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, 2 insertions, 30 deletions

diff --git a/drivers/ide/ide-taskfile.c b/drivers/ide/ide-taskfile.c
index c58edc86ed3..3ecafab8f54 100644
--- a/drivers/ide/ide-taskfile.c
+++ b/drivers/ide/ide-taskfile.c
@@ -35,34 +35,6 @@
 #include <asm/uaccess.h>
 #include <asm/io.h>
 
-static void ata_bswap_data (void *buffer, int wcount)
-{
-	u16 *p = buffer;
-
-	while (wcount--) {
-		*p = *p << 8 | *p >> 8; p++;
-		*p = *p << 8 | *p >> 8; p++;
-	}
-}
-
-static void taskfile_input_data(ide_drive_t *drive, void *buffer, u32 wcount)
-{
-	HWIF(drive)->ata_input_data(drive, buffer, wcount);
-	if (drive->bswap)
-		ata_bswap_data(buffer, wcount);
-}
-
-static void taskfile_output_data(ide_drive_t *drive, void *buffer, u32 wcount)
-{
-	if (drive->bswap) {
-		ata_bswap_data(buffer, wcount);
-		HWIF(drive)->ata_output_data(drive, buffer, wcount);
-		ata_bswap_data(buffer, wcount);
-	} else {
-		HWIF(drive)->ata_output_data(drive, buffer, wcount);
-	}
-}
-
 void ide_tf_load(ide_drive_t *drive, ide_task_t *task)
 {
 	ide_hwif_t *hwif = drive->hwif;
@@ -352,9 +324,9 @@ static void ide_pio_sector(ide_drive_t *drive, unsigned int write)
 
 	/* do the actual data transfer */
 	if (write)
-		taskfile_output_data(drive, buf, SECTOR_WORDS);
+		hwif->ata_output_data(drive, buf, SECTOR_WORDS);
 	else
-		taskfile_input_data(drive, buf, SECTOR_WORDS);
+		hwif->ata_input_data(drive, buf, SECTOR_WORDS);
 
 	kunmap_atomic(buf, KM_BIO_SRC_IRQ);
 #ifdef CONFIG_HIGHMEM