Linux-2.6.12-rc2v2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 4937 insertions, 0 deletions

diff --git a/drivers/ide/ide-tape.c b/drivers/ide/ide-tape.c
new file mode 100644
index 00000000000..48254485498
--- /dev/null
+++ b/drivers/ide/ide-tape.c
@@ -0,0 +1,4937 @@
+/*
+ * linux/drivers/ide/ide-tape.c		Version 1.19	Nov, 2003
+ *
+ * Copyright (C) 1995 - 1999 Gadi Oxman <gadio@netvision.net.il>
+ *
+ * $Header$
+ *
+ * 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).
+ */
+ 
+/*
+ * IDE ATAPI streaming tape driver.
+ *
+ * This driver is a part of the Linux ide driver and works in co-operation
+ * with linux/drivers/block/ide.c.
+ *
+ * The driver, in co-operation with ide.c, basically traverses the 
+ * request-list for the block device interface. The character device
+ * interface, on the other hand, creates new requests, adds them
+ * to the request-list of the block device, and waits for their completion.
+ *
+ * Pipelined operation mode is now supported on both reads and writes.
+ *
+ * The block device major and minor numbers are determined from the
+ * tape's relative position in the ide interfaces, as explained in ide.c.
+ *
+ * The character device interface consists of the following devices:
+ *
+ * ht0		major 37, minor 0	first  IDE tape, rewind on close.
+ * ht1		major 37, minor 1	second IDE tape, rewind on close.
+ * ...
+ * nht0		major 37, minor 128	first  IDE tape, no rewind on close.
+ * nht1		major 37, minor 129	second IDE tape, no rewind on close.
+ * ...
+ *
+ * Run linux/scripts/MAKEDEV.ide to create the above entries.
+ *
+ * The general magnetic tape commands compatible interface, as defined by
+ * include/linux/mtio.h, is accessible through the character device.
+ *
+ * General ide driver configuration options, such as the interrupt-unmask
+ * flag, can be configured by issuing an ioctl to the block device interface,
+ * as any other ide device.
+ *
+ * Our own ide-tape ioctl's can be issued to either the block device or
+ * the character device interface.
+ *
+ * Maximal throughput with minimal bus load will usually be achieved in the
+ * following scenario:
+ *
+ *	1.	ide-tape is operating in the pipelined operation mode.
+ *	2.	No buffering is performed by the user backup program.
+ *
+ * Testing was done with a 2 GB CONNER CTMA 4000 IDE ATAPI Streaming Tape Drive.
+ * 
+ * Ver 0.1   Nov  1 95   Pre-working code :-)
+ * Ver 0.2   Nov 23 95   A short backup (few megabytes) and restore procedure
+ *                        was successful ! (Using tar cvf ... on the block
+ *                        device interface).
+ *                       A longer backup resulted in major swapping, bad
+ *                        overall Linux performance and eventually failed as
+ *                        we received non serial read-ahead requests from the
+ *                        buffer cache.
+ * Ver 0.3   Nov 28 95   Long backups are now possible, thanks to the
+ *                        character device interface. Linux's responsiveness
+ *                        and performance doesn't seem to be much affected
+ *                        from the background backup procedure.
+ *                       Some general mtio.h magnetic tape operations are
+ *                        now supported by our character device. As a result,
+ *                        popular tape utilities are starting to work with
+ *                        ide tapes :-)
+ *                       The following configurations were tested:
+ *                       	1. An IDE ATAPI TAPE shares the same interface
+ *                       	   and irq with an IDE ATAPI CDROM.
+ *                        	2. An IDE ATAPI TAPE shares the same interface
+ *                          	   and irq with a normal IDE disk.
+ *                        Both configurations seemed to work just fine !
+ *                        However, to be on the safe side, it is meanwhile
+ *                        recommended to give the IDE TAPE its own interface
+ *                        and irq.
+ *                       The one thing which needs to be done here is to
+ *                        add a "request postpone" feature to ide.c,
+ *                        so that we won't have to wait for the tape to finish
+ *                        performing a long media access (DSC) request (such
+ *                        as a rewind) before we can access the other device
+ *                        on the same interface. This effect doesn't disturb
+ *                        normal operation most of the time because read/write
+ *                        requests are relatively fast, and once we are
+ *                        performing one tape r/w request, a lot of requests
+ *                        from the other device can be queued and ide.c will
+ *			  service all of them after this single tape request.
