ide-tape.c 112 KB
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/*
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 * IDE ATAPI streaming tape driver.
 *
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 * Copyright (C) 1995-1999  Gadi Oxman <gadio@netvision.net.il>
 * Copyright (C) 2003-2005  Bartlomiej Zolnierkiewicz
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 *
 * This driver was constructed as a student project in the software laboratory
 * of the faculty of electrical engineering in the Technion - Israel's
 * Institute Of Technology, with the guide of Avner Lottem and Dr. Ilana David.
 *
 * It is hereby placed under the terms of the GNU general public license.
 * (See linux/COPYING).
 *
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 * For a historical changelog see
 * Documentation/ide/ChangeLog.ide-tape.1995-2002
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 */

#define IDETAPE_VERSION "1.19"

#include <linux/module.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/timer.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
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#include <linux/jiffies.h>
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#include <linux/major.h>
#include <linux/errno.h>
#include <linux/genhd.h>
#include <linux/slab.h>
#include <linux/pci.h>
#include <linux/ide.h>
#include <linux/smp_lock.h>
#include <linux/completion.h>
#include <linux/bitops.h>
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#include <linux/mutex.h>
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#include <scsi/scsi.h>
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#include <asm/byteorder.h>
#include <asm/irq.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/unaligned.h>
#include <linux/mtio.h>

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enum {
	/* output errors only */
	DBG_ERR =		(1 << 0),
	/* output all sense key/asc */
	DBG_SENSE =		(1 << 1),
	/* info regarding all chrdev-related procedures */
	DBG_CHRDEV =		(1 << 2),
	/* all remaining procedures */
	DBG_PROCS =		(1 << 3),
	/* buffer alloc info (pc_stack & rq_stack) */
	DBG_PCRQ_STACK =	(1 << 4),
};

/* define to see debug info */
#define IDETAPE_DEBUG_LOG		0

#if IDETAPE_DEBUG_LOG
#define debug_log(lvl, fmt, args...)			\
{							\
	if (tape->debug_mask & lvl)			\
	printk(KERN_INFO "ide-tape: " fmt, ## args);	\
}
#else
#define debug_log(lvl, fmt, args...) do {} while (0)
#endif

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/**************************** Tunable parameters *****************************/


/*
 *	Pipelined mode parameters.
 *
 *	We try to use the minimum number of stages which is enough to
 *	keep the tape constantly streaming. To accomplish that, we implement
 *	a feedback loop around the maximum number of stages:
 *
 *	We start from MIN maximum stages (we will not even use MIN stages
 *      if we don't need them), increment it by RATE*(MAX-MIN)
 *	whenever we sense that the pipeline is empty, until we reach
 *	the optimum value or until we reach MAX.
 *
 *	Setting the following parameter to 0 is illegal: the pipelined mode
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 *	cannot be disabled (idetape_calculate_speeds() divides by
 *	tape->max_stages.)
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 */
#define IDETAPE_MIN_PIPELINE_STAGES	  1
#define IDETAPE_MAX_PIPELINE_STAGES	400
#define IDETAPE_INCREASE_STAGES_RATE	 20

/*
 *	After each failed packet command we issue a request sense command
 *	and retry the packet command IDETAPE_MAX_PC_RETRIES times.
 *
 *	Setting IDETAPE_MAX_PC_RETRIES to 0 will disable retries.
 */
#define IDETAPE_MAX_PC_RETRIES		3

/*
 *	With each packet command, we allocate a buffer of
 *	IDETAPE_PC_BUFFER_SIZE bytes. This is used for several packet
 *	commands (Not for READ/WRITE commands).
 */
#define IDETAPE_PC_BUFFER_SIZE		256

/*
 *	In various places in the driver, we need to allocate storage
 *	for packet commands and requests, which will remain valid while
 *	we leave the driver to wait for an interrupt or a timeout event.
 */
#define IDETAPE_PC_STACK		(10 + IDETAPE_MAX_PC_RETRIES)

/*
 * Some drives (for example, Seagate STT3401A Travan) require a very long
 * timeout, because they don't return an interrupt or clear their busy bit
 * until after the command completes (even retension commands).
 */
#define IDETAPE_WAIT_CMD		(900*HZ)

/*
 *	The following parameter is used to select the point in the internal
 *	tape fifo in which we will start to refill the buffer. Decreasing
 *	the following parameter will improve the system's latency and
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 *	interactive response, while using a high value might improve system
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 *	throughput.
 */
#define IDETAPE_FIFO_THRESHOLD 		2

/*
 *	DSC polling parameters.
 *
 *	Polling for DSC (a single bit in the status register) is a very
 *	important function in ide-tape. There are two cases in which we
 *	poll for DSC:
 *
 *	1.	Before a read/write packet command, to ensure that we
 *		can transfer data from/to the tape's data buffers, without
 *		causing an actual media access. In case the tape is not
 *		ready yet, we take out our request from the device
 *		request queue, so that ide.c will service requests from
 *		the other device on the same interface meanwhile.
 *
 *	2.	After the successful initialization of a "media access
 *		packet command", which is a command which can take a long
 *		time to complete (it can be several seconds or even an hour).
 *
 *		Again, we postpone our request in the middle to free the bus
 *		for the other device. The polling frequency here should be
 *		lower than the read/write frequency since those media access
 *		commands are slow. We start from a "fast" frequency -
 *		IDETAPE_DSC_MA_FAST (one second), and if we don't receive DSC
 *		after IDETAPE_DSC_MA_THRESHOLD (5 minutes), we switch it to a
 *		lower frequency - IDETAPE_DSC_MA_SLOW (1 minute).
 *
 *	We also set a timeout for the timer, in case something goes wrong.
 *	The timeout should be longer then the maximum execution time of a
 *	tape operation.
 */
 
/*
 *	DSC timings.
 */
#define IDETAPE_DSC_RW_MIN		5*HZ/100	/* 50 msec */
#define IDETAPE_DSC_RW_MAX		40*HZ/100	/* 400 msec */
#define IDETAPE_DSC_RW_TIMEOUT		2*60*HZ		/* 2 minutes */
#define IDETAPE_DSC_MA_FAST		2*HZ		/* 2 seconds */
#define IDETAPE_DSC_MA_THRESHOLD	5*60*HZ		/* 5 minutes */
#define IDETAPE_DSC_MA_SLOW		30*HZ		/* 30 seconds */
#define IDETAPE_DSC_MA_TIMEOUT		2*60*60*HZ	/* 2 hours */

/*************************** End of tunable parameters ***********************/

/*
 *	Read/Write error simulation
 */
#define SIMULATE_ERRORS			0

/*
 *	For general magnetic tape device compatibility.
 */
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/* tape directions */
enum {
	IDETAPE_DIR_NONE  = (1 << 0),
	IDETAPE_DIR_READ  = (1 << 1),
	IDETAPE_DIR_WRITE = (1 << 2),
};
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struct idetape_bh {
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	u32 b_size;
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	atomic_t b_count;
	struct idetape_bh *b_reqnext;
	char *b_data;
};

