drivers/misc/mei/interrupt.c - third_party/kernel - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (c) 2003-2018, Intel Corporation. All rights reserved.
  * Intel Management Engine Interface (Intel MEI) Linux driver
  */

 #include <linux/export.h>
 #include <linux/kthread.h>
 #include <linux/interrupt.h>
 #include <linux/fs.h>
 #include <linux/jiffies.h>
 #include <linux/slab.h>
 #include <linux/pm_runtime.h>

 #include <linux/mei.h>

 #include "mei_dev.h"
 #include "hbm.h"
 #include "client.h"


 /**
  * mei_irq_compl_handler - dispatch complete handlers
  *	for the completed callbacks
  *
  * @dev: mei device
  * @cmpl_list: list of completed cbs
  */
 void mei_irq_compl_handler(struct mei_device *dev, struct list_head *cmpl_list)
 {
 	struct mei_cl_cb *cb, *next;
 	struct mei_cl *cl;

 	list_for_each_entry_safe(cb, next, cmpl_list, list) {
 		cl = cb->cl;
 		list_del_init(&cb->list);

 		dev_dbg(dev->dev, "completing call back.\n");
 		mei_cl_complete(cl, cb);
 	}
 }
 EXPORT_SYMBOL_GPL(mei_irq_compl_handler);

 /**
  * mei_cl_hbm_equal - check if hbm is addressed to the client
  *
  * @cl: host client
  * @mei_hdr: header of mei client message
  *
  * Return: true if matches, false otherwise
  */
 static inline int mei_cl_hbm_equal(struct mei_cl *cl,
 			struct mei_msg_hdr *mei_hdr)
 {
 	return  mei_cl_host_addr(cl) == mei_hdr->host_addr &&
 		mei_cl_me_id(cl) == mei_hdr->me_addr;
 }

 /**
  * mei_irq_discard_msg  - discard received message
  *
  * @dev: mei device
  * @hdr: message header
  * @discard_len: the length of the message to discard (excluding header)
  */
 static void mei_irq_discard_msg(struct mei_device *dev, struct mei_msg_hdr *hdr,
 				size_t discard_len)
 {
 	if (hdr->dma_ring) {
 		mei_dma_ring_read(dev, NULL,
 				  hdr->extension[dev->rd_msg_hdr_count - 2]);
 		discard_len = 0;
 	}
 	/*
 	 * no need to check for size as it is guarantied
 	 * that length fits into rd_msg_buf
 	 */
 	mei_read_slots(dev, dev->rd_msg_buf, discard_len);
 	dev_dbg(dev->dev, "discarding message " MEI_HDR_FMT "\n",
 		MEI_HDR_PRM(hdr));
 }

 /**
  * mei_cl_irq_read_msg - process client message
  *
  * @cl: reading client
  * @mei_hdr: header of mei client message
  * @meta: extend meta header
  * @cmpl_list: completion list
  *
  * Return: always 0
  */
 static int mei_cl_irq_read_msg(struct mei_cl *cl,
 			       struct mei_msg_hdr *mei_hdr,
 			       struct mei_ext_meta_hdr *meta,
 			       struct list_head *cmpl_list)
 {
 	struct mei_device *dev = cl->dev;
 	struct mei_cl_cb *cb;

 	size_t buf_sz;
 	u32 length;
 	int ext_len;

 	length = mei_hdr->length;
 	ext_len = 0;
 	if (mei_hdr->extended) {
 		ext_len = sizeof(*meta) + mei_slots2data(meta->size);
 		length -= ext_len;
 	}

 	cb = list_first_entry_or_null(&cl->rd_pending, struct mei_cl_cb, list);
 	if (!cb) {
 		if (!mei_cl_is_fixed_address(cl)) {
 			cl_err(dev, cl, "pending read cb not found\n");
 			goto discard;
 		}
 		cb = mei_cl_alloc_cb(cl, mei_cl_mtu(cl), MEI_FOP_READ, cl->fp);
 		if (!cb)
 			goto discard;
 		list_add_tail(&cb->list, &cl->rd_pending);
 	}

 	if (mei_hdr->extended) {
 		struct mei_ext_hdr *ext;
 		struct mei_ext_hdr_vtag *vtag_hdr = NULL;

 		ext = mei_ext_begin(meta);
 		do {
 			switch (ext->type) {
 			case MEI_EXT_HDR_VTAG:
 				vtag_hdr = (struct mei_ext_hdr_vtag *)ext;
 				break;
 			case MEI_EXT_HDR_NONE:
 				fallthrough;
 			default:
 				cb->status = -EPROTO;
 				break;
 			}

 			ext = mei_ext_next(ext);
 		} while (!mei_ext_last(meta, ext));

 		if (!vtag_hdr) {
 			cl_dbg(dev, cl, "vtag not found in extended header.\n");
 			cb->status = -EPROTO;
 			goto discard;
 		}

 		cl_dbg(dev, cl, "vtag: %d\n", vtag_hdr->vtag);
 		if (cb->vtag && cb->vtag != vtag_hdr->vtag) {
 			cl_err(dev, cl, "mismatched tag: %d != %d\n",
 			       cb->vtag, vtag_hdr->vtag);
 			cb->status = -EPROTO;
 			goto discard;
 		}
 		cb->vtag = vtag_hdr->vtag;
 	}

 	if (!mei_cl_is_connected(cl)) {
 		cl_dbg(dev, cl, "not connected\n");
 		cb->status = -ENODEV;
 		goto discard;
 	}