+ * Ver 1.0   Dec 11 95   Integrated into Linux 1.3.46 development tree.
+ *                       On each read / write request, we now ask the drive
+ *                        if we can transfer a constant number of bytes
+ *                        (a parameter of the drive) only to its buffers,
+ *                        without causing actual media access. If we can't,
+ *                        we just wait until we can by polling the DSC bit.
+ *                        This ensures that while we are not transferring
+ *                        more bytes than the constant referred to above, the
+ *                        interrupt latency will not become too high and
+ *                        we won't cause an interrupt timeout, as happened
+ *                        occasionally in the previous version.
+ *                       While polling for DSC, the current request is
+ *                        postponed and ide.c is free to handle requests from
+ *                        the other device. This is handled transparently to
+ *                        ide.c. The hwgroup locking method which was used
+ *                        in the previous version was removed.
+ *                       Use of new general features which are provided by
+ *                        ide.c for use with atapi devices.
+ *                        (Programming done by Mark Lord)
+ *                       Few potential bug fixes (Again, suggested by Mark)
+ *                       Single character device data transfers are now
+ *                        not limited in size, as they were before.
+ *                       We are asking the tape about its recommended
+ *                        transfer unit and send a larger data transfer
+ *                        as several transfers of the above size.
+ *                        For best results, use an integral number of this
+ *                        basic unit (which is shown during driver
+ *                        initialization). I will soon add an ioctl to get
+ *                        this important parameter.
+ *                       Our data transfer buffer is allocated on startup,
+ *                        rather than before each data transfer. This should
+ *                        ensure that we will indeed have a data buffer.
+ * Ver 1.1   Dec 14 95   Fixed random problems which occurred when the tape
+ *                        shared an interface with another device.
+ *                        (poll_for_dsc was a complete mess).
+ *                       Removed some old (non-active) code which had
+ *                        to do with supporting buffer cache originated
+ *                        requests.
+ *                       The block device interface can now be opened, so
+ *                        that general ide driver features like the unmask
+ *                        interrupts flag can be selected with an ioctl.
+ *                        This is the only use of the block device interface.
+ *                       New fast pipelined operation mode (currently only on
+ *                        writes). When using the pipelined mode, the
+ *                        throughput can potentially reach the maximum
+ *                        tape supported throughput, regardless of the
+ *                        user backup program. On my tape drive, it sometimes
+ *                        boosted performance by a factor of 2. Pipelined
+ *                        mode is enabled by default, but since it has a few
+ *                        downfalls as well, you may want to disable it.
+ *                        A short explanation of the pipelined operation mode
+ *                        is available below.
+ * Ver 1.2   Jan  1 96   Eliminated pipelined mode race condition.
+ *                       Added pipeline read mode. As a result, restores
+ *                        are now as fast as backups.
+ *                       Optimized shared interface behavior. The new behavior
+ *                        typically results in better IDE bus efficiency and
+ *                        higher tape throughput.
+ *                       Pre-calculation of the expected read/write request
+ *                        service time, based on the tape's parameters. In
+ *                        the pipelined operation mode, this allows us to
+ *                        adjust our polling frequency to a much lower value,
+ *                        and thus to dramatically reduce our load on Linux,
+ *                        without any decrease in performance.
+ *                       Implemented additional mtio.h operations.
+ *                       The recommended user block size is returned by
+ *                        the MTIOCGET ioctl.
+ *                       Additional minor changes.
+ * Ver 1.3   Feb  9 96   Fixed pipelined read mode bug which prevented the
+ *                        use of some block sizes during a restore procedure.
+ *                       The character device interface will now present a
+ *                        continuous view of the media - any mix of block sizes
+ *                        during a backup/restore procedure is supported. The
+ *                        driver will buffer the requests internally and
+ *                        convert them to the tape's recommended transfer
+ *                        unit, making performance almost independent of the
+ *                        chosen user block size.
+ *                       Some improvements in error recovery.
+ *                       By cooperating with ide-dma.c, bus mastering DMA can
+ *                        now sometimes be used with IDE tape drives as well.
+ *                        Bus mastering DMA has the potential to dramatically
+ *                        reduce the CPU's overhead when accessing the device,
+ *                        and can be enabled by using hdparm -d1 on the tape's
+ *                        block device interface. For more info, read the
+ *                        comments in ide-dma.c.
