Pull button into test branch

[linux-drm-fsl-dcu.git] / Documentation / filesystems / udf.txt

diff --git a/Documentation/filesystems/udf.txt b/Documentation/filesystems/udf.txt
index 511b4230c0536add9d0650cbc1f702becc2e54e2..fde829a756e6510a9d5cd4d56c981e204151fa8c 100644 (file)
--- 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: