sound/firewire/fcp.c - third_party/kernel - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Function Control Protocol (IEC 61883-1) helper functions
  *
  * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
  */

 #include <linux/device.h>
 #include <linux/firewire.h>
 #include <linux/firewire-constants.h>
 #include <linux/list.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/sched.h>
 #include <linux/spinlock.h>
 #include <linux/wait.h>
 #include <linux/delay.h>
 #include "fcp.h"
 #include "lib.h"
 #include "amdtp-stream.h"

 #define CTS_AVC 0x00

 #define ERROR_RETRIES	3
 #define ERROR_DELAY_MS	5
 #define FCP_TIMEOUT_MS	125

 int avc_general_set_sig_fmt(struct fw_unit *unit, unsigned int rate,
 			    enum avc_general_plug_dir dir,
 			    unsigned short pid)
 {
 	unsigned int sfc;
 	u8 *buf;
 	bool flag;
 	int err;

 	flag = false;
 	for (sfc = 0; sfc < CIP_SFC_COUNT; sfc++) {
 		if (amdtp_rate_table[sfc] == rate) {
 			flag = true;
 			break;
 		}
 	}
 	if (!flag)
 		return -EINVAL;

 	buf = kzalloc(8, GFP_KERNEL);
 	if (buf == NULL)
 		return -ENOMEM;

 	buf[0] = 0x00;		/* AV/C CONTROL */
 	buf[1] = 0xff;		/* UNIT */
 	if (dir == AVC_GENERAL_PLUG_DIR_IN)
 		buf[2] = 0x19;	/* INPUT PLUG SIGNAL FORMAT */
 	else
 		buf[2] = 0x18;	/* OUTPUT PLUG SIGNAL FORMAT */
 	buf[3] = 0xff & pid;	/* plug id */
 	buf[4] = 0x90;		/* EOH_1, Form_1, FMT. AM824 */
 	buf[5] = 0x07 & sfc;	/* FDF-hi. AM824, frequency */
 	buf[6] = 0xff;		/* FDF-mid. AM824, SYT hi (not used)*/
 	buf[7] = 0xff;		/* FDF-low. AM824, SYT lo (not used) */

 	/* do transaction and check buf[1-5] are the same against command */
 	err = fcp_avc_transaction(unit, buf, 8, buf, 8,
 				  BIT(1) | BIT(2) | BIT(3) | BIT(4) | BIT(5));
 	if (err < 0)
 		;
 	else if (err < 8)
 		err = -EIO;
 	else if (buf[0] == 0x08) /* NOT IMPLEMENTED */
 		err = -ENOSYS;
 	else if (buf[0] == 0x0a) /* REJECTED */
 		err = -EINVAL;
 	if (err < 0)
 		goto end;

 	err = 0;
 end:
 	kfree(buf);
 	return err;
 }
 EXPORT_SYMBOL(avc_general_set_sig_fmt);

 int avc_general_get_sig_fmt(struct fw_unit *unit, unsigned int *rate,
 			    enum avc_general_plug_dir dir,
 			    unsigned short pid)
 {
 	unsigned int sfc;
 	u8 *buf;
 	int err;

 	buf = kzalloc(8, GFP_KERNEL);
 	if (buf == NULL)
 		return -ENOMEM;

 	buf[0] = 0x01;		/* AV/C STATUS */
 	buf[1] = 0xff;		/* Unit */
 	if (dir == AVC_GENERAL_PLUG_DIR_IN)
 		buf[2] = 0x19;	/* INPUT PLUG SIGNAL FORMAT */
 	else
 		buf[2] = 0x18;	/* OUTPUT PLUG SIGNAL FORMAT */
 	buf[3] = 0xff & pid;	/* plug id */
 	buf[4] = 0x90;		/* EOH_1, Form_1, FMT. AM824 */
 	buf[5] = 0xff;		/* FDF-hi. AM824, frequency */
 	buf[6] = 0xff;		/* FDF-mid. AM824, SYT hi (not used) */
 	buf[7] = 0xff;		/* FDF-low. AM824, SYT lo (not used) */