 	if (mei_hdr->dma_ring)
 		length = mei_hdr->extension[mei_data2slots(ext_len)];

 	buf_sz = length + cb->buf_idx;
 	/* catch for integer overflow */
 	if (buf_sz < cb->buf_idx) {
 		cl_err(dev, cl, "message is too big len %d idx %zu\n",
 		       length, cb->buf_idx);
 		cb->status = -EMSGSIZE;
 		goto discard;
 	}

 	if (cb->buf.size < buf_sz) {
 		cl_dbg(dev, cl, "message overflow. size %zu len %d idx %zu\n",
 			cb->buf.size, length, cb->buf_idx);
 		cb->status = -EMSGSIZE;
 		goto discard;
 	}

 	if (mei_hdr->dma_ring) {
 		mei_dma_ring_read(dev, cb->buf.data + cb->buf_idx, length);
 		/*  for DMA read 0 length to generate interrupt to the device */
 		mei_read_slots(dev, cb->buf.data + cb->buf_idx, 0);
 	} else {
 		mei_read_slots(dev, cb->buf.data + cb->buf_idx, length);
 	}

 	cb->buf_idx += length;

 	if (mei_hdr->msg_complete) {
 		cl_dbg(dev, cl, "completed read length = %zu\n", cb->buf_idx);
 		list_move_tail(&cb->list, cmpl_list);
 	} else {
 		pm_runtime_mark_last_busy(dev->dev);
 		pm_request_autosuspend(dev->dev);
 	}

 	return 0;

 discard:
 	if (cb)
 		list_move_tail(&cb->list, cmpl_list);
 	mei_irq_discard_msg(dev, mei_hdr, length);
 	return 0;
 }

 /**
  * mei_cl_irq_disconnect_rsp - send disconnection response message
  *
  * @cl: client
  * @cb: callback block.
  * @cmpl_list: complete list.
  *
  * Return: 0, OK; otherwise, error.
  */
 static int mei_cl_irq_disconnect_rsp(struct mei_cl *cl, struct mei_cl_cb *cb,
 				     struct list_head *cmpl_list)
 {
 	struct mei_device *dev = cl->dev;
 	u32 msg_slots;
 	int slots;
 	int ret;

 	msg_slots = mei_hbm2slots(sizeof(struct hbm_client_connect_response));
 	slots = mei_hbuf_empty_slots(dev);
 	if (slots < 0)
 		return -EOVERFLOW;

 	if ((u32)slots < msg_slots)
 		return -EMSGSIZE;

 	ret = mei_hbm_cl_disconnect_rsp(dev, cl);
 	list_move_tail(&cb->list, cmpl_list);

 	return ret;
 }

 /**
  * mei_cl_irq_read - processes client read related operation from the
  *	interrupt thread context - request for flow control credits
  *
  * @cl: client
  * @cb: callback block.
  * @cmpl_list: complete list.
  *
  * Return: 0, OK; otherwise, error.
  */
 static int mei_cl_irq_read(struct mei_cl *cl, struct mei_cl_cb *cb,
 			   struct list_head *cmpl_list)
 {
 	struct mei_device *dev = cl->dev;
 	u32 msg_slots;
 	int slots;
 	int ret;

 	if (!list_empty(&cl->rd_pending))
 		return 0;

 	msg_slots = mei_hbm2slots(sizeof(struct hbm_flow_control));
 	slots = mei_hbuf_empty_slots(dev);
 	if (slots < 0)
 		return -EOVERFLOW;

 	if ((u32)slots < msg_slots)
 		return -EMSGSIZE;

 	ret = mei_hbm_cl_flow_control_req(dev, cl);
 	if (ret) {
 		cl->status = ret;
 		cb->buf_idx = 0;
 		list_move_tail(&cb->list, cmpl_list);
 		return ret;
 	}

 	pm_runtime_mark_last_busy(dev->dev);
 	pm_request_autosuspend(dev->dev);

 	list_move_tail(&cb->list, &cl->rd_pending);

 	return 0;
 }

 static inline bool hdr_is_hbm(struct mei_msg_hdr *mei_hdr)
 {
 	return mei_hdr->host_addr == 0 && mei_hdr->me_addr == 0;
 }

 static inline bool hdr_is_fixed(struct mei_msg_hdr *mei_hdr)
 {
 	return mei_hdr->host_addr == 0 && mei_hdr->me_addr != 0;
 }

 static inline int hdr_is_valid(u32 msg_hdr)
 {
 	struct mei_msg_hdr *mei_hdr;
 	u32 expected_len = 0;

 	mei_hdr = (struct mei_msg_hdr *)&msg_hdr;
 	if (!msg_hdr || mei_hdr->reserved)
 		return -EBADMSG;

 	if (mei_hdr->dma_ring)
 		expected_len += MEI_SLOT_SIZE;
 	if (mei_hdr->extended)
 		expected_len += MEI_SLOT_SIZE;
 	if (mei_hdr->length < expected_len)
 		return -EBADMSG;

 	return 0;
 }

 /**
  * mei_irq_read_handler - bottom half read routine after ISR to
  * handle the read processing.
  *
  * @dev: the device structure
  * @cmpl_list: An instance of our list structure
  * @slots: slots to read.
  *
  * Return: 0 on success, <0 on failure.
  */
 int mei_irq_read_handler(struct mei_device *dev,
 			 struct list_head *cmpl_list, s32 *slots)
 {
 	struct mei_msg_hdr *mei_hdr;
 	struct mei_ext_meta_hdr *meta_hdr = NULL;
 	struct mei_cl *cl;
 	int ret;
 	u32 hdr_size_left;
 	u32 hdr_size_ext;
 	int i;
 	int ext_hdr_end;

