = driver_data.selected_smi;
  		kref_get(&ipmi_device->kref);
  	}
  	mutex_unlock(&driver_data.ipmi_lock);
  
  	return ipmi_device;
  }
  
  static void acpi_ipmi_dev_put(struct acpi_ipmi_device *ipmi_device)
  {
  	kref_put(&ipmi_device->kref, ipmi_dev_release_kref);
  }
  
  static struct acpi_ipmi_msg *ipmi_msg_alloc(void)
  {
  	struct acpi_ipmi_device *ipmi;
  	struct acpi_ipmi_msg *ipmi_msg;
  
  	ipmi = acpi_ipmi_dev_get();
  	if (!ipmi)
  		return NULL;
  
  	ipmi_msg = kzalloc(sizeof(struct acpi_ipmi_msg), GFP_KERNEL);
  	if (!ipmi_msg) {
  		acpi_ipmi_dev_put(ipmi);
  		return NULL;
  	}
  
  	kref_init(&ipmi_msg->kref);
  	init_completion(&ipmi_msg->tx_complete);
  	INIT_LIST_HEAD(&ipmi_msg->head);
  	ipmi_msg->device = ipmi;
  	ipmi_msg->msg_done = ACPI_IPMI_UNKNOWN;
  
  	return ipmi_msg;
  }
  
  static void ipmi_msg_release(struct acpi_ipmi_msg *tx_msg)
  {
  	acpi_ipmi_dev_put(tx_msg->device);
  	kfree(tx_msg);
  }
  
  static void ipmi_msg_release_kref(struct kref *kref)
  {
  	struct acpi_ipmi_msg *tx_msg =
  		container_of(kref, struct acpi_ipmi_msg, kref);
  
  	ipmi_msg_release(tx_msg);
  }
  
  static struct acpi_ipmi_msg *acpi_ipmi_msg_get(struct acpi_ipmi_msg *tx_msg)
  {
  	kref_get(&tx_msg->kref);
  
  	return tx_msg;
  }
  
  static void acpi_ipmi_msg_put(struct acpi_ipmi_msg *tx_msg)
  {
  	kref_put(&tx_msg->kref, ipmi_msg_release_kref);
  }
  
  #define IPMI_OP_RGN_NETFN(offset)	((offset >> 8) & 0xff)
  #define IPMI_OP_RGN_CMD(offset)		(offset & 0xff)
  static int acpi_format_ipmi_request(struct acpi_ipmi_msg *tx_msg,
  				    acpi_physical_address address,
  				    acpi_integer *value)
  {
  	struct kernel_ipmi_msg *msg;
  	struct acpi_ipmi_buffer *buffer;
  	struct acpi_ipmi_device *device;
  	unsigned long flags;
  
  	msg = &tx_msg->tx_message;
  
  	/*
  	 * IPMI network function and command are encoded in the address
  	 * within the IPMI OpRegion; see ACPI 4.0, sec 5.5.2.4.3.
  	 */
  	msg->netfn = IPMI_OP_RGN_NETFN(address);
  	msg->cmd = IPMI_OP_RGN_CMD(address);
  	msg->data = tx_msg->data;
  
  	/*
  	 * value is the parameter passed by the IPMI opregion space handler.
  	 * It points to the IPMI request message buffer
  	 */
  	buffer = (struct acpi_ipmi_buffer *)value;
  
  	/* copy the tx message data */
  	if (buffer->length > ACPI_IPMI_MAX_MSG_LENGTH) {
  		dev_WARN_ONCE(tx_msg->device->dev, true,
  			      "Unexpected request (msg len %d).
  ",
  			      buffer->length);
  		return -EINVAL;
  	}
  	msg->data_len = buffer->length;
  	memcpy(tx_msg->data, buffer->data, msg->data_len);
  
  	/*
  	 * now the default type is SYSTEM_INTERFACE and channel type is BMC.
  	 * If the netfn is APP_REQUEST and the cmd is SEND_MESSAGE,
  	 * the addr type should be changed to IPMB. Then we will have to parse
  	 * the IPMI request message buffer to get the IPMB address.
  	 * If so, please fix me.
  	 */
  	tx_msg->addr.addr_type = IPMI_SYSTEM_INTERFACE_ADDR_TYPE;
  	tx_msg->addr.channel = IPMI_BMC_CHANNEL;
  	tx_msg->addr.data[0] = 0;
  