 	/* do transaction and check buf[1-4] are the same against command */
 	err = fcp_avc_transaction(unit, buf, 8, buf, 8,
 				  BIT(1) | BIT(2) | BIT(3) | BIT(4));
 	if (err < 0)
 		;
 	else if (err < 8)
 		err = -EIO;
 	else if (buf[0] == 0x08) /* NOT IMPLEMENTED */
 		err = -ENOSYS;
 	else if (buf[0] == 0x0a) /* REJECTED */
 		err = -EINVAL;
 	else if (buf[0] == 0x0b) /* IN TRANSITION */
 		err = -EAGAIN;
 	if (err < 0)
 		goto end;

 	/* check sfc field and pick up rate */
 	sfc = 0x07 & buf[5];
 	if (sfc >= CIP_SFC_COUNT) {
 		err = -EAGAIN;	/* also in transition */
 		goto end;
 	}

 	*rate = amdtp_rate_table[sfc];
 	err = 0;
 end:
 	kfree(buf);
 	return err;
 }
 EXPORT_SYMBOL(avc_general_get_sig_fmt);

 int avc_general_get_plug_info(struct fw_unit *unit, unsigned int subunit_type,
 			      unsigned int subunit_id, unsigned int subfunction,
 			      u8 info[AVC_PLUG_INFO_BUF_BYTES])
 {
 	u8 *buf;
 	int err;

 	/* extended subunit in spec.4.2 is not supported */
 	if ((subunit_type == 0x1E) || (subunit_id == 5))
 		return -EINVAL;

 	buf = kzalloc(8, GFP_KERNEL);
 	if (buf == NULL)
 		return -ENOMEM;

 	buf[0] = 0x01;	/* AV/C STATUS */
 	/* UNIT or Subunit, Functionblock */
 	buf[1] = ((subunit_type & 0x1f) << 3) | (subunit_id & 0x7);
 	buf[2] = 0x02;	/* PLUG INFO */
 	buf[3] = 0xff & subfunction;

 	err = fcp_avc_transaction(unit, buf, 8, buf, 8, BIT(1) | BIT(2));
 	if (err < 0)
 		;
 	else if (err < 8)
 		err = -EIO;
 	else if (buf[0] == 0x08) /* NOT IMPLEMENTED */
 		err = -ENOSYS;
 	else if (buf[0] == 0x0a) /* REJECTED */
 		err = -EINVAL;
 	else if (buf[0] == 0x0b) /* IN TRANSITION */
 		err = -EAGAIN;
 	if (err < 0)
 		goto end;

 	info[0] = buf[4];
 	info[1] = buf[5];
 	info[2] = buf[6];
 	info[3] = buf[7];

 	err = 0;
 end:
 	kfree(buf);
 	return err;
 }
 EXPORT_SYMBOL(avc_general_get_plug_info);

 static DEFINE_SPINLOCK(transactions_lock);
 static LIST_HEAD(transactions);

 enum fcp_state {
 	STATE_PENDING,
 	STATE_BUS_RESET,
 	STATE_COMPLETE,
 	STATE_DEFERRED,
 };

 struct fcp_transaction {
 	struct list_head list;
 	struct fw_unit *unit;
 	void *response_buffer;
 	unsigned int response_size;
 	unsigned int response_match_bytes;
 	enum fcp_state state;
 	wait_queue_head_t wait;
 	bool deferrable;
 };