 	if (!dev->rd_msg_hdr[0]) {
 		dev->rd_msg_hdr[0] = mei_read_hdr(dev);
 		dev->rd_msg_hdr_count = 1;
 		(*slots)--;
 		dev_dbg(dev->dev, "slots =%08x.\n", *slots);

 		ret = hdr_is_valid(dev->rd_msg_hdr[0]);
 		if (ret) {
 			dev_err(dev->dev, "corrupted message header 0x%08X\n",
 				dev->rd_msg_hdr[0]);
 			goto end;
 		}
 	}

 	mei_hdr = (struct mei_msg_hdr *)dev->rd_msg_hdr;
 	dev_dbg(dev->dev, MEI_HDR_FMT, MEI_HDR_PRM(mei_hdr));

 	if (mei_slots2data(*slots) < mei_hdr->length) {
 		dev_err(dev->dev, "less data available than length=%08x.\n",
 				*slots);
 		/* we can't read the message */
 		ret = -ENODATA;
 		goto end;
 	}

 	ext_hdr_end = 1;
 	hdr_size_left = mei_hdr->length;

 	if (mei_hdr->extended) {
 		if (!dev->rd_msg_hdr[1]) {
 			dev->rd_msg_hdr[1] = mei_read_hdr(dev);
 			dev->rd_msg_hdr_count++;
 			(*slots)--;
 			dev_dbg(dev->dev, "extended header is %08x\n", dev->rd_msg_hdr[1]);
 		}
 		meta_hdr = ((struct mei_ext_meta_hdr *)&dev->rd_msg_hdr[1]);
 		if (check_add_overflow((u32)sizeof(*meta_hdr),
 				       mei_slots2data(meta_hdr->size),
 				       &hdr_size_ext)) {
 			dev_err(dev->dev, "extended message size too big %d\n",
 				meta_hdr->size);
 			return -EBADMSG;
 		}
 		if (hdr_size_left < hdr_size_ext) {
 			dev_err(dev->dev, "corrupted message header len %d\n",
 				mei_hdr->length);
 			return -EBADMSG;
 		}
 		hdr_size_left -= hdr_size_ext;

 		ext_hdr_end = meta_hdr->size + 2;
 		for (i = dev->rd_msg_hdr_count; i < ext_hdr_end; i++) {
 			dev->rd_msg_hdr[i] = mei_read_hdr(dev);
 			dev_dbg(dev->dev, "extended header %d is %08x\n", i,
 				dev->rd_msg_hdr[i]);
 			dev->rd_msg_hdr_count++;
 			(*slots)--;
 		}
 	}

 	if (mei_hdr->dma_ring) {
 		if (hdr_size_left != sizeof(dev->rd_msg_hdr[ext_hdr_end])) {
 			dev_err(dev->dev, "corrupted message header len %d\n",
 				mei_hdr->length);
 			return -EBADMSG;
 		}

 		dev->rd_msg_hdr[ext_hdr_end] = mei_read_hdr(dev);
 		dev->rd_msg_hdr_count++;
 		(*slots)--;
 		mei_hdr->length -= sizeof(dev->rd_msg_hdr[ext_hdr_end]);
 	}

 	/*  HBM message */
 	if (hdr_is_hbm(mei_hdr)) {
 		ret = mei_hbm_dispatch(dev, mei_hdr);
 		if (ret) {
 			dev_dbg(dev->dev, "mei_hbm_dispatch failed ret = %d\n",
 					ret);
 			goto end;
 		}
 		goto reset_slots;
 	}

 	/* find recipient cl */
 	list_for_each_entry(cl, &dev->file_list, link) {
 		if (mei_cl_hbm_equal(cl, mei_hdr)) {
 			cl_dbg(dev, cl, "got a message\n");
 			ret = mei_cl_irq_read_msg(cl, mei_hdr, meta_hdr, cmpl_list);
 			goto reset_slots;
 		}
 	}

 	/* if no recipient cl was found we assume corrupted header */
 	/* A message for not connected fixed address clients
 	 * should be silently discarded
 	 * On power down client may be force cleaned,
 	 * silently discard such messages
 	 */
 	if (hdr_is_fixed(mei_hdr) ||
 	    dev->dev_state == MEI_DEV_POWER_DOWN) {
 		mei_irq_discard_msg(dev, mei_hdr, mei_hdr->length);
 		ret = 0;
 		goto reset_slots;
 	}
 	dev_err(dev->dev, "no destination client found 0x%08X\n", dev->rd_msg_hdr[0]);
 	ret = -EBADMSG;
 	goto end;

 reset_slots:
 	/* reset the number of slots and header */
 	memset(dev->rd_msg_hdr, 0, sizeof(dev->rd_msg_hdr));
 	dev->rd_msg_hdr_count = 0;
 	*slots = mei_count_full_read_slots(dev);
 	if (*slots == -EOVERFLOW) {
 		/* overflow - reset */
 		dev_err(dev->dev, "resetting due to slots overflow.\n");
 		/* set the event since message has been read */
 		ret = -ERANGE;
 		goto end;
 	}
 end:
 	return ret;
 }
 EXPORT_SYMBOL_GPL(mei_irq_read_handler);