+ * Ver 1.4   Mar 13 96   Fixed serialize support.
+ * Ver 1.5   Apr 12 96   Fixed shared interface operation, broken in 1.3.85.
+ *                       Fixed pipelined read mode inefficiency.
+ *                       Fixed nasty null dereferencing bug.
+ * Ver 1.6   Aug 16 96   Fixed FPU usage in the driver.
+ *                       Fixed end of media bug.
+ * Ver 1.7   Sep 10 96   Minor changes for the CONNER CTT8000-A model.
+ * Ver 1.8   Sep 26 96   Attempt to find a better balance between good
+ *                        interactive response and high system throughput.
+ * Ver 1.9   Nov  5 96   Automatically cross encountered filemarks rather
+ *                        than requiring an explicit FSF command.
+ *                       Abort pending requests at end of media.
+ *                       MTTELL was sometimes returning incorrect results.
+ *                       Return the real block size in the MTIOCGET ioctl.
+ *                       Some error recovery bug fixes.
+ * Ver 1.10  Nov  5 96   Major reorganization.
+ *                       Reduced CPU overhead a bit by eliminating internal
+ *                        bounce buffers.
+ *                       Added module support.
+ *                       Added multiple tape drives support.
+ *                       Added partition support.
+ *                       Rewrote DSC handling.
+ *                       Some portability fixes.
+ *                       Removed ide-tape.h.
+ *                       Additional minor changes.
+ * Ver 1.11  Dec  2 96   Bug fix in previous DSC timeout handling.
+ *                       Use ide_stall_queue() for DSC overlap.
+ *                       Use the maximum speed rather than the current speed
+ *                        to compute the request service time.
+ * Ver 1.12  Dec  7 97   Fix random memory overwriting and/or last block data
+ *                        corruption, which could occur if the total number
+ *                        of bytes written to the tape was not an integral
+ *                        number of tape blocks.
+ *                       Add support for INTERRUPT DRQ devices.
+ * Ver 1.13  Jan  2 98   Add "speed == 0" work-around for HP COLORADO 5GB
+ * Ver 1.14  Dec 30 98   Partial fixes for the Sony/AIWA tape drives.
+ *                       Replace cli()/sti() with hwgroup spinlocks.
+ * Ver 1.15  Mar 25 99   Fix SMP race condition by replacing hwgroup
+ *                        spinlock with private per-tape spinlock.
+ * Ver 1.16  Sep  1 99   Add OnStream tape support.
+ *                       Abort read pipeline on EOD.
+ *                       Wait for the tape to become ready in case it returns
+ *                        "in the process of becoming ready" on open().
+ *                       Fix zero padding of the last written block in
+ *                        case the tape block size is larger than PAGE_SIZE.
+ *                       Decrease the default disconnection time to tn.
+ * Ver 1.16e Oct  3 99   Minor fixes.
+ * Ver 1.16e1 Oct 13 99  Patches by Arnold Niessen,
+ *                          niessen@iae.nl / arnold.niessen@philips.com
+ *                   GO-1)  Undefined code in idetape_read_position
+ *				according to Gadi's email
+ *                   AJN-1) Minor fix asc == 11 should be asc == 0x11
+ *                               in idetape_issue_packet_command (did effect
+ *                               debugging output only)
+ *                   AJN-2) Added more debugging output, and
+ *                              added ide-tape: where missing. I would also
+ *				like to add tape->name where possible
+ *                   AJN-3) Added different debug_level's 
+ *                              via /proc/ide/hdc/settings
+ * 				"debug_level" determines amount of debugging output;
+ * 				can be changed using /proc/ide/hdx/settings
+ * 				0 : almost no debugging output
+ * 				1 : 0+output errors only
+ * 				2 : 1+output all sensekey/asc
+ * 				3 : 2+follow all chrdev related procedures
+ * 				4 : 3+follow all procedures
+ * 				5 : 4+include pc_stack rq_stack info
+ * 				6 : 5+USE_COUNT updates
+ *                   AJN-4) Fixed timeout for retension in idetape_queue_pc_tail
+ *				from 5 to 10 minutes
+ *                   AJN-5) Changed maximum number of blocks to skip when
+ *                              reading tapes with multiple consecutive write
+ *                              errors from 100 to 1000 in idetape_get_logical_blk
+ *                   Proposed changes to code:
+ *                   1) output "logical_blk_num" via /proc
+ *                   2) output "current_operation" via /proc
+ *                   3) Either solve or document the fact that `mt rewind' is
+ *                      required after reading from /dev/nhtx to be
+ *			able to rmmod the idetape module;
+ *			Also, sometimes an application finishes but the
+ *			device remains `busy' for some time. Same cause ?