 /**
  * fcp_avc_transaction - send an AV/C command and wait for its response
  * @unit: a unit on the target device
  * @command: a buffer containing the command frame; must be DMA-able
  * @command_size: the size of @command
  * @response: a buffer for the response frame
  * @response_size: the maximum size of @response
  * @response_match_bytes: a bitmap specifying the bytes used to detect the
  *                        correct response frame
  *
  * This function sends a FCP command frame to the target and waits for the
  * corresponding response frame to be returned.
  *
  * Because it is possible for multiple FCP transactions to be active at the
  * same time, the correct response frame is detected by the value of certain
  * bytes.  These bytes must be set in @response before calling this function,
  * and the corresponding bits must be set in @response_match_bytes.
  *
  * @command and @response can point to the same buffer.
  *
  * Returns the actual size of the response frame, or a negative error code.
  */
 int fcp_avc_transaction(struct fw_unit *unit,
 			const void *command, unsigned int command_size,
 			void *response, unsigned int response_size,
 			unsigned int response_match_bytes)
 {
 	struct fcp_transaction t;
 	int tcode, ret, tries = 0;

 	t.unit = unit;
 	t.response_buffer = response;
 	t.response_size = response_size;
 	t.response_match_bytes = response_match_bytes;
 	t.state = STATE_PENDING;
 	init_waitqueue_head(&t.wait);
 	t.deferrable = (*(const u8 *)command == 0x00 || *(const u8 *)command == 0x03);

 	spin_lock_irq(&transactions_lock);
 	list_add_tail(&t.list, &transactions);
 	spin_unlock_irq(&transactions_lock);

 	for (;;) {
 		tcode = command_size == 4 ? TCODE_WRITE_QUADLET_REQUEST
 					  : TCODE_WRITE_BLOCK_REQUEST;
 		ret = snd_fw_transaction(t.unit, tcode,
 					 CSR_REGISTER_BASE + CSR_FCP_COMMAND,
 					 (void *)command, command_size, 0);
 		if (ret < 0)
 			break;
 deferred:
 		wait_event_timeout(t.wait, t.state != STATE_PENDING,
 				   msecs_to_jiffies(FCP_TIMEOUT_MS));

 		if (t.state == STATE_DEFERRED) {
 			/*
 			 * 'AV/C General Specification' define no time limit
 			 * on command completion once an INTERIM response has
 			 * been sent. but we promise to finish this function
 			 * for a caller. Here we use FCP_TIMEOUT_MS for next
 			 * interval. This is not in the specification.
 			 */
 			t.state = STATE_PENDING;
 			goto deferred;
 		} else if (t.state == STATE_COMPLETE) {
 			ret = t.response_size;
 			break;
 		} else if (t.state == STATE_BUS_RESET) {
 			msleep(ERROR_DELAY_MS);
 		} else if (++tries >= ERROR_RETRIES) {
 			dev_err(&t.unit->device, "FCP command timed out\n");
 			ret = -EIO;
 			break;
 		}
 	}

 	spin_lock_irq(&transactions_lock);
 	list_del(&t.list);
 	spin_unlock_irq(&transactions_lock);

 	return ret;
 }
 EXPORT_SYMBOL(fcp_avc_transaction);

 /**
  * fcp_bus_reset - inform the target handler about a bus reset
  * @unit: the unit that might be used by fcp_avc_transaction()
  *
  * This function must be called from the driver's .update handler to inform
  * the FCP transaction handler that a bus reset has happened.  Any pending FCP
  * transactions are retried.
  */
 void fcp_bus_reset(struct fw_unit *unit)
 {
 	struct fcp_transaction *t;

 	spin_lock_irq(&transactions_lock);
 	list_for_each_entry(t, &transactions, list) {
 		if (t->unit == unit &&
 		    (t->state == STATE_PENDING ||
 		     t->state == STATE_DEFERRED)) {
 			t->state = STATE_BUS_RESET;
 			wake_up(&t->wait);
 		}
 	}
 	spin_unlock_irq(&transactions_lock);
 }
 EXPORT_SYMBOL(fcp_bus_reset);

