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Documentation / ide / ChangeLog.ide-tape.1995-2002




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Based on kernel version 3.13. Page generated on 2014-01-20 22:03 EST.

1	/*
2	 * Ver 0.1   Nov  1 95   Pre-working code :-)
3	 * Ver 0.2   Nov 23 95   A short backup (few megabytes) and restore procedure
4	 *                        was successful ! (Using tar cvf ... on the block
5	 *                        device interface).
6	 *                       A longer backup resulted in major swapping, bad
7	 *                        overall Linux performance and eventually failed as
8	 *                        we received non serial read-ahead requests from the
9	 *                        buffer cache.
10	 * Ver 0.3   Nov 28 95   Long backups are now possible, thanks to the
11	 *                        character device interface. Linux's responsiveness
12	 *                        and performance doesn't seem to be much affected
13	 *                        from the background backup procedure.
14	 *                       Some general mtio.h magnetic tape operations are
15	 *                        now supported by our character device. As a result,
16	 *                        popular tape utilities are starting to work with
17	 *                        ide tapes :-)
18	 *                       The following configurations were tested:
19	 *                       1. An IDE ATAPI TAPE shares the same interface
20	 *                        and irq with an IDE ATAPI CDROM.
21	 *                       2. An IDE ATAPI TAPE shares the same interface
22	 *                        and irq with a normal IDE disk.
23	 *                        Both configurations seemed to work just fine !
24	 *                        However, to be on the safe side, it is meanwhile
25	 *                        recommended to give the IDE TAPE its own interface
26	 *                        and irq.
27	 *                       The one thing which needs to be done here is to
28	 *                        add a "request postpone" feature to ide.c,
29	 *                        so that we won't have to wait for the tape to finish
30	 *                        performing a long media access (DSC) request (such
31	 *                        as a rewind) before we can access the other device
32	 *                        on the same interface. This effect doesn't disturb
33	 *                        normal operation most of the time because read/write
34	 *                        requests are relatively fast, and once we are
35	 *                        performing one tape r/w request, a lot of requests
36	 *                        from the other device can be queued and ide.c will
37	 *			  service all of them after this single tape request.
38	 * Ver 1.0   Dec 11 95   Integrated into Linux 1.3.46 development tree.
39	 *                       On each read / write request, we now ask the drive
40	 *                        if we can transfer a constant number of bytes
41	 *                        (a parameter of the drive) only to its buffers,
42	 *                        without causing actual media access. If we can't,
43	 *                        we just wait until we can by polling the DSC bit.
44	 *                        This ensures that while we are not transferring
45	 *                        more bytes than the constant referred to above, the
46	 *                        interrupt latency will not become too high and
47	 *                        we won't cause an interrupt timeout, as happened
48	 *                        occasionally in the previous version.
49	 *                       While polling for DSC, the current request is
50	 *                        postponed and ide.c is free to handle requests from
51	 *                        the other device. This is handled transparently to
52	 *                        ide.c. The hwgroup locking method which was used
53	 *                        in the previous version was removed.
54	 *                       Use of new general features which are provided by
55	 *                        ide.c for use with atapi devices.
56	 *                        (Programming done by Mark Lord)
57	 *                       Few potential bug fixes (Again, suggested by Mark)
58	 *                       Single character device data transfers are now
59	 *                        not limited in size, as they were before.
60	 *                       We are asking the tape about its recommended
61	 *                        transfer unit and send a larger data transfer
62	 *                        as several transfers of the above size.
63	 *                        For best results, use an integral number of this
64	 *                        basic unit (which is shown during driver
65	 *                        initialization). I will soon add an ioctl to get
66	 *                        this important parameter.
67	 *                       Our data transfer buffer is allocated on startup,
68	 *                        rather than before each data transfer. This should
69	 *                        ensure that we will indeed have a data buffer.
70	 * Ver 1.1   Dec 14 95   Fixed random problems which occurred when the tape
71	 *                        shared an interface with another device.
72	 *                        (poll_for_dsc was a complete mess).
73	 *                       Removed some old (non-active) code which had
74	 *                        to do with supporting buffer cache originated
75	 *                        requests.
76	 *                       The block device interface can now be opened, so
77	 *                        that general ide driver features like the unmask
78	 *                        interrupts flag can be selected with an ioctl.
79	 *                        This is the only use of the block device interface.
80	 *                       New fast pipelined operation mode (currently only on
81	 *                        writes). When using the pipelined mode, the
82	 *                        throughput can potentially reach the maximum
83	 *                        tape supported throughput, regardless of the
84	 *                        user backup program. On my tape drive, it sometimes
85	 *                        boosted performance by a factor of 2. Pipelined
86	 *                        mode is enabled by default, but since it has a few
87	 *                        downfalls as well, you may want to disable it.
88	 *                        A short explanation of the pipelined operation mode
89	 *                        is available below.
90	 * Ver 1.2   Jan  1 96   Eliminated pipelined mode race condition.
91	 *                       Added pipeline read mode. As a result, restores
92	 *                        are now as fast as backups.
93	 *                       Optimized shared interface behavior. The new behavior
94	 *                        typically results in better IDE bus efficiency and
95	 *                        higher tape throughput.
96	 *                       Pre-calculation of the expected read/write request
97	 *                        service time, based on the tape's parameters. In
98	 *                        the pipelined operation mode, this allows us to
99	 *                        adjust our polling frequency to a much lower value,
100	 *                        and thus to dramatically reduce our load on Linux,
101	 *                        without any decrease in performance.
102	 *                       Implemented additional mtio.h operations.
103	 *                       The recommended user block size is returned by
104	 *                        the MTIOCGET ioctl.
105	 *                       Additional minor changes.
106	 * Ver 1.3   Feb  9 96   Fixed pipelined read mode bug which prevented the
107	 *                        use of some block sizes during a restore procedure.
108	 *                       The character device interface will now present a
109	 *                        continuous view of the media - any mix of block sizes
110	 *                        during a backup/restore procedure is supported. The
111	 *                        driver will buffer the requests internally and
112	 *                        convert them to the tape's recommended transfer
113	 *                        unit, making performance almost independent of the
114	 *                        chosen user block size.
115	 *                       Some improvements in error recovery.
116	 *                       By cooperating with ide-dma.c, bus mastering DMA can
117	 *                        now sometimes be used with IDE tape drives as well.
118	 *                        Bus mastering DMA has the potential to dramatically
119	 *                        reduce the CPU's overhead when accessing the device,
120	 *                        and can be enabled by using hdparm -d1 on the tape's
121	 *                        block device interface. For more info, read the
122	 *                        comments in ide-dma.c.
123	 * Ver 1.4   Mar 13 96   Fixed serialize support.
124	 * Ver 1.5   Apr 12 96   Fixed shared interface operation, broken in 1.3.85.
125	 *                       Fixed pipelined read mode inefficiency.
126	 *                       Fixed nasty null dereferencing bug.
127	 * Ver 1.6   Aug 16 96   Fixed FPU usage in the driver.
128	 *                       Fixed end of media bug.
129	 * Ver 1.7   Sep 10 96   Minor changes for the CONNER CTT8000-A model.
130	 * Ver 1.8   Sep 26 96   Attempt to find a better balance between good
131	 *                        interactive response and high system throughput.
132	 * Ver 1.9   Nov  5 96   Automatically cross encountered filemarks rather
133	 *                        than requiring an explicit FSF command.
134	 *                       Abort pending requests at end of media.
135	 *                       MTTELL was sometimes returning incorrect results.
136	 *                       Return the real block size in the MTIOCGET ioctl.
137	 *                       Some error recovery bug fixes.
138	 * Ver 1.10  Nov  5 96   Major reorganization.
139	 *                       Reduced CPU overhead a bit by eliminating internal
140	 *                        bounce buffers.
141	 *                       Added module support.
142	 *                       Added multiple tape drives support.
143	 *                       Added partition support.
144	 *                       Rewrote DSC handling.
145	 *                       Some portability fixes.
146	 *                       Removed ide-tape.h.
147	 *                       Additional minor changes.
148	 * Ver 1.11  Dec  2 96   Bug fix in previous DSC timeout handling.
149	 *                       Use ide_stall_queue() for DSC overlap.
150	 *                       Use the maximum speed rather than the current speed
151	 *                        to compute the request service time.
152	 * Ver 1.12  Dec  7 97   Fix random memory overwriting and/or last block data
153	 *                        corruption, which could occur if the total number
154	 *                        of bytes written to the tape was not an integral
155	 *                        number of tape blocks.
156	 *                       Add support for INTERRUPT DRQ devices.
157	 * Ver 1.13  Jan  2 98   Add "speed == 0" work-around for HP COLORADO 5GB
158	 * Ver 1.14  Dec 30 98   Partial fixes for the Sony/AIWA tape drives.
159	 *                       Replace cli()/sti() with hwgroup spinlocks.
160	 * Ver 1.15  Mar 25 99   Fix SMP race condition by replacing hwgroup
161	 *                        spinlock with private per-tape spinlock.
162	 * Ver 1.16  Sep  1 99   Add OnStream tape support.
163	 *                       Abort read pipeline on EOD.
164	 *                       Wait for the tape to become ready in case it returns
165	 *                        "in the process of becoming ready" on open().
166	 *                       Fix zero padding of the last written block in
167	 *                        case the tape block size is larger than PAGE_SIZE.
168	 *                       Decrease the default disconnection time to tn.
169	 * Ver 1.16e Oct  3 99   Minor fixes.