/*
 *	Our view of a packet command.
 */
typedef struct idetape_packet_command_s {
	u8 c[12];				/* Actual packet bytes */
	int retries;				/* On each retry, we increment retries */
	int error;				/* Error code */
	int request_transfer;			/* Bytes to transfer */
	int actually_transferred;		/* Bytes actually transferred */
	int buffer_size;			/* Size of our data buffer */
	struct idetape_bh *bh;
	char *b_data;
	int b_count;
	u8 *buffer;				/* Data buffer */
	u8 *current_position;			/* Pointer into the above buffer */
	ide_startstop_t (*callback) (ide_drive_t *);	/* Called when this packet command is completed */
	u8 pc_buffer[IDETAPE_PC_BUFFER_SIZE];	/* Temporary buffer */
	unsigned long flags;			/* Status/Action bit flags: long for set_bit */
} idetape_pc_t;

/*
 *	Packet command flag bits.
 */
/* Set when an error is considered normal - We won't retry */
#define	PC_ABORT			0
/* 1 When polling for DSC on a media access command */
#define PC_WAIT_FOR_DSC			1
/* 1 when we prefer to use DMA if possible */
#define PC_DMA_RECOMMENDED		2
/* 1 while DMA in progress */
#define	PC_DMA_IN_PROGRESS		3
/* 1 when encountered problem during DMA */
#define	PC_DMA_ERROR			4
/* Data direction */
#define	PC_WRITING			5

/*
 *	A pipeline stage.
 */
typedef struct idetape_stage_s {
	struct request rq;			/* The corresponding request */
	struct idetape_bh *bh;			/* The data buffers */
	struct idetape_stage_s *next;		/* Pointer to the next stage */
} idetape_stage_t;

/*
 *	Most of our global data which we need to save even as we leave the
 *	driver due to an interrupt or a timer event is stored in a variable
 *	of type idetape_tape_t, defined below.
 */
typedef struct ide_tape_obj {
	ide_drive_t	*drive;
	ide_driver_t	*driver;
	struct gendisk	*disk;
	struct kref	kref;

	/*
	 *	Since a typical character device operation requires more
	 *	than one packet command, we provide here enough memory
	 *	for the maximum of interconnected packet commands.
	 *	The packet commands are stored in the circular array pc_stack.
	 *	pc_stack_index points to the last used entry, and warps around
	 *	to the start when we get to the last array entry.
	 *
	 *	pc points to the current processed packet command.
	 *
	 *	failed_pc points to the last failed packet command, or contains
	 *	NULL if we do not need to retry any packet command. This is
	 *	required since an additional packet command is needed before the
	 *	retry, to get detailed information on what went wrong.
	 */
	/* Current packet command */
	idetape_pc_t *pc;
	/* Last failed packet command */
	idetape_pc_t *failed_pc;
	/* Packet command stack */
	idetape_pc_t pc_stack[IDETAPE_PC_STACK];
	/* Next free packet command storage space */
	int pc_stack_index;
	struct request rq_stack[IDETAPE_PC_STACK];
	/* We implement a circular array */
	int rq_stack_index;

	/*
	 *	DSC polling variables.
	 *
	 *	While polling for DSC we use postponed_rq to postpone the
	 *	current request so that ide.c will be able to service
	 *	pending requests on the other device. Note that at most
	 *	we will have only one DSC (usually data transfer) request
	 *	in the device request queue. Additional requests can be
	 *	queued in our internal pipeline, but they will be visible
	 *	to ide.c only one at a time.
	 */
	struct request *postponed_rq;
	/* The time in which we started polling for DSC */
	unsigned long dsc_polling_start;
	/* Timer used to poll for dsc */
	struct timer_list dsc_timer;
	/* Read/Write dsc polling frequency */
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	unsigned long best_dsc_rw_freq;
	unsigned long dsc_poll_freq;
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	unsigned long dsc_timeout;

	/*
	 *	Read position information
	 */
	u8 partition;
	/* Current block */
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	unsigned int first_frame;
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	/*
	 *	Last error information
	 */
	u8 sense_key, asc, ascq;

	/*
	 *	Character device operation
	 */
	unsigned int minor;
	/* device name */
	char name[4];
	/* Current character device data transfer direction */
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	u8 chrdev_dir;
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	/* tape block size, usually 512 or 1024 bytes */
	unsigned short blk_size;
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	int user_bs_factor;
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	/* Copy of the tape's Capabilities and Mechanical Page */
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	u8 caps[20];
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	/*
	 *	Active data transfer request parameters.
	 *
	 *	At most, there is only one ide-tape originated data transfer
	 *	request in the device request queue. This allows ide.c to
	 *	easily service requests from the other device when we
	 *	postpone our active request. In the pipelined operation
	 *	mode, we use our internal pipeline structure to hold
	 *	more data requests.
	 *
	 *	The data buffer size is chosen based on the tape's
	 *	recommendation.
	 */
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	/* Ptr to the request which is waiting in the device request queue */
	struct request *active_data_rq;
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	/* Data buffer size (chosen based on the tape's recommendation */
	int stage_size;
	idetape_stage_t *merge_stage;
	int merge_stage_size;
	struct idetape_bh *bh;
	char *b_data;
	int b_count;
	
	/*
	 *	Pipeline parameters.
	 *
	 *	To accomplish non-pipelined mode, we simply set the following
	 *	variables to zero (or NULL, where appropriate).
	 */
	/* Number of currently used stages */
	int nr_stages;
	/* Number of pending stages */
	int nr_pending_stages;
	/* We will not allocate more than this number of stages */
	int max_stages, min_pipeline, max_pipeline;
	/* The first stage which will be removed from the pipeline */
	idetape_stage_t *first_stage;
	/* The currently active stage */
	idetape_stage_t *active_stage;
	/* Will be serviced after the currently active request */
	idetape_stage_t *next_stage;
	/* New requests will be added to the pipeline here */
	idetape_stage_t *last_stage;
	/* Optional free stage which we can use */
	idetape_stage_t *cache_stage;
	int pages_per_stage;
	/* Wasted space in each stage */
	int excess_bh_size;

	/* Status/Action flags: long for set_bit */
	unsigned long flags;
	/* protects the ide-tape queue */
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	spinlock_t lock;
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	/*
	 * Measures average tape speed
	 */
	unsigned long avg_time;
	int avg_size;
	int avg_speed;

	/* the door is currently locked */
	int door_locked;
	/* the tape hardware is write protected */
	char drv_write_prot;
	/* the tape is write protected (hardware or opened as read-only) */
	char write_prot;

	/*
	 * Limit the number of times a request can
	 * be postponed, to avoid an infinite postpone
	 * deadlock.
	 */
	/* request postpone count limit */
	int postpone_cnt;

	/*
	 * Measures number of frames:
	 *
	 * 1. written/read to/from the driver pipeline (pipeline_head).
	 * 2. written/read to/from the tape buffers (idetape_bh).
	 * 3. written/read by the tape to/from the media (tape_head).
	 */
	int pipeline_head;
	int buffer_head;
	int tape_head;
	int last_tape_head;

	/*
	 * Speed control at the tape buffers input/output
	 */
	unsigned long insert_time;
	int insert_size;
	int insert_speed;
	int max_insert_speed;
	int measure_insert_time;

	/*
	 * Speed regulation negative feedback loop
	 */
	int speed_control;
	int pipeline_head_speed;
	int controlled_pipeline_head_speed;
	int uncontrolled_pipeline_head_speed;
	int controlled_last_pipeline_head;
	unsigned long uncontrolled_pipeline_head_time;
	unsigned long controlled_pipeline_head_time;
	int controlled_previous_pipeline_head;
	int uncontrolled_previous_pipeline_head;
	unsigned long controlled_previous_head_time;
	unsigned long uncontrolled_previous_head_time;
	int restart_speed_control_req;

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	u32 debug_mask;
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} idetape_tape_t;

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static DEFINE_MUTEX(idetape_ref_mutex);
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static struct class *idetape_sysfs_class;

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#define to_ide_tape(obj) container_of(obj, struct ide_tape_obj, kref)

#define ide_tape_g(disk) \
	container_of((disk)->private_data, struct ide_tape_obj, driver)

static struct ide_tape_obj *ide_tape_get(struct gendisk *disk)
{
	struct ide_tape_obj *tape = NULL;

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	mutex_lock(&idetape_ref_mutex);
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	tape = ide_tape_g(disk);
	if (tape)
		kref_get(&tape->kref);
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	mutex_unlock(&idetape_ref_mutex);
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	return tape;
}

static void ide_tape_release(struct kref *);

static void ide_tape_put(struct ide_tape_obj *tape)
{
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	mutex_lock(&idetape_ref_mutex);
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	kref_put(&tape->kref, ide_tape_release);
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	mutex_unlock(&idetape_ref_mutex);
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}

/*
 *	Tape door status
 */
#define DOOR_UNLOCKED			0
#define DOOR_LOCKED			1
#define DOOR_EXPLICITLY_LOCKED		2

/*
 *	Tape flag bits values.
 */
#define IDETAPE_IGNORE_DSC		0
#define IDETAPE_ADDRESS_VALID		1	/* 0 When the tape position is unknown */
#define IDETAPE_BUSY			2	/* Device already opened */
#define IDETAPE_PIPELINE_ERROR		3	/* Error detected in a pipeline stage */
#define IDETAPE_DETECT_BS		4	/* Attempt to auto-detect the current user block size */
#define IDETAPE_FILEMARK		5	/* Currently on a filemark */
#define IDETAPE_DRQ_INTERRUPT		6	/* DRQ interrupt device */
#define IDETAPE_READ_ERROR		7
#define IDETAPE_PIPELINE_ACTIVE		8	/* pipeline active */
/* 0 = no tape is loaded, so we don't rewind after ejecting */
#define IDETAPE_MEDIUM_PRESENT		9

/*
 *	Some defines for the READ BUFFER command
 */
#define IDETAPE_RETRIEVE_FAULTY_BLOCK	6

/*
 *	Some defines for the SPACE command
 */
#define IDETAPE_SPACE_OVER_FILEMARK	1
#define IDETAPE_SPACE_TO_EOD		3

/*
 *	Some defines for the LOAD UNLOAD command
 */
#define IDETAPE_LU_LOAD_MASK		1
#define IDETAPE_LU_RETENSION_MASK	2
#define IDETAPE_LU_EOT_MASK		4

/*
 *	Special requests for our block device strategy routine.
 *
 *	In order to service a character device command, we add special
 *	requests to the tail of our block device request queue and wait
 *	for their completion.
 */

enum {
	REQ_IDETAPE_PC1		= (1 << 0), /* packet command (first stage) */
	REQ_IDETAPE_PC2		= (1 << 1), /* packet command (second stage) */
	REQ_IDETAPE_READ	= (1 << 2),
	REQ_IDETAPE_WRITE	= (1 << 3),
	REQ_IDETAPE_READ_BUFFER	= (1 << 4),
};

/*
 *	Error codes which are returned in rq->errors to the higher part
 *	of the driver.
 */
#define	IDETAPE_ERROR_GENERAL		101
#define	IDETAPE_ERROR_FILEMARK		102
#define	IDETAPE_ERROR_EOD		103

/*
 *	The following is used to format the general configuration word of
 *	the ATAPI IDENTIFY DEVICE command.
 */
struct idetape_id_gcw {	
	unsigned packet_size		:2;	/* Packet Size */
	unsigned reserved234		:3;	/* Reserved */
	unsigned drq_type		:2;	/* Command packet DRQ type */
	unsigned removable		:1;	/* Removable media */
	unsigned device_type		:5;	/* Device type */
	unsigned reserved13		:1;	/* Reserved */
	unsigned protocol		:2;	/* Protocol type */
};

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/* Structures related to the SELECT SENSE / MODE SENSE packet commands. */
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#define IDETAPE_BLOCK_DESCRIPTOR	0
#define	IDETAPE_CAPABILITIES_PAGE	0x2a

/*
 *	The variables below are used for the character device interface.
 *	Additional state variables are defined in our ide_drive_t structure.
 */
static struct ide_tape_obj * idetape_devs[MAX_HWIFS * MAX_DRIVES];

#define ide_tape_f(file) ((file)->private_data)

static struct ide_tape_obj *ide_tape_chrdev_get(unsigned int i)
{
	struct ide_tape_obj *tape = NULL;

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	mutex_lock(&idetape_ref_mutex);
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	tape = idetape_devs[i];
	if (tape)
		kref_get(&tape->kref);
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	mutex_unlock(&idetape_ref_mutex);
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	return tape;
}

/*
 *      Function declarations
 *
 */
static int idetape_chrdev_release (struct inode *inode, struct file *filp);
static void idetape_write_release (ide_drive_t *drive, unsigned int minor);

/*
 * Too bad. The drive wants to send us data which we are not ready to accept.
 * Just throw it away.
 */
static void idetape_discard_data (ide_drive_t *drive, unsigned int bcount)
{
	while (bcount--)
		(void) HWIF(drive)->INB(IDE_DATA_REG);
}

static void idetape_input_buffers (ide_drive_t *drive, idetape_pc_t *pc, unsigned int bcount)
{
	struct idetape_bh *bh = pc->bh;
	int count;

	while (bcount) {
		if (bh == NULL) {
			printk(KERN_ERR "ide-tape: bh == NULL in "
				"idetape_input_buffers\n");
			idetape_discard_data(drive, bcount);
			return;
		}
		count = min((unsigned int)(bh->b_size - atomic_read(&bh->b_count)), bcount);
		HWIF(drive)->atapi_input_bytes(drive, bh->b_data + atomic_read(&bh->b_count), count);
		bcount -= count;
		atomic_add(count, &bh->b_count);
		if (atomic_read(&bh->b_count) == bh->b_size) {
			bh = bh->b_reqnext;
			if (bh)
				atomic_set(&bh->b_count, 0);
		}
	}
	pc->bh = bh;
}

static void idetape_output_buffers (ide_drive_t *drive, idetape_pc_t *pc, unsigned int bcount)
{
	struct idetape_bh *bh = pc->bh;
	int count;

	while (bcount) {
		if (bh == NULL) {
			printk(KERN_ERR "ide-tape: bh == NULL in "
				"idetape_output_buffers\n");
			return;
		}
		count = min((unsigned int)pc->b_count, (unsigned int)bcount);
		HWIF(drive)->atapi_output_bytes(drive, pc->b_data, count);
		bcount -= count;
		pc->b_data += count;
		pc->b_count -= count;
		if (!pc->b_count) {
			pc->bh = bh = bh->b_reqnext;
			if (bh) {
				pc->b_data = bh->b_data;
				pc->b_count = atomic_read(&bh->b_count);
			}
		}
	}
}

static void idetape_update_buffers (idetape_pc_t *pc)
{
	struct idetape_bh *bh = pc->bh;
	int count;
	unsigned int bcount = pc->actually_transferred;

	if (test_bit(PC_WRITING, &pc->flags))
		return;
	while (bcount) {
		if (bh == NULL) {
			printk(KERN_ERR "ide-tape: bh == NULL in "
				"idetape_update_buffers\n");
			return;
		}
		count = min((unsigned int)bh->b_size, (unsigned int)bcount);
		atomic_set(&bh->b_count, count);
		if (atomic_read(&bh->b_count) == bh->b_size)
			bh = bh->b_reqnext;
		bcount -= count;
	}
	pc->bh = bh;
}