 /* checks whether the response matches the masked bytes in response_buffer */
 static bool is_matching_response(struct fcp_transaction *transaction,
 				 const void *response, size_t length)
 {
 	const u8 *p1, *p2;
 	unsigned int mask, i;

 	p1 = response;
 	p2 = transaction->response_buffer;
 	mask = transaction->response_match_bytes;

 	for (i = 0; ; ++i) {
 		if ((mask & 1) && p1[i] != p2[i])
 			return false;
 		mask >>= 1;
 		if (!mask)
 			return true;
 		if (--length == 0)
 			return false;
 	}
 }

 static void fcp_response(struct fw_card *card, struct fw_request *request,
 			 int tcode, int destination, int source,
 			 int generation, unsigned long long offset,
 			 void *data, size_t length, void *callback_data)
 {
 	struct fcp_transaction *t;
 	unsigned long flags;

 	if (length < 1 || (*(const u8 *)data & 0xf0) != CTS_AVC)
 		return;

 	spin_lock_irqsave(&transactions_lock, flags);
 	list_for_each_entry(t, &transactions, list) {
 		struct fw_device *device = fw_parent_device(t->unit);
 		if (device->card != card ||
 		    device->generation != generation)
 			continue;
 		smp_rmb(); /* node_id vs. generation */
 		if (device->node_id != source)
 			continue;

 		if (t->state == STATE_PENDING &&
 		    is_matching_response(t, data, length)) {
 			if (t->deferrable && *(const u8 *)data == 0x0f) {
 				t->state = STATE_DEFERRED;
 			} else {
 				t->state = STATE_COMPLETE;
 				t->response_size = min_t(unsigned int, length,
 							 t->response_size);
 				memcpy(t->response_buffer, data,
 				       t->response_size);
 			}
 			wake_up(&t->wait);
 		}
 	}
 	spin_unlock_irqrestore(&transactions_lock, flags);
 }

 static struct fw_address_handler response_register_handler = {
 	.length = 0x200,
 	.address_callback = fcp_response,
 };

 static int __init fcp_module_init(void)
 {
 	static const struct fw_address_region response_register_region = {
 		.start = CSR_REGISTER_BASE + CSR_FCP_RESPONSE,
 		.end = CSR_REGISTER_BASE + CSR_FCP_END,
 	};

 	fw_core_add_address_handler(&response_register_handler,
 				    &response_register_region);

 	return 0;
 }

 static void __exit fcp_module_exit(void)
 {
 	WARN_ON(!list_empty(&transactions));
 	fw_core_remove_address_handler(&response_register_handler);
 }

 module_init(fcp_module_init);
 module_exit(fcp_module_exit);
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Function Control Protocol (IEC 61883-1) helper functions
	*
	* Copyright (c) Clemens Ladisch <clemens@ladisch.de>
	*/

	#include <linux/device.h>
	#include <linux/firewire.h>
	#include <linux/firewire-constants.h>
	#include <linux/list.h>
	#include <linux/module.h>
	#include <linux/slab.h>
	#include <linux/sched.h>
	#include <linux/spinlock.h>
	#include <linux/wait.h>
	#include <linux/delay.h>
	#include "fcp.h"
	#include "lib.h"
	#include "amdtp-stream.h"

	#define CTS_AVC 0x00

	#define ERROR_RETRIES 3
	#define ERROR_DELAY_MS 5
	#define FCP_TIMEOUT_MS 125

	int avc_general_set_sig_fmt(struct fw_unit *unit, unsigned int rate,
	enum avc_general_plug_dir dir,
	unsigned short pid)
	{
	unsigned int sfc;
	u8 *buf;
	bool flag;
	int err;

	flag = false;
	for (sfc = 0; sfc < CIP_SFC_COUNT; sfc++) {
	if (amdtp_rate_table[sfc] == rate) {
	flag = true;
	break;
	}
	}
	if (!flag)
	return -EINVAL;

	buf = kzalloc(8, GFP_KERNEL);
	if (buf == NULL)
	return -ENOMEM;

	buf[0] = 0x00; /* AV/C CONTROL */
	buf[1] = 0xff; /* UNIT */
	if (dir == AVC_GENERAL_PLUG_DIR_IN)
	buf[2] = 0x19; /* INPUT PLUG SIGNAL FORMAT */
	else
	buf[2] = 0x18; /* OUTPUT PLUG SIGNAL FORMAT */
	buf[3] = 0xff & pid; /* plug id */
	buf[4] = 0x90; /* EOH_1, Form_1, FMT. AM824 */
	buf[5] = 0x07 & sfc; /* FDF-hi. AM824, frequency */
	buf[6] = 0xff; /* FDF-mid. AM824, SYT hi (not used)*/
	buf[7] = 0xff; /* FDF-low. AM824, SYT lo (not used) */