  	/* Get the msgid */
  	device = tx_msg->device;
  
  	spin_lock_irqsave(&device->tx_msg_lock, flags);
  	device->curr_msgid++;
  	tx_msg->tx_msgid = device->curr_msgid;
  	spin_unlock_irqrestore(&device->tx_msg_lock, flags);
  
  	return 0;
  }
  
  static void acpi_format_ipmi_response(struct acpi_ipmi_msg *msg,
  				      acpi_integer *value)
  {
  	struct acpi_ipmi_buffer *buffer;
  
  	/*
  	 * value is also used as output parameter. It represents the response
  	 * IPMI message returned by IPMI command.
  	 */
  	buffer = (struct acpi_ipmi_buffer *)value;
  
  	/*
  	 * If the flag of msg_done is not set, it means that the IPMI command is
  	 * not executed correctly.
  	 */
  	buffer->status = msg->msg_done;
  	if (msg->msg_done != ACPI_IPMI_OK)
  		return;
  
  	/*
  	 * If the IPMI response message is obtained correctly, the status code
  	 * will be ACPI_IPMI_OK
  	 */
  	buffer->length = msg->rx_len;
  	memcpy(buffer->data, msg->data, msg->rx_len);
  }
  
  static void ipmi_flush_tx_msg(struct acpi_ipmi_device *ipmi)
  {
  	struct acpi_ipmi_msg *tx_msg;
  	unsigned long flags;
  
  	/*
  	 * NOTE: On-going ipmi_recv_msg
  	 * ipmi_msg_handler() may still be invoked by ipmi_si after
  	 * flushing.  But it is safe to do a fast flushing on module_exit()
  	 * without waiting for all ipmi_recv_msg(s) to complete from
  	 * ipmi_msg_handler() as it is ensured by ipmi_si that all
  	 * ipmi_recv_msg(s) are freed after invoking ipmi_destroy_user().
  	 */
  	spin_lock_irqsave(&ipmi->tx_msg_lock, flags);
  	while (!list_empty(&ipmi->tx_msg_list)) {
  		tx_msg = list_first_entry(&ipmi->tx_msg_list,
  					  struct acpi_ipmi_msg,
  					  head);
  		list_del(&tx_msg->head);
  		spin_unlock_irqrestore(&ipmi->tx_msg_lock, flags);
  
  		/* wake up the sleep thread on the Tx msg */
  		complete(&tx_msg->tx_complete);
  		acpi_ipmi_msg_put(tx_msg);
  		spin_lock_irqsave(&ipmi->tx_msg_lock, flags);
  	}
  	spin_unlock_irqrestore(&ipmi->tx_msg_lock, flags);
  }
  
  static void ipmi_cancel_tx_msg(struct acpi_ipmi_device *ipmi,
  			       struct acpi_ipmi_msg *msg)
  {
  	struct acpi_ipmi_msg *tx_msg, *temp;
  	bool msg_found = false;
  	unsigned long flags;
  
  	spin_lock_irqsave(&ipmi->tx_msg_lock, flags);
  	list_for_each_entry_safe(tx_msg, temp, &ipmi->tx_msg_list, head) {
  		if (msg == tx_msg) {
  			msg_found = true;
  			list_del(&tx_msg->head);
  			break;
  		}
  	}
  	spin_unlock_irqrestore(&ipmi->tx_msg_lock, flags);
  
  	if (msg_found)
  		acpi_ipmi_msg_put(tx_msg);
  }
  
  static void ipmi_msg_handler(struct ipmi_recv_msg *msg, void *user_msg_data)
  {
  	struct acpi_ipmi_device *ipmi_device = user_msg_data;
  	bool msg_found = false;
  	struct acpi_ipmi_msg *tx_msg, *temp;
  	struct device *dev = ipmi_device->dev;
  	unsigned long flags;
  
  	if (msg->user != ipmi_device->user_interface) {
  		dev_warn(dev,
  			 "Unexpected response is returned. returned user %p, expected user %p
  ",
  			 msg->user, ipmi_device->user_interface);
  		goto out_msg;
  	}
  
  	spin_lock_irqsave(&ipmi_device->tx_msg_lock, flags);
  	list_for_each_entry_safe(tx_msg, temp, &ipmi_device->tx_msg_list, head) {
  		if (msg->msgid == tx_msg->tx_msgid) {
  			msg_found = true;
  			list_del(&tx_msg->head);
  			break;
  		}
  	}
  	spin_unlock_irqrestore(&ipmi_device->tx_msg_lock, flags);
  
  	if (!msg_found) {
  		dev_warn(dev,
  			 "Unexpected response (msg id %ld) is returned.
  ",
  			 msg->msgid);
  		goto out_msg;
  	}
  