+ *                   Proposed changes to release-notes:
+ *		     4) write a simple `quickstart' section in the
+ *                      release notes; I volunteer if you don't want to
+ * 		     5) include a pointer to video4linux in the doc
+ *                      to stimulate video applications
+ *                   6) release notes lines 331 and 362: explain what happens
+ *			if the application data rate is higher than 1100 KB/s; 
+ *			similar approach to lower-than-500 kB/s ?
+ *		     7) 6.6 Comparison; wouldn't it be better to allow different 
+ *			strategies for read and write ?
+ *			Wouldn't it be better to control the tape buffer
+ *			contents instead of the bandwidth ?
+ *		     8) line 536: replace will by would (if I understand
+ *			this section correctly, a hypothetical and unwanted situation
+ *			 is being described)
+ * Ver 1.16f Dec 15 99   Change place of the secondary OnStream header frames.
+ * Ver 1.17  Nov 2000 / Jan 2001  Marcel Mol, marcel@mesa.nl
+ *			- Add idetape_onstream_mode_sense_tape_parameter_page
+ *			  function to get tape capacity in frames: tape->capacity.
+ *			- Add support for DI-50 drives( or any DI- drive).
+ *			- 'workaround' for read error/blank block around block 3000.
+ *			- Implement Early warning for end of media for Onstream.
+ *			- Cosmetic code changes for readability.
+ *			- Idetape_position_tape should not use SKIP bit during
+ *			  Onstream read recovery.
+ *			- Add capacity, logical_blk_num and first/last_frame_position
+ *			  to /proc/ide/hd?/settings.
+ *			- Module use count was gone in the Linux 2.4 driver.
+ * Ver 1.17a Apr 2001 Willem Riede osst@riede.org
+ * 			- Get drive's actual block size from mode sense block descriptor
+ * 			- Limit size of pipeline
+ * Ver 1.17b Oct 2002   Alan Stern <stern@rowland.harvard.edu>
+ *			Changed IDETAPE_MIN_PIPELINE_STAGES to 1 and actually used
+ *			 it in the code!
+ *			Actually removed aborted stages in idetape_abort_pipeline
+ *			 instead of just changing the command code.
+ *			Made the transfer byte count for Request Sense equal to the
+ *			 actual length of the data transfer.
+ *			Changed handling of partial data transfers: they do not
+ *			 cause DMA errors.
+ *			Moved initiation of DMA transfers to the correct place.
+ *			Removed reference to unallocated memory.
+ *			Made __idetape_discard_read_pipeline return the number of
+ *			 sectors skipped, not the number of stages.
+ *			Replaced errant kfree() calls with __idetape_kfree_stage().
+ *			Fixed off-by-one error in testing the pipeline length.
+ *			Fixed handling of filemarks in the read pipeline.
+ *			Small code optimization for MTBSF and MTBSFM ioctls.
+ *			Don't try to unlock the door during device close if is
+ *			 already unlocked!
+ *			Cosmetic fixes to miscellaneous debugging output messages.
+ *			Set the minimum /proc/ide/hd?/settings values for "pipeline",
+ *			 "pipeline_min", and "pipeline_max" to 1.
+ *
+ * Here are some words from the first releases of hd.c, which are quoted
+ * in ide.c and apply here as well:
+ *
+ * | Special care is recommended.  Have Fun!
+ *
+ */
+
+/*
+ * An overview of the pipelined operation mode.
+ *
+ * In the pipelined write mode, we will usually just add requests to our
+ * pipeline and return immediately, before we even start to service them. The
+ * user program will then have enough time to prepare the next request while
+ * we are still busy servicing previous requests. In the pipelined read mode,
+ * the situation is similar - we add read-ahead requests into the pipeline,
+ * before the user even requested them.
+ *
+ * The pipeline can be viewed as a "safety net" which will be activated when
+ * the system load is high and prevents the user backup program from keeping up
+ * with the current tape speed. At this point, the pipeline will get
+ * shorter and shorter but the tape will still be streaming at the same speed.
+ * Assuming we have enough pipeline stages, the system load will hopefully
+ * decrease before the pipeline is completely empty, and the backup program
+ * will be able to "catch up" and refill the pipeline again.
+ * 
+ * When using the pipelined mode, it would be best to disable any type of
+ * buffering done by the user program, as ide-tape already provides all the
+ * benefits in the kernel, where it can be done in a more efficient way.
+ * As we will usually not block the user program on a request, the most
+ * efficient user code will then be a simple read-write-read-... cycle.
+ * Any additional logic will usually just slow down the backup process.
+ *
+ * Using the pipelined mode, I get a constant over 400 KBps throughput,
+ * which seems to be the maximum throughput supported by my tape.
+ *
+ * However, there are some downfalls:
+ *
+ *	1.	We use memory (for data buffers) in proportional to the number
+ *		of pipeline stages (each stage is about 26 KB with my tape).
+ *	2.	In the pipelined write mode, we cheat and postpone error codes
+ *		to the user task. In read mode, the actual tape position
+ *		will be a bit further than the last requested block.
+ *
+ * Concerning (1):
+ *
+ *	1.	We allocate stages dynamically only when we need them. When
+ *		we don't need them, we don't consume additional memory. In
+ *		case we can't allocate stages, we just manage without them
+ *		(at the expense of decreased throughput) so when Linux is
+ *		tight in memory, we will not pose additional difficulties.
+ *
+ *	2.	The maximum number of stages (which is, in fact, the maximum
+ *		amount of memory) which we allocate is limited by the compile
+ *		time parameter IDETAPE_MAX_PIPELINE_STAGES.
+ *
+ *	3.	The maximum number of stages is a controlled parameter - We
+ *		don't start from the user defined maximum number of stages
+ *		but from the lower IDETAPE_MIN_PIPELINE_STAGES (again, we
+ *		will not even allocate this amount of stages if the user
+ *		program can't handle the speed). We then implement a feedback
+ *		loop which checks if the pipeline is empty, and if it is, we
+ *		increase the maximum number of stages as necessary until we
+ *		reach the optimum value which just manages to keep the tape
+ *		busy with minimum allocated memory or until we reach
+ *		IDETAPE_MAX_PIPELINE_STAGES.
+ *
+ * Concerning (2):
+ *
+ *	In pipelined write mode, ide-tape can not return accurate error codes
+ *	to the user program since we usually just add the request to the
+ *      pipeline without waiting for it to be serviced. In case an error
+ *      occurs, I will report it on the next user request.
+ *
+ *	In the pipelined read mode, subsequent read requests or forward
+ *	filemark spacing will perform correctly, as we preserve all blocks
+ *	and filemarks which we encountered during our excess read-ahead.
+ * 
+ *	For accurate tape positioning and error reporting, disabling
+ *	pipelined mode might be the best option.
+ *
+ * You can enable/disable/tune the pipelined operation mode by adjusting
+ * the compile time parameters below.
+ */
+
+/*
+ *	Possible improvements.
+ *
+ *	1.	Support for the ATAPI overlap protocol.
+ *
+ *		In order to maximize bus throughput, we currently use the DSC
+ *		overlap method which enables ide.c to service requests from the
+ *		other device while the tape is busy executing a command. The
+ *		DSC overlap method involves polling the tape's status register
+ *		for the DSC bit, and servicing the other device while the tape
+ *		isn't ready.
+ *
+ *		In the current QIC development standard (December 1995),
+ *		it is recommended that new tape drives will *in addition* 
+ *		implement the ATAPI overlap protocol, which is used for the
+ *		same purpose - efficient use of the IDE bus, but is interrupt
+ *		driven and thus has much less CPU overhead.
+ *
+ *		ATAPI overlap is likely to be supported in most new ATAPI
+ *		devices, including new ATAPI cdroms, and thus provides us
+ *		a method by which we can achieve higher throughput when
+ *		sharing a (fast) ATA-2 disk with any (slow) new ATAPI device.
+ */
+
+#define IDETAPE_VERSION "1.19"
+
+#include <linux/config.h>
+#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>
+#include <linux/major.h>
+#include <linux/devfs_fs_kernel.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>
+
+#include <asm/byteorder.h>
+#include <asm/irq.h>
+#include <asm/uaccess.h>
+#include <asm/io.h>
+#include <asm/unaligned.h>
+
+/*
+ * partition
+ */
+typedef struct os_partition_s {
+	__u8	partition_num;
+	__u8	par_desc_ver;
+	__u16	wrt_pass_cntr;
+	__u32	first_frame_addr;
+	__u32	last_frame_addr;
+	__u32	eod_frame_addr;
+} os_partition_t;
+
+/*
+ * DAT entry
+ */
+typedef struct os_dat_entry_s {
+	__u32	blk_sz;
+	__u16	blk_cnt;
+	__u8	flags;
+	__u8	reserved;
+} os_dat_entry_t;
+
+/*
+ * DAT
+ */
+#define OS_DAT_FLAGS_DATA	(0xc)
+#define OS_DAT_FLAGS_MARK	(0x1)
+
+typedef struct os_dat_s {
+	__u8		dat_sz;
+	__u8		reserved1;
+	__u8		entry_cnt;
+	__u8		reserved3;
+	os_dat_entry_t	dat_list[16];
+} os_dat_t;
+
+#include <linux/mtio.h>
+
+/**************************** 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
+ *	cannot be disabled (calculate_speeds() divides by tape->max_stages.)
+ */
+#define IDETAPE_MIN_PIPELINE_STAGES	  1
+#define IDETAPE_MAX_PIPELINE_STAGES	400
+#define IDETAPE_INCREASE_STAGES_RATE	 20
+
+/*
+ *	The following are used to debug the driver:
+ *
+ *	Setting IDETAPE_DEBUG_INFO to 1 will report device capabilities.
+ *	Setting IDETAPE_DEBUG_LOG to 1 will log driver flow control.
+ *	Setting IDETAPE_DEBUG_BUGS to 1 will enable self-sanity checks in
+ *	some places.
+ *
+ *	Setting them to 0 will restore normal operation mode:
+ *
+ *		1.	Disable logging normal successful operations.
+ *		2.	Disable self-sanity checks.
+ *		3.	Errors will still be logged, of course.
+ *
+ *	All the #if DEBUG code will be removed some day, when the driver
+ *	is verified to be stable enough. This will make it much more
+ *	esthetic.
+ */
+#define IDETAPE_DEBUG_INFO		0
+#define IDETAPE_DEBUG_LOG		0
+#define IDETAPE_DEBUG_BUGS		1
+
+/*
+ *	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
+ *	interactive response, while using a high value might improve sytem
+ *	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 ***********************/
+
+/*
+ *	Debugging/Performance analysis
+ *
+ *	I/O trace support
+ */
+#define USE_IOTRACE	0
+#if USE_IOTRACE
+#include <linux/io_trace.h>
+#define IO_IDETAPE_FIFO	500
+#endif
+
+/*
+ *	Read/Write error simulation
+ */
+#define SIMULATE_ERRORS			0
+
+/*
+ *	For general magnetic tape device compatibility.