 /**
  * mei_irq_write_handler -  dispatch write requests
  *  after irq received
  *
  * @dev: the device structure
  * @cmpl_list: An instance of our list structure
  *
  * Return: 0 on success, <0 on failure.
  */
 int mei_irq_write_handler(struct mei_device *dev, struct list_head *cmpl_list)
 {

 	struct mei_cl *cl;
 	struct mei_cl_cb *cb, *next;
 	s32 slots;
 	int ret;


 	if (!mei_hbuf_acquire(dev))
 		return 0;

 	slots = mei_hbuf_empty_slots(dev);
 	if (slots < 0)
 		return -EOVERFLOW;

 	if (slots == 0)
 		return -EMSGSIZE;

 	/* complete all waiting for write CB */
 	dev_dbg(dev->dev, "complete all waiting for write cb.\n");

 	list_for_each_entry_safe(cb, next, &dev->write_waiting_list, list) {
 		cl = cb->cl;

 		cl->status = 0;
 		cl_dbg(dev, cl, "MEI WRITE COMPLETE\n");
 		cl->writing_state = MEI_WRITE_COMPLETE;
 		list_move_tail(&cb->list, cmpl_list);
 	}

 	/* complete control write list CB */
 	dev_dbg(dev->dev, "complete control write list cb.\n");
 	list_for_each_entry_safe(cb, next, &dev->ctrl_wr_list, list) {
 		cl = cb->cl;
 		switch (cb->fop_type) {
 		case MEI_FOP_DISCONNECT:
 			/* send disconnect message */
 			ret = mei_cl_irq_disconnect(cl, cb, cmpl_list);
 			if (ret)
 				return ret;

 			break;
 		case MEI_FOP_READ:
 			/* send flow control message */
 			ret = mei_cl_irq_read(cl, cb, cmpl_list);
 			if (ret)
 				return ret;

 			break;
 		case MEI_FOP_CONNECT:
 			/* connect message */
 			ret = mei_cl_irq_connect(cl, cb, cmpl_list);
 			if (ret)
 				return ret;

 			break;
 		case MEI_FOP_DISCONNECT_RSP:
 			/* send disconnect resp */
 			ret = mei_cl_irq_disconnect_rsp(cl, cb, cmpl_list);
 			if (ret)
 				return ret;
 			break;

 		case MEI_FOP_NOTIFY_START:
 		case MEI_FOP_NOTIFY_STOP:
 			ret = mei_cl_irq_notify(cl, cb, cmpl_list);
 			if (ret)
 				return ret;
 			break;
 		case MEI_FOP_DMA_MAP:
 			ret = mei_cl_irq_dma_map(cl, cb, cmpl_list);
 			if (ret)
 				return ret;
 			break;
 		case MEI_FOP_DMA_UNMAP:
 			ret = mei_cl_irq_dma_unmap(cl, cb, cmpl_list);
 			if (ret)
 				return ret;
 			break;
 		default:
 			BUG();
 		}

 	}
 	/* complete  write list CB */
 	dev_dbg(dev->dev, "complete write list cb.\n");
 	list_for_each_entry_safe(cb, next, &dev->write_list, list) {
 		cl = cb->cl;
 		ret = mei_cl_irq_write(cl, cb, cmpl_list);
 		if (ret)
 			return ret;
 	}
 	return 0;
 }
 EXPORT_SYMBOL_GPL(mei_irq_write_handler);


 /**
  * mei_connect_timeout  - connect/disconnect timeouts
  *
  * @cl: host client
  */
 static void mei_connect_timeout(struct mei_cl *cl)
 {
 	struct mei_device *dev = cl->dev;

 	if (cl->state == MEI_FILE_CONNECTING) {
 		if (dev->hbm_f_dot_supported) {
 			cl->state = MEI_FILE_DISCONNECT_REQUIRED;
 			wake_up(&cl->wait);
 			return;
 		}
 	}
 	mei_reset(dev);
 }

 #define MEI_STALL_TIMER_FREQ (2 * HZ)
 /**
  * mei_schedule_stall_timer - re-arm stall_timer work
  *
  * Schedule stall timer
  *
  * @dev: the device structure
  */
 void mei_schedule_stall_timer(struct mei_device *dev)
 {
 	schedule_delayed_work(&dev->timer_work, MEI_STALL_TIMER_FREQ);
 }

 /**
  * mei_timer - timer function.
  *
  * @work: pointer to the work_struct structure
  *
  */
 void mei_timer(struct work_struct *work)
 {
 	struct mei_cl *cl;
 	struct mei_device *dev = container_of(work,
 					struct mei_device, timer_work.work);
 	bool reschedule_timer = false;

 	mutex_lock(&dev->device_lock);

 	/* Catch interrupt stalls during HBM init handshake */
 	if (dev->dev_state == MEI_DEV_INIT_CLIENTS &&
 	    dev->hbm_state != MEI_HBM_IDLE) {

 		if (dev->init_clients_timer) {
 			if (--dev->init_clients_timer == 0) {
 				dev_err(dev->dev, "timer: init clients timeout hbm_state = %d.\n",
 					dev->hbm_state);
 				mei_reset(dev);
 				goto out;
 			}
 			reschedule_timer = true;
 		}
 	}

 	if (dev->dev_state != MEI_DEV_ENABLED)
 		goto out;

