[PATCH] Update udf documentation to reflect current state of read/write support

Change Documentation/filesystems/udf.txt from saying that read/write mounts on cd media are not supported to instead state the current level of support. Specifically that it works fine on dvd+rw media and can be made to work on cd-rw media via the pktcdvd device. Cc: Peter Osterlund <petero2@telia.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] Update udf documentation to reflect current state of read/write support
Change Documentation/filesystems/udf.txt from saying that read/write mounts on cd media are not supported to instead state the current level of support. Specifically that it works fine on dvd+rw media and can be made to work on cd-rw media via the pktcdvd device. Cc: Peter Osterlund <petero2@telia.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Phillip Susi · Linus Torvalds
1 parent d6ddf55440
Showing 1 changed file with 11 additions and 2 deletions Side-by-side Diff
Documentation/filesystems/udf.txt
@@ -7,8 +7,17 @@
 please report them to linux_udf@hpesjro.fc.hp.com, which is the
 developer's list.
  
-Write support requires a block driver which supports writing. The current
-scsi and ide cdrom drivers do not support writing.
+Write support requires a block driver which supports writing.  Currently
+dvd+rw drives and media support true random sector writes, and so a udf
+filesystem on such devices can be directly mounted read/write.  CD-RW
+media however, does not support this.  Instead the media can be formatted
+for packet mode using the utility cdrwtool, then the pktcdvd driver can
+be bound to the underlying cd device to provide the required buffering
+and read-modify-write cycles to allow the filesystem random sector writes
+while providing the hardware with only full packet writes.  While not
+required for dvd+rw media, use of the pktcdvd driver often enhances
+performance due to very poor read-modify-write support supplied internally
+by drive firmware.
  
 -------------------------------------------------------------------------------
 The following mount options are supported:
...	...	@@ -7,8 +7,17 @@
7	7	please report them to linux_udf@hpesjro.fc.hp.com, which is the
8	8	developer's list.
9	9
10		-Write support requires a block driver which supports writing. The current
11		-scsi and ide cdrom drivers do not support writing.
	10	+Write support requires a block driver which supports writing. Currently
	11	+dvd+rw drives and media support true random sector writes, and so a udf
	12	+filesystem on such devices can be directly mounted read/write. CD-RW
	13	+media however, does not support this. Instead the media can be formatted
	14	+for packet mode using the utility cdrwtool, then the pktcdvd driver can
	15	+be bound to the underlying cd device to provide the required buffering
	16	+and read-modify-write cycles to allow the filesystem random sector writes
	17	+while providing the hardware with only full packet writes. While not
	18	+required for dvd+rw media, use of the pktcdvd driver often enhances
	19	+performance due to very poor read-modify-write support supplied internally
	20	+by drive firmware.
12	21
13	22	-------------------------------------------------------------------------------
14	23	The following mount options are supported: