lk/linux-kernel-test
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

ide: remove broken disk byte-swapping support

Browse Source 
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>
This commit is contained in:
Bartlomiej Zolnierkiewicz
2008-01-26 20:13:09 +01:00
parent 3a5015cc9d
commit 9e47be0c97
5 changed files with 3 additions and 41 deletions
Download Patch File Download Diff File Expand all files Collapse all files

32
drivers/ide/ide-taskfile.c
View File

@@ -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