 	/*** connect/disconnect timeouts ***/
 	list_for_each_entry(cl, &dev->file_list, link) {
 		if (cl->timer_count) {
 			if (--cl->timer_count == 0) {
 				dev_err(dev->dev, "timer: connect/disconnect timeout.\n");
 				mei_connect_timeout(cl);
 				goto out;
 			}
 			reschedule_timer = true;
 		}
 	}

 out:
 	if (dev->dev_state != MEI_DEV_DISABLED && reschedule_timer)
 		mei_schedule_stall_timer(dev);

 	mutex_unlock(&dev->device_lock);
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Copyright (c) 2003-2018, Intel Corporation. All rights reserved.
	* Intel Management Engine Interface (Intel MEI) Linux driver
	*/

	#include <linux/export.h>
	#include <linux/kthread.h>
	#include <linux/interrupt.h>
	#include <linux/fs.h>
	#include <linux/jiffies.h>
	#include <linux/slab.h>
	#include <linux/pm_runtime.h>

	#include <linux/mei.h>

	#include "mei_dev.h"
	#include "hbm.h"
	#include "client.h"


	/**
	* mei_irq_compl_handler - dispatch complete handlers
	* for the completed callbacks
	*
	* @dev: mei device
	* @cmpl_list: list of completed cbs
	*/
	void mei_irq_compl_handler(struct mei_device dev, struct list_head cmpl_list)
	{
	struct mei_cl_cb cb, next;
	struct mei_cl *cl;

	list_for_each_entry_safe(cb, next, cmpl_list, list) {
	cl = cb->cl;
	list_del_init(&cb->list);

	dev_dbg(dev->dev, "completing call back.\n");
	mei_cl_complete(cl, cb);
	}
	}
	EXPORT_SYMBOL_GPL(mei_irq_compl_handler);

	/**
	* mei_cl_hbm_equal - check if hbm is addressed to the client
	*
	* @cl: host client
	* @mei_hdr: header of mei client message
	*
	* Return: true if matches, false otherwise
	*/
	static inline int mei_cl_hbm_equal(struct mei_cl *cl,
	struct mei_msg_hdr *mei_hdr)
	{
	return mei_cl_host_addr(cl) == mei_hdr->host_addr &&
	mei_cl_me_id(cl) == mei_hdr->me_addr;
	}

	/**
	* mei_irq_discard_msg - discard received message
	*
	* @dev: mei device
	* @hdr: message header
	* @discard_len: the length of the message to discard (excluding header)
	*/
	static void mei_irq_discard_msg(struct mei_device dev, struct mei_msg_hdr hdr,
	size_t discard_len)
	{
	if (hdr->dma_ring) {
	mei_dma_ring_read(dev, NULL,
	hdr->extension[dev->rd_msg_hdr_count - 2]);
	discard_len = 0;
	}
	/*
	* no need to check for size as it is guarantied
	* that length fits into rd_msg_buf
	*/
	mei_read_slots(dev, dev->rd_msg_buf, discard_len);
	dev_dbg(dev->dev, "discarding message " MEI_HDR_FMT "\n",
	MEI_HDR_PRM(hdr));
	}

	/**
	* mei_cl_irq_read_msg - process client message
	*
	* @cl: reading client
	* @mei_hdr: header of mei client message
	* @meta: extend meta header
	* @cmpl_list: completion list
	*
	* Return: always 0
	*/
	static int mei_cl_irq_read_msg(struct mei_cl *cl,
	struct mei_msg_hdr *mei_hdr,
	struct mei_ext_meta_hdr *meta,
	struct list_head *cmpl_list)
	{
	struct mei_device *dev = cl->dev;
	struct mei_cl_cb *cb;

	size_t buf_sz;
	u32 length;
	int ext_len;

	length = mei_hdr->length;
	ext_len = 0;
	if (mei_hdr->extended) {
	ext_len = sizeof(*meta) + mei_slots2data(meta->size);
	length -= ext_len;
	}

	cb = list_first_entry_or_null(&cl->rd_pending, struct mei_cl_cb, list);
	if (!cb) {
	if (!mei_cl_is_fixed_address(cl)) {
	cl_err(dev, cl, "pending read cb not found\n");
	goto discard;
	}
	cb = mei_cl_alloc_cb(cl, mei_cl_mtu(cl), MEI_FOP_READ, cl->fp);
	if (!cb)
	goto discard;
	list_add_tail(&cb->list, &cl->rd_pending);
	}

	if (mei_hdr->extended) {
	struct mei_ext_hdr *ext;
	struct mei_ext_hdr_vtag *vtag_hdr = NULL;

	ext = mei_ext_begin(meta);
	do {
	switch (ext->type) {
	case MEI_EXT_HDR_VTAG:
	vtag_hdr = (struct mei_ext_hdr_vtag *)ext;
	break;
	case MEI_EXT_HDR_NONE:
	fallthrough;
	default:
	cb->status = -EPROTO;
	break;
	}

	ext = mei_ext_next(ext);
	} while (!mei_ext_last(meta, ext));

	if (!vtag_hdr) {
	cl_dbg(dev, cl, "vtag not found in extended header.\n");
	cb->status = -EPROTO;
	goto discard;
	}

	cl_dbg(dev, cl, "vtag: %d\n", vtag_hdr->vtag);
	if (cb->vtag && cb->vtag != vtag_hdr->vtag) {
	cl_err(dev, cl, "mismatched tag: %d != %d\n",
	cb->vtag, vtag_hdr->vtag);
	cb->status = -EPROTO;
	goto discard;
	}
	cb->vtag = vtag_hdr->vtag;
	}