/*
 *	idetape_next_pc_storage returns a pointer to a place in which we can
 *	safely store a packet command, even though we intend to leave the
 *	driver. A storage space for a maximum of IDETAPE_PC_STACK packet
 *	commands is allocated at initialization time.
 */
static idetape_pc_t *idetape_next_pc_storage (ide_drive_t *drive)
{
	idetape_tape_t *tape = drive->driver_data;

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	debug_log(DBG_PCRQ_STACK, "pc_stack_index=%d\n", tape->pc_stack_index);

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	if (tape->pc_stack_index == IDETAPE_PC_STACK)
		tape->pc_stack_index=0;
	return (&tape->pc_stack[tape->pc_stack_index++]);
}

/*
 *	idetape_next_rq_storage is used along with idetape_next_pc_storage.
 *	Since we queue packet commands in the request queue, we need to
 *	allocate a request, along with the allocation of a packet command.
 */
 
/**************************************************************
 *                                                            *
 *  This should get fixed to use kmalloc(.., GFP_ATOMIC)      *
 *  followed later on by kfree().   -ml                       *
 *                                                            *
 **************************************************************/
 
static struct request *idetape_next_rq_storage (ide_drive_t *drive)
{
	idetape_tape_t *tape = drive->driver_data;

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	debug_log(DBG_PCRQ_STACK, "rq_stack_index=%d\n", tape->rq_stack_index);

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	if (tape->rq_stack_index == IDETAPE_PC_STACK)
		tape->rq_stack_index=0;
	return (&tape->rq_stack[tape->rq_stack_index++]);
}

/*
 *	idetape_init_pc initializes a packet command.
 */
static void idetape_init_pc (idetape_pc_t *pc)
{
	memset(pc->c, 0, 12);
	pc->retries = 0;
	pc->flags = 0;
	pc->request_transfer = 0;
	pc->buffer = pc->pc_buffer;
	pc->buffer_size = IDETAPE_PC_BUFFER_SIZE;
	pc->bh = NULL;
	pc->b_data = NULL;
}

/*
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 * called on each failed packet command retry to analyze the request sense. We
 * currently do not utilize this information.
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 */
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static void idetape_analyze_error(ide_drive_t *drive, u8 *sense)
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{
	idetape_tape_t *tape = drive->driver_data;
	idetape_pc_t *pc = tape->failed_pc;

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	tape->sense_key = sense[2] & 0xF;
	tape->asc       = sense[12];
	tape->ascq      = sense[13];
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	debug_log(DBG_ERR, "pc = %x, sense key = %x, asc = %x, ascq = %x\n",
		 pc->c[0], tape->sense_key, tape->asc, tape->ascq);
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	/* Correct pc->actually_transferred by asking the tape.	 */
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	if (test_bit(PC_DMA_ERROR, &pc->flags)) {
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		pc->actually_transferred = pc->request_transfer -
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			tape->blk_size *
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			be32_to_cpu(get_unaligned((u32 *)&sense[3]));
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		idetape_update_buffers(pc);
	}

	/*
	 * If error was the result of a zero-length read or write command,
	 * with sense key=5, asc=0x22, ascq=0, let it slide.  Some drives
	 * (i.e. Seagate STT3401A Travan) don't support 0-length read/writes.
	 */
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	if ((pc->c[0] == READ_6 || pc->c[0] == WRITE_6)
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	    /* length == 0 */
	    && pc->c[4] == 0 && pc->c[3] == 0 && pc->c[2] == 0) {
		if (tape->sense_key == 5) {
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			/* don't report an error, everything's ok */
			pc->error = 0;
			/* don't retry read/write */
			set_bit(PC_ABORT, &pc->flags);
		}
	}
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	if (pc->c[0] == READ_6 && (sense[2] & 0x80)) {
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		pc->error = IDETAPE_ERROR_FILEMARK;
		set_bit(PC_ABORT, &pc->flags);
	}
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	if (pc->c[0] == WRITE_6) {
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		if ((sense[2] & 0x40) || (tape->sense_key == 0xd
		     && tape->asc == 0x0 && tape->ascq == 0x2)) {
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			pc->error = IDETAPE_ERROR_EOD;
			set_bit(PC_ABORT, &pc->flags);
		}
	}
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	if (pc->c[0] == READ_6 || pc->c[0] == WRITE_6) {
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		if (tape->sense_key == 8) {
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			pc->error = IDETAPE_ERROR_EOD;
			set_bit(PC_ABORT, &pc->flags);
		}
		if (!test_bit(PC_ABORT, &pc->flags) &&
		    pc->actually_transferred)
			pc->retries = IDETAPE_MAX_PC_RETRIES + 1;
	}
}

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static void idetape_activate_next_stage(ide_drive_t *drive)
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{
	idetape_tape_t *tape = drive->driver_data;
	idetape_stage_t *stage = tape->next_stage;
	struct request *rq = &stage->rq;

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	debug_log(DBG_PROCS, "Enter %s\n", __func__);

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	if (stage == NULL) {
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		printk(KERN_ERR "ide-tape: bug: Trying to activate a non"
				" existing stage\n");
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		return;
	}

	rq->rq_disk = tape->disk;
	rq->buffer = NULL;
	rq->special = (void *)stage->bh;
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	tape->active_data_rq = rq;
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	tape->active_stage = stage;
	tape->next_stage = stage->next;
}

/*
 *	idetape_kfree_stage calls kfree to completely free a stage, along with
 *	its related buffers.
 */
static void __idetape_kfree_stage (idetape_stage_t *stage)
{
	struct idetape_bh *prev_bh, *bh = stage->bh;
	int size;

	while (bh != NULL) {
		if (bh->b_data != NULL) {
			size = (int) bh->b_size;
			while (size > 0) {
				free_page((unsigned long) bh->b_data);
				size -= PAGE_SIZE;
				bh->b_data += PAGE_SIZE;
			}
		}
		prev_bh = bh;
		bh = bh->b_reqnext;
		kfree(prev_bh);
	}
	kfree(stage);
}

static void idetape_kfree_stage (idetape_tape_t *tape, idetape_stage_t *stage)
{
	__idetape_kfree_stage(stage);
}