170	 * Ver 1.16e1 Oct 13 99  Patches by Arnold Niessen,
171	 *                          niessen@iae.nl / arnold.niessen@philips.com
172	 *                   GO-1)  Undefined code in idetape_read_position
173	 *				according to Gadi's email
174	 *                   AJN-1) Minor fix asc == 11 should be asc == 0x11
175	 *                               in idetape_issue_packet_command (did effect
176	 *                               debugging output only)
177	 *                   AJN-2) Added more debugging output, and
178	 *                              added ide-tape: where missing. I would also
179	 *				like to add tape->name where possible
180	 *                   AJN-3) Added different debug_level's
181	 *                              via /proc/ide/hdc/settings
182	 *				"debug_level" determines amount of debugging output;
183	 *				can be changed using /proc/ide/hdx/settings
184	 *				0 : almost no debugging output
185	 *				1 : 0+output errors only
186	 *				2 : 1+output all sensekey/asc
187	 *				3 : 2+follow all chrdev related procedures
188	 *				4 : 3+follow all procedures
189	 *				5 : 4+include pc_stack rq_stack info
190	 *				6 : 5+USE_COUNT updates
191	 *                   AJN-4) Fixed timeout for retension in idetape_queue_pc_tail
192	 *				from 5 to 10 minutes
193	 *                   AJN-5) Changed maximum number of blocks to skip when
194	 *                              reading tapes with multiple consecutive write
195	 *                              errors from 100 to 1000 in idetape_get_logical_blk
196	 *                   Proposed changes to code:
197	 *                   1) output "logical_blk_num" via /proc
198	 *                   2) output "current_operation" via /proc
199	 *                   3) Either solve or document the fact that `mt rewind' is
200	 *                      required after reading from /dev/nhtx to be
201	 *			able to rmmod the idetape module;
202	 *			Also, sometimes an application finishes but the
203	 *			device remains `busy' for some time. Same cause ?
204	 *                   Proposed changes to release-notes:
205	 *		     4) write a simple `quickstart' section in the
206	 *                      release notes; I volunteer if you don't want to
207	 *		     5) include a pointer to video4linux in the doc
208	 *                      to stimulate video applications
209	 *                   6) release notes lines 331 and 362: explain what happens
210	 *			if the application data rate is higher than 1100 KB/s;
211	 *			similar approach to lower-than-500 kB/s ?
212	 *		     7) 6.6 Comparison; wouldn't it be better to allow different
213	 *			strategies for read and write ?
214	 *			Wouldn't it be better to control the tape buffer
215	 *			contents instead of the bandwidth ?
216	 *		     8) line 536: replace will by would (if I understand
217	 *			this section correctly, a hypothetical and unwanted situation
218	 *			 is being described)
219	 * Ver 1.16f Dec 15 99   Change place of the secondary OnStream header frames.
220	 * Ver 1.17  Nov 2000 / Jan 2001  Marcel Mol, marcel@mesa.nl
221	 *			- Add idetape_onstream_mode_sense_tape_parameter_page
222	 *			  function to get tape capacity in frames: tape->capacity.
223	 *			- Add support for DI-50 drives( or any DI- drive).
224	 *			- 'workaround' for read error/blank block around block 3000.
225	 *			- Implement Early warning for end of media for Onstream.
226	 *			- Cosmetic code changes for readability.
227	 *			- Idetape_position_tape should not use SKIP bit during
228	 *			  Onstream read recovery.
229	 *			- Add capacity, logical_blk_num and first/last_frame_position
230	 *			  to /proc/ide/hd?/settings.
231	 *			- Module use count was gone in the Linux 2.4 driver.
232	 * Ver 1.17a Apr 2001 Willem Riede osst@riede.org
233	 *			- Get drive's actual block size from mode sense block descriptor
234	 *			- Limit size of pipeline
235	 * Ver 1.17b Oct 2002   Alan Stern <stern@rowland.harvard.edu>
236	 *			Changed IDETAPE_MIN_PIPELINE_STAGES to 1 and actually used
237	 *			 it in the code!
238	 *			Actually removed aborted stages in idetape_abort_pipeline
239	 *			 instead of just changing the command code.
240	 *			Made the transfer byte count for Request Sense equal to the
241	 *			 actual length of the data transfer.
242	 *			Changed handling of partial data transfers: they do not
243	 *			 cause DMA errors.
244	 *			Moved initiation of DMA transfers to the correct place.
245	 *			Removed reference to unallocated memory.
246	 *			Made __idetape_discard_read_pipeline return the number of
247	 *			 sectors skipped, not the number of stages.
248	 *			Replaced errant kfree() calls with __idetape_kfree_stage().
249	 *			Fixed off-by-one error in testing the pipeline length.
250	 *			Fixed handling of filemarks in the read pipeline.
251	 *			Small code optimization for MTBSF and MTBSFM ioctls.
252	 *			Don't try to unlock the door during device close if is
253	 *			 already unlocked!
254	 *			Cosmetic fixes to miscellaneous debugging output messages.
255	 *			Set the minimum /proc/ide/hd?/settings values for "pipeline",
256	 *			 "pipeline_min", and "pipeline_max" to 1.
257	 */
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