	if (!mei_cl_is_connected(cl)) {
	cl_dbg(dev, cl, "not connected\n");
	cb->status = -ENODEV;
	goto discard;
	}

	if (mei_hdr->dma_ring)
	length = mei_hdr->extension[mei_data2slots(ext_len)];

	buf_sz = length + cb->buf_idx;
	/* catch for integer overflow */
	if (buf_sz < cb->buf_idx) {
	cl_err(dev, cl, "message is too big len %d idx %zu\n",
	length, cb->buf_idx);
	cb->status = -EMSGSIZE;
	goto discard;
	}

	if (cb->buf.size < buf_sz) {
	cl_dbg(dev, cl, "message overflow. size %zu len %d idx %zu\n",
	cb->buf.size, length, cb->buf_idx);
	cb->status = -EMSGSIZE;
	goto discard;
	}

	if (mei_hdr->dma_ring) {
	mei_dma_ring_read(dev, cb->buf.data + cb->buf_idx, length);
	/* for DMA read 0 length to generate interrupt to the device */
	mei_read_slots(dev, cb->buf.data + cb->buf_idx, 0);
	} else {
	mei_read_slots(dev, cb->buf.data + cb->buf_idx, length);
	}

	cb->buf_idx += length;

	if (mei_hdr->msg_complete) {
	cl_dbg(dev, cl, "completed read length = %zu\n", cb->buf_idx);
	list_move_tail(&cb->list, cmpl_list);
	} else {
	pm_runtime_mark_last_busy(dev->dev);
	pm_request_autosuspend(dev->dev);
	}

	return 0;

	discard:
	if (cb)
	list_move_tail(&cb->list, cmpl_list);
	mei_irq_discard_msg(dev, mei_hdr, length);
	return 0;
	}

	/**
	* mei_cl_irq_disconnect_rsp - send disconnection response message
	*
	* @cl: client
	* @cb: callback block.
	* @cmpl_list: complete list.
	*
	* Return: 0, OK; otherwise, error.
	*/
	static int mei_cl_irq_disconnect_rsp(struct mei_cl cl, struct mei_cl_cb cb,
	struct list_head *cmpl_list)
	{
	struct mei_device *dev = cl->dev;
	u32 msg_slots;
	int slots;
	int ret;

	msg_slots = mei_hbm2slots(sizeof(struct hbm_client_connect_response));
	slots = mei_hbuf_empty_slots(dev);
	if (slots < 0)
	return -EOVERFLOW;

	if ((u32)slots < msg_slots)
	return -EMSGSIZE;

	ret = mei_hbm_cl_disconnect_rsp(dev, cl);
	list_move_tail(&cb->list, cmpl_list);

	return ret;
	}

	/**
	* mei_cl_irq_read - processes client read related operation from the
	* interrupt thread context - request for flow control credits
	*
	* @cl: client
	* @cb: callback block.
	* @cmpl_list: complete list.
	*
	* Return: 0, OK; otherwise, error.
	*/
	static int mei_cl_irq_read(struct mei_cl cl, struct mei_cl_cb cb,
	struct list_head *cmpl_list)
	{
	struct mei_device *dev = cl->dev;
	u32 msg_slots;
	int slots;
	int ret;

	if (!list_empty(&cl->rd_pending))
	return 0;

	msg_slots = mei_hbm2slots(sizeof(struct hbm_flow_control));
	slots = mei_hbuf_empty_slots(dev);
	if (slots < 0)
	return -EOVERFLOW;

	if ((u32)slots < msg_slots)
	return -EMSGSIZE;

	ret = mei_hbm_cl_flow_control_req(dev, cl);
	if (ret) {
	cl->status = ret;
	cb->buf_idx = 0;
	list_move_tail(&cb->list, cmpl_list);
	return ret;
	}

	pm_runtime_mark_last_busy(dev->dev);
	pm_request_autosuspend(dev->dev);

	list_move_tail(&cb->list, &cl->rd_pending);

	return 0;
	}

	static inline bool hdr_is_hbm(struct mei_msg_hdr *mei_hdr)
	{
	return mei_hdr->host_addr == 0 && mei_hdr->me_addr == 0;
	}

	static inline bool hdr_is_fixed(struct mei_msg_hdr *mei_hdr)
	{
	return mei_hdr->host_addr == 0 && mei_hdr->me_addr != 0;
	}

	static inline int hdr_is_valid(u32 msg_hdr)
	{
	struct mei_msg_hdr *mei_hdr;
	u32 expected_len = 0;

	mei_hdr = (struct mei_msg_hdr *)&msg_hdr;
	if (!msg_hdr \|\| mei_hdr->reserved)
	return -EBADMSG;

	if (mei_hdr->dma_ring)
	expected_len += MEI_SLOT_SIZE;
	if (mei_hdr->extended)
	expected_len += MEI_SLOT_SIZE;
	if (mei_hdr->length < expected_len)
	return -EBADMSG;

	return 0;
	}

	/**
	* mei_irq_read_handler - bottom half read routine after ISR to
	* handle the read processing.
	*
	* @dev: the device structure
	* @cmpl_list: An instance of our list structure
	* @slots: slots to read.
	*
	* Return: 0 on success, <0 on failure.
	*/
	int mei_irq_read_handler(struct mei_device *dev,
	struct list_head cmpl_list, s32 slots)
	{
	struct mei_msg_hdr *mei_hdr;
	struct mei_ext_meta_hdr *meta_hdr = NULL;
	struct mei_cl *cl;
	int ret;
	u32 hdr_size_left;
	u32 hdr_size_ext;
	int i;
	int ext_hdr_end;

	if (!dev->rd_msg_hdr[0]) {
	dev->rd_msg_hdr[0] = mei_read_hdr(dev);
	dev->rd_msg_hdr_count = 1;
	(*slots)--;
	dev_dbg(dev->dev, "slots =%08x.\n", *slots);

	ret = hdr_is_valid(dev->rd_msg_hdr[0]);
	if (ret) {
	dev_err(dev->dev, "corrupted message header 0x%08X\n",
	dev->rd_msg_hdr[0]);
	goto end;
	}
	}

	mei_hdr = (struct mei_msg_hdr *)dev->rd_msg_hdr;
	dev_dbg(dev->dev, MEI_HDR_FMT, MEI_HDR_PRM(mei_hdr));

	if (mei_slots2data(*slots) < mei_hdr->length) {
	dev_err(dev->dev, "less data available than length=%08x.\n",
	*slots);
	/* we can't read the message */
	ret = -ENODATA;
	goto end;
	}

	ext_hdr_end = 1;
	hdr_size_left = mei_hdr->length;

	if (mei_hdr->extended) {
	if (!dev->rd_msg_hdr[1]) {
	dev->rd_msg_hdr[1] = mei_read_hdr(dev);
	dev->rd_msg_hdr_count++;
	(*slots)--;
	dev_dbg(dev->dev, "extended header is %08x\n", dev->rd_msg_hdr[1]);
	}
	meta_hdr = ((struct mei_ext_meta_hdr *)&dev->rd_msg_hdr[1]);
	if (check_add_overflow((u32)sizeof(*meta_hdr),
	mei_slots2data(meta_hdr->size),
	&hdr_size_ext)) {
	dev_err(dev->dev, "extended message size too big %d\n",
	meta_hdr->size);
	return -EBADMSG;
	}
	if (hdr_size_left < hdr_size_ext) {
	dev_err(dev->dev, "corrupted message header len %d\n",
	mei_hdr->length);
	return -EBADMSG;
	}
	hdr_size_left -= hdr_size_ext;

	ext_hdr_end = meta_hdr->size + 2;
	for (i = dev->rd_msg_hdr_count; i < ext_hdr_end; i++) {
	dev->rd_msg_hdr[i] = mei_read_hdr(dev);
	dev_dbg(dev->dev, "extended header %d is %08x\n", i,
	dev->rd_msg_hdr[i]);
	dev->rd_msg_hdr_count++;
	(*slots)--;
	}
	}

	if (mei_hdr->dma_ring) {
	if (hdr_size_left != sizeof(dev->rd_msg_hdr[ext_hdr_end])) {
	dev_err(dev->dev, "corrupted message header len %d\n",
	mei_hdr->length);
	return -EBADMSG;
	}

	dev->rd_msg_hdr[ext_hdr_end] = mei_read_hdr(dev);
	dev->rd_msg_hdr_count++;
	(*slots)--;
	mei_hdr->length -= sizeof(dev->rd_msg_hdr[ext_hdr_end]);
	}

	/* HBM message */
	if (hdr_is_hbm(mei_hdr)) {
	ret = mei_hbm_dispatch(dev, mei_hdr);
	if (ret) {
	dev_dbg(dev->dev, "mei_hbm_dispatch failed ret = %d\n",
	ret);
	goto end;
	}
	goto reset_slots;
	}

	/* find recipient cl */
	list_for_each_entry(cl, &dev->file_list, link) {
	if (mei_cl_hbm_equal(cl, mei_hdr)) {
	cl_dbg(dev, cl, "got a message\n");
	ret = mei_cl_irq_read_msg(cl, mei_hdr, meta_hdr, cmpl_list);
	goto reset_slots;
	}
	}

	/* if no recipient cl was found we assume corrupted header */
	/* A message for not connected fixed address clients
	* should be silently discarded
	* On power down client may be force cleaned,
	* silently discard such messages
	*/
	if (hdr_is_fixed(mei_hdr) \|\|
	dev->dev_state == MEI_DEV_POWER_DOWN) {
	mei_irq_discard_msg(dev, mei_hdr, mei_hdr->length);
	ret = 0;
	goto reset_slots;
	}
	dev_err(dev->dev, "no destination client found 0x%08X\n", dev->rd_msg_hdr[0]);
	ret = -EBADMSG;
	goto end;

	reset_slots:
	/* reset the number of slots and header */
	memset(dev->rd_msg_hdr, 0, sizeof(dev->rd_msg_hdr));
	dev->rd_msg_hdr_count = 0;
	*slots = mei_count_full_read_slots(dev);
	if (*slots == -EOVERFLOW) {
	/* overflow - reset */
	dev_err(dev->dev, "resetting due to slots overflow.\n");
	/* set the event since message has been read */
	ret = -ERANGE;
	goto end;
	}
	end:
	return ret;
	}
	EXPORT_SYMBOL_GPL(mei_irq_read_handler);