/*
 *	idetape_remove_stage_head removes tape->first_stage from the pipeline.
 *	The caller should avoid race conditions.
 */
static void idetape_remove_stage_head (ide_drive_t *drive)
{
	idetape_tape_t *tape = drive->driver_data;
	idetape_stage_t *stage;
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	debug_log(DBG_PROCS, "Enter %s\n", __func__);

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	if (tape->first_stage == NULL) {
		printk(KERN_ERR "ide-tape: bug: tape->first_stage is NULL\n");
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		return;
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	}
	if (tape->active_stage == tape->first_stage) {
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		printk(KERN_ERR "ide-tape: bug: Trying to free our active "
				"pipeline stage\n");
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		return;
	}
	stage = tape->first_stage;
	tape->first_stage = stage->next;
	idetape_kfree_stage(tape, stage);
	tape->nr_stages--;
	if (tape->first_stage == NULL) {
		tape->last_stage = NULL;
		if (tape->next_stage != NULL)
			printk(KERN_ERR "ide-tape: bug: tape->next_stage != NULL\n");
		if (tape->nr_stages)
			printk(KERN_ERR "ide-tape: bug: nr_stages should be 0 now\n");
	}
}

/*
 * This will free all the pipeline stages starting from new_last_stage->next
 * to the end of the list, and point tape->last_stage to new_last_stage.
 */
static void idetape_abort_pipeline(ide_drive_t *drive,
				   idetape_stage_t *new_last_stage)
{
	idetape_tape_t *tape = drive->driver_data;
	idetape_stage_t *stage = new_last_stage->next;
	idetape_stage_t *nstage;

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	debug_log(DBG_PROCS, "%s: Enter %s\n", tape->name, __func__);

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	while (stage) {
		nstage = stage->next;
		idetape_kfree_stage(tape, stage);
		--tape->nr_stages;
		--tape->nr_pending_stages;
		stage = nstage;
	}
	if (new_last_stage)
		new_last_stage->next = NULL;
	tape->last_stage = new_last_stage;
	tape->next_stage = NULL;
}

/*
 *	idetape_end_request is used to finish servicing a request, and to
 *	insert a pending pipeline request into the main device queue.
 */
static int idetape_end_request(ide_drive_t *drive, int uptodate, int nr_sects)
{
	struct request *rq = HWGROUP(drive)->rq;
	idetape_tape_t *tape = drive->driver_data;
	unsigned long flags;
	int error;
	int remove_stage = 0;
	idetape_stage_t *active_stage;

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	debug_log(DBG_PROCS, "Enter %s\n", __func__);
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	switch (uptodate) {
		case 0:	error = IDETAPE_ERROR_GENERAL; break;
		case 1: error = 0; break;
		default: error = uptodate;
	}
	rq->errors = error;
	if (error)
		tape->failed_pc = NULL;

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	if (!blk_special_request(rq)) {
		ide_end_request(drive, uptodate, nr_sects);
		return 0;
	}

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	spin_lock_irqsave(&tape->lock, flags);
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	/* The request was a pipelined data transfer request */
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	if (tape->active_data_rq == rq) {
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		active_stage = tape->active_stage;
		tape->active_stage = NULL;
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		tape->active_data_rq = NULL;
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		tape->nr_pending_stages--;
		if (rq->cmd[0] & REQ_IDETAPE_WRITE) {
			remove_stage = 1;
			if (error) {
				set_bit(IDETAPE_PIPELINE_ERROR, &tape->flags);
				if (error == IDETAPE_ERROR_EOD)
					idetape_abort_pipeline(drive, active_stage);
			}
		} else if (rq->cmd[0] & REQ_IDETAPE_READ) {
			if (error == IDETAPE_ERROR_EOD) {
				set_bit(IDETAPE_PIPELINE_ERROR, &tape->flags);
				idetape_abort_pipeline(drive, active_stage);
			}
		}
		if (tape->next_stage != NULL) {
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			idetape_activate_next_stage(drive);
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			/*
			 * Insert the next request into the request queue.
			 */
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			(void)ide_do_drive_cmd(drive, tape->active_data_rq,
						ide_end);
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		} else if (!error) {
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			/*
			 * This is a part of the feedback loop which tries to
			 * find the optimum number of stages. We are starting
			 * from a minimum maximum number of stages, and if we
			 * sense that the pipeline is empty, we try to increase
			 * it, until we reach the user compile time memory
			 * limit.
			 */
			int i = (tape->max_pipeline - tape->min_pipeline) / 10;

			tape->max_stages += max(i, 1);
			tape->max_stages = max(tape->max_stages,
						tape->min_pipeline);
			tape->max_stages = min(tape->max_stages,
						tape->max_pipeline);
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		}
	}
	ide_end_drive_cmd(drive, 0, 0);
//	blkdev_dequeue_request(rq);
//	drive->rq = NULL;
//	end_that_request_last(rq);

	if (remove_stage)
		idetape_remove_stage_head(drive);
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	if (tape->active_data_rq == NULL)
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		clear_bit(IDETAPE_PIPELINE_ACTIVE, &tape->flags);
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	spin_unlock_irqrestore(&tape->lock, flags);
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	return 0;
}

static ide_startstop_t idetape_request_sense_callback (ide_drive_t *drive)
{
	idetape_tape_t *tape = drive->driver_data;

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	debug_log(DBG_PROCS, "Enter %s\n", __func__);

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	if (!tape->pc->error) {
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		idetape_analyze_error(drive, tape->pc->buffer);
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		idetape_end_request(drive, 1, 0);
	} else {
		printk(KERN_ERR "ide-tape: Error in REQUEST SENSE itself - Aborting request!\n");
		idetape_end_request(drive, 0, 0);
	}
	return ide_stopped;
}

static void idetape_create_request_sense_cmd (idetape_pc_t *pc)
{
	idetape_init_pc(pc);	
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	pc->c[0] = REQUEST_SENSE;
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	pc->c[4] = 20;
	pc->request_transfer = 20;
	pc->callback = &idetape_request_sense_callback;
}

static void idetape_init_rq(struct request *rq, u8 cmd)
{
	memset(rq, 0, sizeof(*rq));
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	rq->cmd_type = REQ_TYPE_SPECIAL;
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	rq->cmd[0] = cmd;
}

/*
 *	idetape_queue_pc_head generates a new packet command request in front
 *	of the request queue, before the current request, so that it will be
 *	processed immediately, on the next pass through the driver.
 *
 *	idetape_queue_pc_head is called from the request handling part of
 *	the driver (the "bottom" part). Safe storage for the request should
 *	be allocated with idetape_next_pc_storage and idetape_next_rq_storage
 *	before calling idetape_queue_pc_head.
 *
 *	Memory for those requests is pre-allocated at initialization time, and
 *	is limited to IDETAPE_PC_STACK requests. We assume that we have enough
 *	space for the maximum possible number of inter-dependent packet commands.
 *
 *	The higher level of the driver - The ioctl handler and the character
 *	device handling functions should queue request to the lower level part
 *	and wait for their completion using idetape_queue_pc_tail or
 *	idetape_queue_rw_tail.
 */
static void idetape_queue_pc_head (ide_drive_t *drive, idetape_pc_t *pc,struct request *rq)
{
	struct ide_tape_obj *tape = drive->driver_data;

	idetape_init_rq(rq, REQ_IDETAPE_PC1);
	rq->buffer = (char *) pc;
	rq->rq_disk = tape->disk;
	(void) ide_do_drive_cmd(drive, rq, ide_preempt);
}

