ide: remove broken disk byte-swapping support

Remove broken disk byte-swapping support:
- it can cause a data corruption on SMP (or if using PREEMPT on UP)
- all data coming from disk are byte-swapped by taskfile_*_data() which
  results in incorrect identify data being reported by /proc/ide/ and IOCTLs
- "hdx=bswap/byteswap" kernel parameter has been broken on m68k host drivers
  (including Atari/Q40 ones) since 2.5.x days (because of 'hwif' zero-ing)
- byte-swapping is limited to PIO transfers (for working with TiVo disks on
  x86 machines using user-space solutions or dm-byteswap should result in
  much better performance because DMA can be used)

For previous discussions please see:

http://www.ussg.iu.edu/hypermail/linux/kernel/0201.0/0768.html
http://lkml.org/lkml/2004/2/28/111

[ I have dm-byteswap device mapper target if somebody is interested
  (patch is for 2.6.4 though but I'll dust it off if needed). ]

Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

1 files changed, 0 insertions, 4 deletions

diff --git a/Documentation/ide.txt b/Documentation/ide.txt
index b29ccb43d6cc..94e2e3b9e77f 100644
--- a/Documentation/ide.txt
+++ b/Documentation/ide.txt
@@ -244,10 +244,6 @@ Summary of ide driver parameters for kernel command line
 
  "hdx=nodma"		: disallow DMA
 
- "hdx=swapdata"		: when the drive is a disk, byte swap all data
-
- "hdx=bswap"		: same as above..........
-
  "hdx=scsi"		: the return of the ide-scsi flag, this is useful for
  			  allowing ide-floppy, ide-tape, and ide-cdrom|writers
  			  to use ide-scsi emulation on a device specific option.