	/* do transaction and check buf[1-5] are the same against command */
	err = fcp_avc_transaction(unit, buf, 8, buf, 8,
	BIT(1) \| BIT(2) \| BIT(3) \| BIT(4) \| BIT(5));
	if (err < 0)
	;
	else if (err < 8)
	err = -EIO;
	else if (buf[0] == 0x08) /* NOT IMPLEMENTED */
	err = -ENOSYS;
	else if (buf[0] == 0x0a) /* REJECTED */
	err = -EINVAL;
	if (err < 0)
	goto end;

	err = 0;
	end:
	kfree(buf);
	return err;
	}
	EXPORT_SYMBOL(avc_general_set_sig_fmt);

	int avc_general_get_sig_fmt(struct fw_unit unit, unsigned int rate,
	enum avc_general_plug_dir dir,
	unsigned short pid)
	{
	unsigned int sfc;
	u8 *buf;
	int err;

	buf = kzalloc(8, GFP_KERNEL);
	if (buf == NULL)
	return -ENOMEM;

	buf[0] = 0x01; /* AV/C STATUS */
	buf[1] = 0xff; /* Unit */
	if (dir == AVC_GENERAL_PLUG_DIR_IN)
	buf[2] = 0x19; /* INPUT PLUG SIGNAL FORMAT */
	else
	buf[2] = 0x18; /* OUTPUT PLUG SIGNAL FORMAT */
	buf[3] = 0xff & pid; /* plug id */
	buf[4] = 0x90; /* EOH_1, Form_1, FMT. AM824 */
	buf[5] = 0xff; /* FDF-hi. AM824, frequency */
	buf[6] = 0xff; /* FDF-mid. AM824, SYT hi (not used) */
	buf[7] = 0xff; /* FDF-low. AM824, SYT lo (not used) */

	/* do transaction and check buf[1-4] are the same against command */
	err = fcp_avc_transaction(unit, buf, 8, buf, 8,
	BIT(1) \| BIT(2) \| BIT(3) \| BIT(4));
	if (err < 0)
	;
	else if (err < 8)
	err = -EIO;
	else if (buf[0] == 0x08) /* NOT IMPLEMENTED */
	err = -ENOSYS;
	else if (buf[0] == 0x0a) /* REJECTED */
	err = -EINVAL;
	else if (buf[0] == 0x0b) /* IN TRANSITION */
	err = -EAGAIN;
	if (err < 0)
	goto end;

	/* check sfc field and pick up rate */
	sfc = 0x07 & buf[5];
	if (sfc >= CIP_SFC_COUNT) {
	err = -EAGAIN; /* also in transition */
	goto end;
	}

	*rate = amdtp_rate_table[sfc];
	err = 0;
	end:
	kfree(buf);
	return err;
	}
	EXPORT_SYMBOL(avc_general_get_sig_fmt);

	int avc_general_get_plug_info(struct fw_unit *unit, unsigned int subunit_type,
	unsigned int subunit_id, unsigned int subfunction,
	u8 info[AVC_PLUG_INFO_BUF_BYTES])
	{
	u8 *buf;
	int err;

