1==============
2Packet writing
3==============
4
5Getting started quick
6---------------------
7
8- Select packet support in the block device section and UDF support in
9  the file system section.
10
11- Compile and install kernel and modules, reboot.
12
13- You need the udftools package (pktsetup, mkudffs, cdrwtool).
14  Download from https://github.com/pali/udftools
15
16- Grab a new CD-RW disc and format it (assuming CD-RW is hdc, substitute
17  as appropriate)::
18
19	# cdrwtool -d /dev/hdc -q
20
21- Setup your writer::
22
23	# pktsetup dev_name /dev/hdc
24
25- Now you can mount /dev/pktcdvd/dev_name and copy files to it. Enjoy::
26
27	# mount /dev/pktcdvd/dev_name /cdrom -t udf -o rw,noatime
28
29
30Packet writing for DVD-RW media
31-------------------------------
32
33DVD-RW discs can be written to much like CD-RW discs if they are in
34the so called "restricted overwrite" mode. To put a disc in restricted
35overwrite mode, run::
36
37	# dvd+rw-format /dev/hdc
38
39You can then use the disc the same way you would use a CD-RW disc::
40
41	# pktsetup dev_name /dev/hdc
42	# mount /dev/pktcdvd/dev_name /cdrom -t udf -o rw,noatime
43
44
45Packet writing for DVD+RW media
46-------------------------------
47
48According to the DVD+RW specification, a drive supporting DVD+RW discs
49shall implement "true random writes with 2KB granularity", which means
50that it should be possible to put any filesystem with a block size >=
512KB on such a disc. For example, it should be possible to do::
52
53	# dvd+rw-format /dev/hdc   (only needed if the disc has never
54	                            been formatted)
55	# mkudffs /dev/hdc
56	# mount /dev/hdc /cdrom -t udf -o rw,noatime
57
58However, some drives don't follow the specification and expect the
59host to perform aligned writes at 32KB boundaries. Other drives do
60follow the specification, but suffer bad performance problems if the
61writes are not 32KB aligned.
62
63Both problems can be solved by using the pktcdvd driver, which always
64generates aligned writes::
65
66	# dvd+rw-format /dev/hdc
67	# pktsetup dev_name /dev/hdc
68	# mkudffs /dev/pktcdvd/dev_name
69	# mount /dev/pktcdvd/dev_name /cdrom -t udf -o rw,noatime
70
71
72Packet writing for DVD-RAM media
73--------------------------------
74
75DVD-RAM discs are random writable, so using the pktcdvd driver is not
76necessary. However, using the pktcdvd driver can improve performance
77in the same way it does for DVD+RW media.
78
79
80Notes
81-----
82
83- CD-RW media can usually not be overwritten more than about 1000
84  times, so to avoid unnecessary wear on the media, you should always
85  use the noatime mount option.
86
87- Defect management (ie automatic remapping of bad sectors) has not
88  been implemented yet, so you are likely to get at least some
89  filesystem corruption if the disc wears out.
90
91- Since the pktcdvd driver makes the disc appear as a regular block
92  device with a 2KB block size, you can put any filesystem you like on
93  the disc. For example, run::
94
95	# /sbin/mke2fs /dev/pktcdvd/dev_name
96
97  to create an ext2 filesystem on the disc.
98
99
100Using the pktcdvd sysfs interface
101---------------------------------
102
103Since Linux 2.6.20, the pktcdvd module has a sysfs interface
104and can be controlled by it. For example the "pktcdvd" tool uses
105this interface. (see http://tom.ist-im-web.de/linux/software/pktcdvd )
106
107"pktcdvd" works similar to "pktsetup", e.g.::
108
109	# pktcdvd -a dev_name /dev/hdc
110	# mkudffs /dev/pktcdvd/dev_name
111	# mount -t udf -o rw,noatime /dev/pktcdvd/dev_name /dvdram
112	# cp files /dvdram
113	# umount /dvdram
114	# pktcdvd -r dev_name
115
116
117For a description of the sysfs interface look into the file:
118
119  Documentation/ABI/testing/sysfs-class-pktcdvd
120
121
122Using the pktcdvd debugfs interface
123-----------------------------------
124
125To read pktcdvd device infos in human readable form, do::
126
127	# cat /sys/kernel/debug/pktcdvd/pktcdvd[0-7]/info
128
129For a description of the debugfs interface look into the file:
130
131  Documentation/ABI/testing/debugfs-pktcdvd
132
133
134
135Links
136-----
137
138See http://fy.chalmers.se/~appro/linux/DVD+RW/ for more information
139about DVD writing.
140