	/**
	* mei_irq_write_handler - dispatch write requests
	* after irq received
	*
	* @dev: the device structure
	* @cmpl_list: An instance of our list structure
	*
	* Return: 0 on success, <0 on failure.
	*/
	int mei_irq_write_handler(struct mei_device dev, struct list_head cmpl_list)
	{

	struct mei_cl *cl;
	struct mei_cl_cb cb, next;
	s32 slots;
	int ret;


	if (!mei_hbuf_acquire(dev))
	return 0;

	slots = mei_hbuf_empty_slots(dev);
	if (slots < 0)
	return -EOVERFLOW;

	if (slots == 0)
	return -EMSGSIZE;

	/* complete all waiting for write CB */
	dev_dbg(dev->dev, "complete all waiting for write cb.\n");

	list_for_each_entry_safe(cb, next, &dev->write_waiting_list, list) {
	cl = cb->cl;

	cl->status = 0;
	cl_dbg(dev, cl, "MEI WRITE COMPLETE\n");
	cl->writing_state = MEI_WRITE_COMPLETE;
	list_move_tail(&cb->list, cmpl_list);
	}

	/* complete control write list CB */
	dev_dbg(dev->dev, "complete control write list cb.\n");
	list_for_each_entry_safe(cb, next, &dev->ctrl_wr_list, list) {
	cl = cb->cl;
	switch (cb->fop_type) {
	case MEI_FOP_DISCONNECT:
	/* send disconnect message */
	ret = mei_cl_irq_disconnect(cl, cb, cmpl_list);
	if (ret)
	return ret;

	break;
	case MEI_FOP_READ:
	/* send flow control message */
	ret = mei_cl_irq_read(cl, cb, cmpl_list);
	if (ret)
	return ret;

	break;
	case MEI_FOP_CONNECT:
	/* connect message */
	ret = mei_cl_irq_connect(cl, cb, cmpl_list);
	if (ret)
	return ret;

	break;
	case MEI_FOP_DISCONNECT_RSP:
	/* send disconnect resp */
	ret = mei_cl_irq_disconnect_rsp(cl, cb, cmpl_list);
	if (ret)
	return ret;
	break;

	case MEI_FOP_NOTIFY_START:
	case MEI_FOP_NOTIFY_STOP:
	ret = mei_cl_irq_notify(cl, cb, cmpl_list);
	if (ret)
	return ret;
	break;
	case MEI_FOP_DMA_MAP:
	ret = mei_cl_irq_dma_map(cl, cb, cmpl_list);
	if (ret)
	return ret;
	break;
	case MEI_FOP_DMA_UNMAP:
	ret = mei_cl_irq_dma_unmap(cl, cb, cmpl_list);
	if (ret)
	return ret;
	break;
	default:
	BUG();
	}

	}
	/* complete write list CB */
	dev_dbg(dev->dev, "complete write list cb.\n");
	list_for_each_entry_safe(cb, next, &dev->write_list, list) {
	cl = cb->cl;
	ret = mei_cl_irq_write(cl, cb, cmpl_list);
	if (ret)
	return ret;
	}
	return 0;
	}
	EXPORT_SYMBOL_GPL(mei_irq_write_handler);


	/**
	* mei_connect_timeout - connect/disconnect timeouts
	*
	* @cl: host client
	*/
	static void mei_connect_timeout(struct mei_cl *cl)
	{
	struct mei_device *dev = cl->dev;

	if (cl->state == MEI_FILE_CONNECTING) {
	if (dev->hbm_f_dot_supported) {
	cl->state = MEI_FILE_DISCONNECT_REQUIRED;
	wake_up(&cl->wait);
	return;
	}
	}
	mei_reset(dev);
	}

	#define MEI_STALL_TIMER_FREQ (2 * HZ)
	/**
	* mei_schedule_stall_timer - re-arm stall_timer work
	*
	* Schedule stall timer
	*
	* @dev: the device structure
	*/
	void mei_schedule_stall_timer(struct mei_device *dev)
	{
	schedule_delayed_work(&dev->timer_work, MEI_STALL_TIMER_FREQ);
	}

	/**
	* mei_timer - timer function.
	*
	* @work: pointer to the work_struct structure
	*
	*/
	void mei_timer(struct work_struct *work)
	{
	struct mei_cl *cl;
	struct mei_device *dev = container_of(work,
	struct mei_device, timer_work.work);
	bool reschedule_timer = false;

	mutex_lock(&dev->device_lock);

	/* Catch interrupt stalls during HBM init handshake */
	if (dev->dev_state == MEI_DEV_INIT_CLIENTS &&
	dev->hbm_state != MEI_HBM_IDLE) {

	if (dev->init_clients_timer) {
	if (--dev->init_clients_timer == 0) {
	dev_err(dev->dev, "timer: init clients timeout hbm_state = %d.\n",
	dev->hbm_state);
	mei_reset(dev);
	goto out;
	}
	reschedule_timer = true;
	}
	}

	if (dev->dev_state != MEI_DEV_ENABLED)
	goto out;

	/* connect/disconnect timeouts */
	list_for_each_entry(cl, &dev->file_list, link) {
	if (cl->timer_count) {
	if (--cl->timer_count == 0) {
	dev_err(dev->dev, "timer: connect/disconnect timeout.\n");
	mei_connect_timeout(cl);
	goto out;
	}
	reschedule_timer = true;
	}
	}

	out:
	if (dev->dev_state != MEI_DEV_DISABLED && reschedule_timer)
	mei_schedule_stall_timer(dev);

	mutex_unlock(&dev->device_lock);
	}