	/* extended subunit in spec.4.2 is not supported */
	if ((subunit_type == 0x1E) \|\| (subunit_id == 5))
	return -EINVAL;

	buf = kzalloc(8, GFP_KERNEL);
	if (buf == NULL)
	return -ENOMEM;

	buf[0] = 0x01; /* AV/C STATUS */
	/* UNIT or Subunit, Functionblock */
	buf[1] = ((subunit_type & 0x1f) << 3) \| (subunit_id & 0x7);
	buf[2] = 0x02; /* PLUG INFO */
	buf[3] = 0xff & subfunction;

	err = fcp_avc_transaction(unit, buf, 8, buf, 8, BIT(1) \| BIT(2));
	if (err < 0)
	;
	else if (err < 8)
	err = -EIO;
	else if (buf[0] == 0x08) /* NOT IMPLEMENTED */
	err = -ENOSYS;
	else if (buf[0] == 0x0a) /* REJECTED */
	err = -EINVAL;
	else if (buf[0] == 0x0b) /* IN TRANSITION */
	err = -EAGAIN;
	if (err < 0)
	goto end;

	info[0] = buf[4];
	info[1] = buf[5];
	info[2] = buf[6];
	info[3] = buf[7];

	err = 0;
	end:
	kfree(buf);
	return err;
	}
	EXPORT_SYMBOL(avc_general_get_plug_info);

	static DEFINE_SPINLOCK(transactions_lock);
	static LIST_HEAD(transactions);

	enum fcp_state {
	STATE_PENDING,
	STATE_BUS_RESET,
	STATE_COMPLETE,
	STATE_DEFERRED,
	};

	struct fcp_transaction {
	struct list_head list;
	struct fw_unit *unit;
	void *response_buffer;
	unsigned int response_size;
	unsigned int response_match_bytes;
	enum fcp_state state;
	wait_queue_head_t wait;
	bool deferrable;
	};

	/**
	* fcp_avc_transaction - send an AV/C command and wait for its response
	* @unit: a unit on the target device
	* @command: a buffer containing the command frame; must be DMA-able
	* @command_size: the size of @command
	* @response: a buffer for the response frame
	* @response_size: the maximum size of @response
	* @response_match_bytes: a bitmap specifying the bytes used to detect the
	* correct response frame
	*
	* This function sends a FCP command frame to the target and waits for the
	* corresponding response frame to be returned.
	*
	* Because it is possible for multiple FCP transactions to be active at the
	* same time, the correct response frame is detected by the value of certain
	* bytes. These bytes must be set in @response before calling this function,
	* and the corresponding bits must be set in @response_match_bytes.
	*
	* @command and @response can point to the same buffer.
	*
	* Returns the actual size of the response frame, or a negative error code.
	*/
	int fcp_avc_transaction(struct fw_unit *unit,
	const void *command, unsigned int command_size,
	void *response, unsigned int response_size,
	unsigned int response_match_bytes)
	{
	struct fcp_transaction t;
	int tcode, ret, tries = 0;

	t.unit = unit;
	t.response_buffer = response;
	t.response_size = response_size;
	t.response_match_bytes = response_match_bytes;
	t.state = STATE_PENDING;
	init_waitqueue_head(&t.wait);
	t.deferrable = ((const u8 )command == 0x00 \|\| (const u8 )command == 0x03);

	spin_lock_irq(&transactions_lock);
	list_add_tail(&t.list, &transactions);
	spin_unlock_irq(&transactions_lock);

	for (;;) {
	tcode = command_size == 4 ? TCODE_WRITE_QUADLET_REQUEST
	: TCODE_WRITE_BLOCK_REQUEST;
	ret = snd_fw_transaction(t.unit, tcode,
	CSR_REGISTER_BASE + CSR_FCP_COMMAND,
	(void *)command, command_size, 0);
	if (ret < 0)
	break;
	deferred:
	wait_event_timeout(t.wait, t.state != STATE_PENDING,
	msecs_to_jiffies(FCP_TIMEOUT_MS));