/*
 *	idetape_retry_pc is called when an error was detected during the
 *	last packet command. We queue a request sense packet command in
 *	the head of the request list.
 */
static ide_startstop_t idetape_retry_pc (ide_drive_t *drive)
{
	idetape_tape_t *tape = drive->driver_data;
	idetape_pc_t *pc;
	struct request *rq;

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	(void)ide_read_error(drive);
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	pc = idetape_next_pc_storage(drive);
	rq = idetape_next_rq_storage(drive);
	idetape_create_request_sense_cmd(pc);
	set_bit(IDETAPE_IGNORE_DSC, &tape->flags);
	idetape_queue_pc_head(drive, pc, rq);
	return ide_stopped;
}

/*
 *	idetape_postpone_request postpones the current request so that
 *	ide.c will be able to service requests from another device on
 *	the same hwgroup while we are polling for DSC.
 */
static void idetape_postpone_request (ide_drive_t *drive)
{
	idetape_tape_t *tape = drive->driver_data;

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	debug_log(DBG_PROCS, "Enter %s\n", __func__);

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	tape->postponed_rq = HWGROUP(drive)->rq;
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	ide_stall_queue(drive, tape->dsc_poll_freq);
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}

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typedef void idetape_io_buf(ide_drive_t *, idetape_pc_t *, unsigned int);

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/*
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 * This is the usual interrupt handler which will be called during a packet
 * command. We will transfer some of the data (as requested by the drive) and
 * will re-point interrupt handler to us. When data transfer is finished, we
 * will act according to the algorithm described before
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 * idetape_issue_pc.
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 */
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static ide_startstop_t idetape_pc_intr(ide_drive_t *drive)
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{
	ide_hwif_t *hwif = drive->hwif;
	idetape_tape_t *tape = drive->driver_data;
	idetape_pc_t *pc = tape->pc;
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	xfer_func_t *xferfunc;
	idetape_io_buf *iobuf;
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	unsigned int temp;
#if SIMULATE_ERRORS
	static int error_sim_count = 0;
#endif
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	u16 bcount;
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	u8 stat, ireason;
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	debug_log(DBG_PROCS, "Enter %s - interrupt handler\n", __func__);
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	/* Clear the interrupt */
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	stat = ide_read_status(drive);
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	if (test_bit(PC_DMA_IN_PROGRESS, &pc->flags)) {
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		if (hwif->ide_dma_end(drive) || (stat & ERR_STAT)) {
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			/*
			 * A DMA error is sometimes expected. For example,
			 * if the tape is crossing a filemark during a
			 * READ command, it will issue an irq and position
			 * itself before the filemark, so that only a partial
			 * data transfer will occur (which causes the DMA
			 * error). In that case, we will later ask the tape
			 * how much bytes of the original request were
			 * actually transferred (we can't receive that
			 * information from the DMA engine on most chipsets).
			 */

			/*
			 * On the contrary, a DMA error is never expected;
			 * it usually indicates a hardware error or abort.
			 * If the tape crosses a filemark during a READ
			 * command, it will issue an irq and position itself
			 * after the filemark (not before). Only a partial
			 * data transfer will occur, but no DMA error.
			 * (AS, 19 Apr 2001)
			 */
			set_bit(PC_DMA_ERROR, &pc->flags);
		} else {
			pc->actually_transferred = pc->request_transfer;
			idetape_update_buffers(pc);
		}
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		debug_log(DBG_PROCS, "DMA finished\n");

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	}

	/* No more interrupts */
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	if ((stat & DRQ_STAT) == 0) {
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		debug_log(DBG_SENSE, "Packet command completed, %d bytes"
				" transferred\n", pc->actually_transferred);
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		clear_bit(PC_DMA_IN_PROGRESS, &pc->flags);
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		local_irq_enable();

#if SIMULATE_ERRORS
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		if ((pc->c[0] == WRITE_6 || pc->c[0] == READ_6) &&
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		    (++error_sim_count % 100) == 0) {
			printk(KERN_INFO "ide-tape: %s: simulating error\n",
				tape->name);
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			stat |= ERR_STAT;
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		}
#endif
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		if ((stat & ERR_STAT) && pc->c[0] == REQUEST_SENSE)
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			stat &= ~ERR_STAT;
		if ((stat & ERR_STAT) || test_bit(PC_DMA_ERROR, &pc->flags)) {
			/* Error detected */
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			debug_log(DBG_ERR, "%s: I/O error\n", tape->name);

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			if (pc->c[0] == REQUEST_SENSE) {
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				printk(KERN_ERR "ide-tape: I/O error in request"
						" sense command\n");
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				return ide_do_reset(drive);
			}
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			debug_log(DBG_ERR, "[cmd %x]: check condition\n",
					pc->c[0]);

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			/* Retry operation */
			return idetape_retry_pc(drive);
		}
		pc->error = 0;
		if (test_bit(PC_WAIT_FOR_DSC, &pc->flags) &&
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		    (stat & SEEK_STAT) == 0) {
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			/* Media access command */
			tape->dsc_polling_start = jiffies;
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			tape->dsc_poll_freq = IDETAPE_DSC_MA_FAST;
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			tape->dsc_timeout = jiffies + IDETAPE_DSC_MA_TIMEOUT;
			/* Allow ide.c to handle other requests */
			idetape_postpone_request(drive);
			return ide_stopped;
		}
		if (tape->failed_pc == pc)
			tape->failed_pc = NULL;
		/* Command finished - Call the callback function */
		return pc->callback(drive);
	}
	if (test_and_clear_bit(PC_DMA_IN_PROGRESS, &pc->flags)) {
		printk(KERN_ERR "ide-tape: The tape wants to issue more "
				"interrupts in DMA mode\n");
		printk(KERN_ERR "ide-tape: DMA disabled, reverting to PIO\n");
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		ide_dma_off(drive);
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		return ide_do_reset(drive);
	}
	/* Get the number of bytes to transfer on this interrupt. */
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	bcount = (hwif->INB(IDE_BCOUNTH_REG) << 8) |
		  hwif->INB(IDE_BCOUNTL_REG);
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	ireason = hwif->INB(IDE_IREASON_REG);
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	if (ireason & CD) {
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		printk(KERN_ERR "ide-tape: CoD != 0 in %s\n", __func__);
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		return ide_do_reset(drive);
	}
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	if (((ireason & IO) == IO) == test_bit(PC_WRITING, &pc->flags)) {
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		/* Hopefully, we will never get here */
		printk(KERN_ERR "ide-tape: We wanted to %s, ",
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				(ireason & IO) ? "Write" : "Read");
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		printk(KERN_ERR "ide-tape: but the tape wants us to %s !\n",
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				(ireason & IO) ? "Read" : "Write");
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		return ide_do_reset(drive);
	}
	if (!test_bit(PC_WRITING, &pc->flags)) {
		/* Reading - Check that we have enough space */
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		temp = pc->actually_transferred + bcount;
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		if (temp > pc->request_transfer) {
			if (temp > pc->buffer_size) {
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				printk(KERN_ERR "ide-tape: The tape wants to "
					"send us more data than expected "
					"- discarding data\n");
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				idetape_discard_data(drive, bcount);
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				ide_set_handler(drive, &idetape_pc_intr,
						IDETAPE_WAIT_CMD, NULL);
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				return ide_started;
			}
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			debug_log(DBG_SENSE, "The tape wants to send us more "
				"data than expected - allowing transfer\n");
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		}
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		iobuf = &idetape_input_buffers;
		xferfunc = hwif->atapi_input_bytes;
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	} else {
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		iobuf = &idetape_output_buffers;
		xferfunc = hwif->atapi_output_bytes;
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	}
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	if (pc->bh)
		iobuf(drive, pc, bcount);
	else
		xferfunc(drive, pc->current_position, bcount);

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	/* Update the current position */
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	pc->actually_transferred += bcount;
	pc->current_position += bcount;
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	debug_log(DBG_SENSE, "[cmd %x] transferred %d bytes on that intr.\n",
			pc->c[0], bcount);

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	/* And set the interrupt handler again */
	ide_set_handler(drive, &idetape_pc_intr, IDETAPE_WAIT_CMD, NULL);
	return ide_started;
}

/*
 *	Packet Command Interface
 *
 *	The current Packet Command is available in tape->pc, and will not
 *	change until we finish handling it. Each packet command is associated
 *	with a callback function that will be called when the command is
 *	finished.
 *
 *	The handling will be done in three stages:
 *
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 *	1.	idetape_issue_pc will send the packet command to the
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 *		drive, and will set the interrupt handler to idetape_pc_intr.
 *
 *	2.	On each interrupt, idetape_pc_intr will be called. This step
 *		will be repeated until the device signals us that no more
 *		interrupts will be issued.
 *
 *	3.	ATAPI Tape media access commands have immediate status with a
 *		delayed process. In case of a successful initiation of a
 *		media access packet command, the DSC bit will be set when the
 *		actual execution of the command is finished. 
 *		Since the tape drive will not issue an interrupt, we have to
 *		poll for this event. In this case, we define the request as
 *		"low priority request" by setting rq_status to
 *		IDETAPE_RQ_POSTPONED, 	set a timer to poll for DSC and exit
 *		the driver.
 *
 *		ide.c will then give higher priority to requests which
 *		originate from the other device, until will change rq_status
 *		to RQ_ACTIVE.
 *
 *	4.	When the packet command is finished, it will be checked for errors.
 *
 *	5.	In case an error was found, we queue a request sense packet
 *		command in front of the request queue and retry the operation
 *		up to IDETAPE_MAX_PC_RETRIES times.
 *
 *	6.	In case no error was found, or we decided to give up and not
 *		to retry again, the callback function will be called and then
 *		we will handle the next request.
 *
 */
static ide_startstop_t idetape_transfer_pc(ide_drive_t *drive)
{
	ide_hwif_t *hwif = drive->hwif;
	idetape_tape_t *tape = drive->driver_data;
	idetape_pc_t *pc = tape->pc;
	int retries = 100;
	ide_startstop_t startstop;
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	u8 ireason;
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	if (ide_wait_stat(&startstop,drive,DRQ_STAT,BUSY_STAT,WAIT_READY)) {
		printk(KERN_ERR "ide-tape: Strange, packet command initiated yet DRQ isn't asserted\n");
		return startstop;
	}
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	ireason = hwif->INB(IDE_IREASON_REG);
	while (retries-- && ((ireason & CD) == 0 || (ireason & IO))) {
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		printk(KERN_ERR "ide-tape: (IO,CoD != (0,1) while issuing "
				"a packet command, retrying\n");
		udelay(100);
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		ireason = hwif->INB(IDE_IREASON_REG);
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		if (retries == 0) {
			printk(KERN_ERR "ide-tape: (IO,CoD != (0,1) while "
					"issuing a packet command, ignoring\n");
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			ireason |= CD;
			ireason &= ~IO;
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		}
	}
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	if ((ireason & CD) == 0 || (ireason & IO)) {
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		printk(KERN_ERR "ide-tape: (IO,CoD) != (0,1) while issuing "
				"a packet command\n");
		return ide_do_reset(drive);
	}
	/* Set the interrupt routine */
	ide_set_handler(drive, &idetape_pc_intr, IDETAPE_WAIT_CMD, NULL);
#ifdef CONFIG_BLK_DEV_IDEDMA
	/* Begin DMA, if necessary */
	if (test_bit(PC_DMA_IN_PROGRESS, &pc->flags))
		hwif->dma_start(drive);
#endif
	/* Send the actual packet */
	HWIF(drive)->atapi_output_bytes(drive, pc->c, 12);
	return ide_started;
}

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static ide_startstop_t idetape_issue_pc(ide_drive_t *drive, idetape_pc_t *pc)
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{
	ide_hwif_t *hwif = drive->hwif;
	idetape_tape_t *tape = drive->driver_data;
	int dma_ok = 0;
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	u16 bcount;
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	if (tape->pc->c[0] == REQUEST_SENSE &&
	    pc->c[0] == REQUEST_SENSE) {
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		printk(KERN_ERR "ide-tape: possible ide-tape.c bug - "
			"Two request sense in serial were issued\n");
	}

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	if (tape->failed_pc == NULL && pc->c[0] != REQUEST_SENSE)
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		tape->failed_pc = pc;
	/* Set the current packet command */
	tape->pc = pc;

	if (pc->retries > IDETAPE_MAX_PC_RETRIES ||
	    test_bit(PC_ABORT, &pc->flags)) {
		/*
		 *	We will "abort" retrying a packet command in case
		 *	a legitimate error code was received (crossing a
		 *	filemark, or end of the media, for example).
		 */
		if (!test_bit(PC_ABORT, &pc->flags)) {
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			if (!(pc->c[0] == TEST_UNIT_READY &&
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			      tape->sense_key == 2 && tape->asc == 4 &&
			     (tape->ascq == 1 || tape->ascq == 8))) {
				printk(KERN_ERR "ide-tape: %s: I/O error, "
						"pc = %2x, key = %2x, "
						"asc = %2x, ascq = %2x\n",
						tape->name, pc->c[0],
						tape->sense_key, tape->asc,
						tape->ascq);
			}
			/* Giving up */
			pc->error = IDETAPE_ERROR_GENERAL;
		}
		tape->failed_pc = NULL;
		return pc->callback(drive);
	}
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	debug_log(DBG_SENSE, "Retry #%d, cmd = %02X\n", pc->retries, pc->c[0]);
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	pc->retries++;
	/* We haven't transferred any data yet */
	pc->actually_transferred = 0;
	pc->current_position = pc->buffer;
	/* Request to transfer the entire buffer at once */
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	bcount = pc->request_transfer;
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	if (test_and_clear_bit(PC_DMA_ERROR, &pc->flags)) {
		printk(KERN_WARNING "ide-tape: DMA disabled, "
				"reverting to PIO\n");
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		ide_dma_off(drive);
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	}
	if (test_bit(PC_DMA_RECOMMENDED, &pc->flags) && drive->using_dma)
		dma_ok = !hwif->dma_setup(drive);

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	ide_pktcmd_tf_load(drive, IDE_TFLAG_NO_SELECT_MASK |
			   IDE_TFLAG_OUT_DEVICE, bcount, dma_ok);

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	if (dma_ok)			/* Will begin DMA later */
		set_bit(PC_DMA_IN_PROGRESS, &pc->flags);
	if (test_bit(IDETAPE_DRQ_INTERRUPT, &tape->flags)) {
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		ide_execute_command(drive, WIN_PACKETCMD, &idetape_transfer_pc,
				    IDETAPE_WAIT_CMD, NULL);
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		return ide_started;
	} else {
		hwif->OUTB(WIN_PACKETCMD, IDE_COMMAND_REG);
		return idetape_transfer_pc(drive);
	}
}

/*
 *	General packet command callback function.
 */
static ide_startstop_t idetape_pc_callback (ide_drive_t *drive)
{
	idetape_tape_t *tape = drive->driver_data;
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	debug_log(DBG_PROCS, "Enter %s\n", __func__);
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	idetape_end_request(drive, tape->pc->error ? 0 : 1, 0);
	return ide_stopped;
}

/*
 *	A mode sense command is used to "sense" tape parameters.
 */
static void idetape_create_mode_sense_cmd (idetape_pc_t *pc, u8 page_code)
{
	idetape_init_pc(pc);
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	pc->c[0] = MODE_SENSE;
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	if (page_code != IDETAPE_BLOCK_DESCRIPTOR)
		pc->c[1] = 8;	/* DBD = 1 - Don't return block descriptors */
	pc->c[2] = page_code;
	/*
	 * Changed pc->c[3] to 0 (255 will at best return unused info).
	 *
	 * For SCSI this byte is defined as subpage instead of high byte
	 * of length and some IDE drives seem to interpret it this way
	 * and return an error when 255 is used.
	 */
	pc->c[3] = 0;
	pc->c[4] = 255;		/* (We will just discard data in that case) */
	if (page_code == IDETAPE_BLOCK_DESCRIPTOR)
		pc->request_transfer = 12;
	else if (page_code == IDETAPE_CAPABILITIES_PAGE)
		pc->request_transfer = 24;
	else
		pc->request_transfer = 50;
	pc->callback = &idetape_pc_callback;
}

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static void idetape_calculate_speeds(ide_drive_t *drive)
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{
	idetape_tape_t *tape = drive->driver_data;

	if (time_after(jiffies, tape->controlled_pipeline_head_time + 120 * HZ)) {
		tape->controlled_previous_pipeline_head = tape->controlled_last_pipeline_head;
		tape->controlled_previous_head_time = tape->controlled_pipeline_head_time;
		tape->controlled_last_pipeline_head = tape->pipeline_head;
		tape->controlled_pipeline_head_time = jiffies;
	}
	if (time_after(jiffies, tape->controlled_pipeline_head_time + 60 * HZ))
		tape->controlled_pipeline_head_speed = (tape->pipeline_head - tape->controlled_last_pipeline_head) * 32 * HZ / (jiffies - tape->controlled_pipeline_head_time);
	else if (time_after(jiffies, tape->controlled_previous_head_time))
		tape->controlled_pipeline_head_speed = (tape->pipeline_head - tape->controlled_previous_pipeline_head) * 32 * HZ / (jiffies - tape->controlled_previous_head_time);

	if (tape->nr_pending_stages < tape->max_stages /*- 1 */) {
		/* -1 for read mode error recovery */
		if (time_after(jiffies, tape->uncontrolled_previous_head_time + 10 * HZ)) {
			tape->uncontrolled_pipeline_head_time = jiffies;
			tape->uncontrolled_pipeline_head_speed = (tape->pipeline_head - tape->uncontrolled_previous_pipeline_head) * 32 * HZ / (jiffies - tape->uncontrolled_previous_head_time);
		}
	} else {
		tape->uncontrolled_previous_head_time = jiffies;
		tape->uncontrolled_previous_pipeline_head = tape->pipeline_head;
		if (time_after(jiffies, tape->uncontrolled_pipeline_head_time + 30 * HZ)) {
			tape->uncontrolled_pipeline_head_time = jiffies;
		}
	}
	tape->pipeline_head_speed = max(tape->uncontrolled_pipeline_head_speed, tape->controlled_pipeline_head_speed);
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	if (tape->speed_control == 1) {
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		if (tape->nr_pending_stages >= tape->max_stages / 2)
			tape->max_insert_speed = tape->pipeline_head_speed +
				(1100 - tape->pipeline_head_speed) * 2 * (tape->nr_pending_stages - tape->max_stages / 2) / tape->max_stages;
		else
			tape->max_insert_speed = 500 +
				(tape->pipeline_head_speed - 500) * 2 * tape->nr_pending_stages / tape->max_stages;
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		if (tape->nr_pending_stages >= tape->max_stages * 99 / 100)
			tape->max_insert_speed = 5000;
	} else
		tape->max_insert_speed = tape->speed_control;
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	tape->max_insert_speed = max(tape->max_insert_speed, 500);
}

static ide_startstop_t idetape_media_access_finished (ide_drive_t *drive)
{
	idetape_tape_t *tape = drive->driver_data;
	idetape_pc_t *pc = tape->pc;
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	u8 stat;
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	stat = ide_read_status(drive);

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	if (stat & SEEK_STAT) {
		if (stat & ERR_STAT) {
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			/* Error detected */
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			if (pc->c[0] != TEST_UNIT_READY)
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				printk(KERN_ERR "ide-tape: %s: I/O error, ",
						tape->name);
			/* Retry operation */
			return idetape_retry_pc(drive);
		}
		pc->error = 0;
		if (tape->failed_pc == pc)
			tape->failed_pc = NULL;
	} else {
		pc->error = IDETAPE_ERROR_GENERAL;
		tape->failed_pc = NULL;
	}
	return pc->callback(drive);
}

static ide_startstop_t idetape_rw_callback (ide_drive_t *drive)
{
	idetape_tape_t *tape = drive->driver_data;
	struct request *rq = HWGROUP(drive)->rq;
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	int blocks = tape->pc->actually_transferred / tape->blk_size;
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	tape->avg_size += blocks * tape->blk_size;
	tape->insert_size += blocks * tape->blk_size;
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	if (tape->insert_size > 1024 * 1024)
		tape->measure_insert_time = 1;
	if (tape->measure_insert_time) {
		tape->measure_insert_time = 0;
		tape->insert_time = jiffies;
		tape->insert_size = 0;
	}
	if (time_after(jiffies, tape->insert_time))
		tape->insert_speed = tape->insert_size / 1024 * HZ / (jiffies - tape->insert_time);
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	if (time_after_eq(jiffies, tape->avg_time + HZ)) {
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		tape->avg_speed = tape->avg_size * HZ / (jiffies - tape->avg_time) / 1024;
		tape->avg_size = 0;
		tape->avg_time = jiffies;
	}
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	debug_log(DBG_PROCS, "Enter %s\n", __func__);
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	tape->first_frame += blocks;
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	rq->curr