X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=Documentation%2Ffilesystems%2Fudf.txt;h=fde829a756e6510a9d5cd4d56c981e204151fa8c;hb=a2f44b27303a5353859d77a3e96a1d3f33f56ab7;hp=e5213bc301f721a1c3236a4469194982c9653865;hpb=134734d875a0a48d994ef20b9905209b4b8b6f75;p=linux-2.6.git

diff --git a/Documentation/filesystems/udf.txt b/Documentation/filesystems/udf.txt
index e5213bc30..fde829a75 100644
--- a/Documentation/filesystems/udf.txt
+++ b/Documentation/filesystems/udf.txt
@@ -7,8 +7,17 @@ If you encounter problems with reading UDF discs using this driver,
 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:
@@ -26,6 +35,20 @@ The following mount options are supported:
 	nostrict	Unset strict conformance
 	iocharset=	Set the NLS character set
 
+The uid= and gid= options need a bit more explaining.  They will accept a
+decimal numeric value which will be used as the default ID for that mount.
+They will also accept the string "ignore" and "forget".  For files on the disk
+that are owned by nobody ( -1 ), they will instead look as if they are owned
+by the default ID.  The ignore option causes the default ID to override all
+IDs on the disk, not just -1.  The forget option causes all IDs to be written
+to disk as -1, so when the media is later remounted, they will appear to be
+owned by whatever default ID it is mounted with at that time.
+
+For typical desktop use of removable media, you should set the ID to that
+of the interactively logged on user, and also specify both the forget and
+ignore options.  This way the interactive user will always see the files
+on the disk as belonging to him.
+
 The remaining are for debugging and disaster recovery:
 
 	novrs		Skip volume sequence recognition