	if (t.state == STATE_DEFERRED) {
	/*
	* 'AV/C General Specification' define no time limit
	* on command completion once an INTERIM response has
	* been sent. but we promise to finish this function
	* for a caller. Here we use FCP_TIMEOUT_MS for next
	* interval. This is not in the specification.
	*/
	t.state = STATE_PENDING;
	goto deferred;
	} else if (t.state == STATE_COMPLETE) {
	ret = t.response_size;
	break;
	} else if (t.state == STATE_BUS_RESET) {
	msleep(ERROR_DELAY_MS);
	} else if (++tries >= ERROR_RETRIES) {
	dev_err(&t.unit->device, "FCP command timed out\n");
	ret = -EIO;
	break;
	}
	}

	spin_lock_irq(&transactions_lock);
	list_del(&t.list);
	spin_unlock_irq(&transactions_lock);

	return ret;
	}
	EXPORT_SYMBOL(fcp_avc_transaction);

	/**
	* fcp_bus_reset - inform the target handler about a bus reset
	* @unit: the unit that might be used by fcp_avc_transaction()
	*
	* This function must be called from the driver's .update handler to inform
	* the FCP transaction handler that a bus reset has happened. Any pending FCP
	* transactions are retried.
	*/
	void fcp_bus_reset(struct fw_unit *unit)
	{
	struct fcp_transaction *t;

	spin_lock_irq(&transactions_lock);
	list_for_each_entry(t, &transactions, list) {
	if (t->unit == unit &&
	(t->state == STATE_PENDING \|\|
	t->state == STATE_DEFERRED)) {
	t->state = STATE_BUS_RESET;
	wake_up(&t->wait);
	}
	}
	spin_unlock_irq(&transactions_lock);
	}
	EXPORT_SYMBOL(fcp_bus_reset);

	/* checks whether the response matches the masked bytes in response_buffer */
	static bool is_matching_response(struct fcp_transaction *transaction,
	const void *response, size_t length)
	{
	const u8 p1, p2;
	unsigned int mask, i;

	p1 = response;
	p2 = transaction->response_buffer;
	mask = transaction->response_match_bytes;

	for (i = 0; ; ++i) {
	if ((mask & 1) && p1[i] != p2[i])
	return false;
	mask >>= 1;
	if (!mask)
	return true;
	if (--length == 0)
	return false;
	}
	}

	static void fcp_response(struct fw_card card, struct fw_request request,
	int tcode, int destination, int source,
	int generation, unsigned long long offset,
	void data, size_t length, void callback_data)
	{
	struct fcp_transaction *t;
	unsigned long flags;

	if (length < 1 \|\| ((const u8 )data & 0xf0) != CTS_AVC)
	return;

	spin_lock_irqsave(&transactions_lock, flags);
	list_for_each_entry(t, &transactions, list) {
	struct fw_device *device = fw_parent_device(t->unit);
	if (device->card != card \|\|
	device->generation != generation)
	continue;
	smp_rmb(); /* node_id vs. generation */
	if (device->node_id != source)
	continue;

	if (t->state == STATE_PENDING &&
	is_matching_response(t, data, length)) {
	if (t->deferrable && (const u8 )data == 0x0f) {
	t->state = STATE_DEFERRED;
	} else {
	t->state = STATE_COMPLETE;
	t->response_size = min_t(unsigned int, length,
	t->response_size);
	memcpy(t->response_buffer, data,
	t->response_size);
	}
	wake_up(&t->wait);
	}
	}
	spin_unlock_irqrestore(&transactions_lock, flags);
	}

	static struct fw_address_handler response_register_handler = {
	.length = 0x200,
	.address_callback = fcp_response,
	};

	static int __init fcp_module_init(void)
	{
	static const struct fw_address_region response_register_region = {
	.start = CSR_REGISTER_BASE + CSR_FCP_RESPONSE,
	.end = CSR_REGISTER_BASE + CSR_FCP_END,
	};

	fw_core_add_address_handler(&response_register_handler,
	&response_register_region);

	return 0;
	}

	static void __exit fcp_module_exit(void)
	{
	WARN_ON(!list_empty(&transactions));
	fw_core_remove_address_handler(&response_register_handler);
	}

	module_init(fcp_module_init);
	module_exit(fcp_module_exit);