+ */
+typedef enum {
+	idetape_direction_none,
+	idetape_direction_read,
+	idetape_direction_write
+} idetape_chrdev_direction_t;
+
+struct idetape_bh {
+	unsigned short b_size;
+	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
+
+/*
+ *	Capabilities and Mechanical Status Page
+ */
+typedef struct {
+	unsigned	page_code	:6;	/* Page code - Should be 0x2a */
+	__u8		reserved0_6	:1;
+	__u8		ps		:1;	/* parameters saveable */
+	__u8		page_length;		/* Page Length - Should be 0x12 */
+	__u8		reserved2, reserved3;
+	unsigned	ro		:1;	/* Read Only Mode */
+	unsigned	reserved4_1234	:4;
+	unsigned	sprev		:1;	/* Supports SPACE in the reverse direction */
+	unsigned	reserved4_67	:2;
+	unsigned	reserved5_012	:3;
+	unsigned	efmt		:1;	/* Supports ERASE command initiated formatting */
+	unsigned	reserved5_4	:1;
+	unsigned	qfa		:1;	/* Supports the QFA two partition formats */
+	unsigned	reserved5_67	:2;
+	unsigned	lock		:1;	/* Supports locking the volume */
+	unsigned	locked		:1;	/* The volume is locked */
+	unsigned	prevent		:1;	/* The device defaults in the prevent state after power up */	
+	unsigned	eject		:1;	/* The device can eject the volume */
+	__u8		disconnect	:1;	/* The device can break request > ctl */	
+	__u8		reserved6_5	:1;
+	unsigned	ecc		:1;	/* Supports error correction */
+	unsigned	cmprs		:1;	/* Supports data compression */
+	unsigned	reserved7_0	:1;
+	unsigned	blk512		:1;	/* Supports 512 bytes block size */
+	unsigned	blk1024		:1;	/* Supports 1024 bytes block size */
+	unsigned	reserved7_3_6	:4;
+	unsigned	blk32768	:1;	/* slowb - the device restricts the byte count for PIO */
+						/* transfers for slow buffer memory ??? */
+						/* Also 32768 block size in some cases */
+	__u16		max_speed;		/* Maximum speed supported in KBps */
+	__u8		reserved10, reserved11;
+	__u16		ctl;			/* Continuous Transfer Limit in blocks */
+	__u16		speed;			/* Current Speed, in KBps */
+	__u16		buffer_size;		/* Buffer Size, in 512 bytes */
+	__u8		reserved18, reserved19;
+} idetape_capabilities_page_t;
+
+/*
+ *	Block Size Page
+ */
+typedef struct {
+	unsigned	page_code	:6;	/* Page code - Should be 0x30 */
+	unsigned	reserved1_6	:1;
+	unsigned	ps		:1;
+	__u8		page_length;		/* Page Length - Should be 2 */
+	__u8		reserved2;
+	unsigned	play32		:1;
+	unsigned	play32_5	:1;
+	unsigned	reserved2_23	:2;
+	unsigned	record32	:1;
+	unsigned	record32_5	:1;
+	unsigned	reserved2_6	:1;
+	unsigned	one		:1;
+} idetape_block_size_page_t;
+
+/*
+ *	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;
+
+/*
+ *	REQUEST SENSE packet command result - Data Format.
+ */
+typedef struct {
+	unsigned	error_code	:7;	/* Current of deferred errors */
+	unsigned	valid		:1;	/* The information field conforms to QIC-157C */
+	__u8		reserved1	:8;	/* Segment Number - Reserved */
+	unsigned	sense_key	:4;	/* Sense Key */
+	unsigned	reserved2_4	:1;	/* Reserved */
+	unsigned	ili		:1;	/* Incorrect Length Indicator */
+	unsigned	eom		:1;	/* End Of Medium */
+	unsigned	filemark 	:1;	/* Filemark */
+	__u32		information __attribute__ ((packed));
+	__u8		asl;			/* Additional sense length (n-7) */
+	__u32		command_specific;	/* Additional command specific information */
+	__u8		asc;			/* Additional Sense Code */
+	__u8		ascq;			/* Additional Sense Code Qualifier */
+	__u8		replaceable_unit_code;	/* Field Replaceable Unit Code */
+	unsigned	sk_specific1 	:7;	/* Sense Key Specific */
+	unsigned	sksv		:1;	/* Sense Key Specific information is valid */
+	__u8		sk_specific2;		/* Sense Key Specific */
+	__u8		sk_specific3;		/* Sense Key Specific */
+	__u8		pad[2];			/* Padding to 20 bytes */
+} idetape_request_sense_result_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 */
+	unsigned long best_dsc_rw_frequency;
+	/* The current polling frequency */
+	unsigned long dsc_polling_frequency;
+	/* Maximum waiting time */
+	unsigned long dsc_timeout;
+
+	/*
+	 *	Read position information
+	 */
+	u8 partition;
+	/* Current block */
+	unsigned int first_frame_position;
+	unsigned int last_frame_position;
+	unsigned int blocks_in_buffer;
+
+	/*
+	 *	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 */
+	idetape_chrdev_direction_t chrdev_direction;
+
+	/*
+	 *	Device information
+	 */
+	/* Usually 512 or 1024 bytes */
+	unsigned short tape_block_size;
+	int user_bs_factor;
+	/* Copy of the tape's Capabilities and Mechanical Page */
+	idetape_capabilities_page_t capabilities;
+
+	/*
+	 *	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.
+	 */
+	/* Pointer