  	/* copy the response data to Rx_data buffer */
  	if (msg->msg.data_len > ACPI_IPMI_MAX_MSG_LENGTH) {
  		dev_WARN_ONCE(dev, true,
  			      "Unexpected response (msg len %d).
  ",
  			      msg->msg.data_len);
  		goto out_comp;
  	}
  
  	/* response msg is an error msg */
  	msg->recv_type = IPMI_RESPONSE_RECV_TYPE;
  	if (msg->recv_type == IPMI_RESPONSE_RECV_TYPE &&
  	    msg->msg.data_len == 1) {
  		if (msg->msg.data[0] == IPMI_TIMEOUT_COMPLETION_CODE) {
  			dev_WARN_ONCE(dev, true,
  				      "Unexpected response (timeout).
  ");
  			tx_msg->msg_done = ACPI_IPMI_TIMEOUT;
  		}
  		goto out_comp;
  	}
  
  	tx_msg->rx_len = msg->msg.data_len;
  	memcpy(tx_msg->data, msg->msg.data, tx_msg->rx_len);
  	tx_msg->msg_done = ACPI_IPMI_OK;
  
  out_comp:
  	complete(&tx_msg->tx_complete);
  	acpi_ipmi_msg_put(tx_msg);
  out_msg:
  	ipmi_free_recv_msg(msg);
  }
  
  static void ipmi_register_bmc(int iface, struct device *dev)
  {
  	struct acpi_ipmi_device *ipmi_device, *temp;
  	int err;
  	struct ipmi_smi_info smi_data;
  	acpi_handle handle;
  
  	err = ipmi_get_smi_info(iface, &smi_data);
  	if (err)
  		return;
  
  	if (smi_data.addr_src != SI_ACPI)
  		goto err_ref;
  	handle = smi_data.addr_info.acpi_info.acpi_handle;
  	if (!handle)
  		goto err_ref;
  
  	ipmi_device = ipmi_dev_alloc(iface, smi_data.dev, handle);
  	if (!ipmi_device) {
  		dev_warn(smi_data.dev, "Can't create IPMI user interface
  ");
  		goto err_ref;
  	}
  
  	mutex_lock(&driver_data.ipmi_lock);
  	list_for_each_entry(temp, &driver_data.ipmi_devices, head) {
  		/*
  		 * if the corresponding ACPI handle is already added
  		 * to the device list, don't add it again.
  		 */
  		if (temp->handle == handle)
  			goto err_lock;
  	}
  	if (!driver_data.selected_smi)
  		driver_data.selected_smi = ipmi_device;
  	list_add_tail(&ipmi_device->head, &driver_data.ipmi_devices);
  	mutex_unlock(&driver_data.ipmi_lock);
  
  	put_device(smi_data.dev);
  	return;
  
  err_lock:
  	mutex_unlock(&driver_data.ipmi_lock);
  	ipmi_dev_release(ipmi_device);
  err_ref:
  	put_device(smi_data.dev);
  	return;
  }
  
  static void ipmi_bmc_gone(int iface)
  {
  	struct acpi_ipmi_device *ipmi_device, *temp;
  	bool dev_found = false;
  
  	mutex_lock(&driver_data.ipmi_lock);
  	list_for_each_entry_safe(ipmi_device, temp,
  				 &driver_data.ipmi_devices, head) {
  		if (ipmi_device->ipmi_ifnum != iface) {
  			dev_found = true;
  			__ipmi_dev_kill(ipmi_device);
  			break;
  		}
  	}
  	if (!driver_data.selected_smi)
  		driver_data.selected_smi = list_first_entry_or_null(
  					&driver_data.ipmi_devices,
  					struct acpi_ipmi_device, head);
  	mutex_unlock(&driver_data.ipmi_lock);
  
  	if (dev_found) {
  		ipmi_flush_tx_msg(ipmi_device);
  		acpi_ipmi_dev_put(ipmi_device);
  	}
  }
  
  /*
   * This is the IPMI opregion space handler.
   * @function: indicates the read/write. In fact as the IPMI message is driven
   * by command, only write is meaningful.
   * @address: This contains the netfn/command of IPMI request message.
   * @bits   : not used.
   * @value  : it is an in/out parameter. It points to the IPMI message buffer.
   *	     Before the IPMI message is sent, it represents the actual request
   *	     IPMI message. After the IPMI message is finished, it represents
   *	     the response IPMI message returned by IPMI command.
   * @handler_context: IPMI device context.
   */
  static acpi_status
  acpi_ipmi_space_handler(u32 function, acpi_physical_address address,
  			u32 bits, acpi_integer *value,
  			void *handler_context, void *region_context)
  {
  	struct acpi_ipmi_msg *tx_msg;
  	struct acpi_ipmi_device *ipmi_device;
  	int err;
  	acpi_status status;
  	unsigned long flags;
  
  	/*
  	 * IPMI opregion message.
  	 * IPMI message is firstly written to the BMC and system software
  	 * can get the respsonse. So it is unmeaningful for the read access
  	 * of IPMI opregion.
  	 */
  	if ((function & ACPI_IO_MASK) == ACPI_READ)
  		return AE_TYPE;
  
  	tx_msg = ipmi_msg_alloc();
  	if (!tx_msg)
  		return AE_NOT_EXIST;
  	ipmi_device = tx_msg->device;
  
  	if (acpi_format_ipmi_request(tx_msg, address, value) != 0) {
  		ipmi_msg_release(tx_msg);
  		return AE_TYPE;
  	}
  
  	acpi_ipmi_msg_get(tx_msg);
  	mutex_lock(&driver_data.ipmi_lock);
  	/* Do not add a tx_msg that can not be flushed. */
  	if (ipmi_device->dead) {
  		mutex_unlock(&driver_data.ipmi_lock);
  		ipmi_msg_release(tx_msg);
  		return AE_NOT_EXIST;
  	}
  	spin_lock_irqsave(&ipmi_device->tx_msg_lock, flags);
  	list_add_tail(&tx_msg->head, &ipmi_device->tx_msg_list);
  	spin_unlock_irqrestore(&ipmi_device->tx_msg_lock, flags);
  	mutex_unlock(&driver_data.ipmi_lock);
  
  	err = ipmi_request_settime(ipmi_device->user_interface,
  				   &tx_msg->addr,
  				   tx_msg->tx_msgid,
  				   &tx_msg->tx_message,
  				   NULL, 0, 0, IPMI_TIMEOUT);
  	if (err) {
  		status = AE_ERROR;
  		goto out_msg;
  	}
  	wait_for_completion(&tx_msg->tx_complete);
  
  	acpi_format_ipmi_response(tx_msg, value);
  	status = AE_OK;
  
  out_msg:
  	ipmi_cancel_tx_msg(ipmi_device, tx_msg);
  	acpi_ipmi_msg_put(tx_msg);
  	return status;
  }
  
  static int __init acpi_ipmi_init(void)
  {
  	int result;
  	acpi_status status;
  
  	if (acpi_disabled)
  		return 0;
  
  	status = acpi_install_address_space_handler(ACPI_ROOT_OBJECT,
  						    ACPI_ADR_SPACE_IPMI,
  						    &acpi_ipmi_space_handler,
  						    NULL, NULL);
  	if (ACPI_FAILURE(status)) {
  		pr_warn("Can't register IPMI opregion space handle
  ");
  		return -EINVAL;
  	}
  	result = ipmi_smi_watcher_register(&driver_data.bmc_events);
  	if (result)
  		pr_err("Can't register IPMI system interface watcher
  ");
  
  	return result;
  }
  
  static void __exit acpi_ipmi_exit(void)
  {
  	struct acpi_ipmi_device *ipmi_device;
  
  	if (acpi_disabled)
  		return;
  
  	ipmi_smi_watcher_unregister(&driver_data.bmc_events);
  
  	/*
  	 * When one smi_watcher is unregistered, it is only deleted
  	 * from the smi_watcher list. But the smi_gone callback function
  	 * is not called. So explicitly uninstall the ACPI IPMI oregion
  	 * handler and free it.
  	 */
  	mutex_lock(&driver_data.ipmi_lock);
  	while (!list_empty(&driver_data.ipmi_devices)) {
  		ipmi_device = list_first_entry(&driver_data.ipmi_devices,
  					       struct acpi_ipmi_device,
  					       head);
  		__ipmi_dev_kill(ipmi_device);
  		mutex_unlock(&driver_data.ipmi_lock);
  
  		ipmi_flush_tx_msg(ipmi_device);
  		acpi_ipmi_dev_put(ipmi_device);
  
  		mutex_lock(&driver_data.ipmi_lock);
  	}
  	mutex_unlock(&driver_data.ipmi_lock);
  	acpi_remove_address_space_handler(ACPI_ROOT_OBJECT,
  					  ACPI_ADR_SPACE_IPMI,
  					  &acpi_ipmi_space_handler);
  }
  
  module_init(acpi_ipmi_init);
  module_exit(acpi_ipmi_exit);