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Commit 9e47be0c authored by Bartlomiej Zolnierkiewicz's avatar Bartlomiej Zolnierkiewicz
Browse files

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: default avatarSergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: default avatarBartlomiej Zolnierkiewicz <bzolnier@gmail.com>
parent 3a5015cc

Documentation/ide.txt

+0 −4
Original line number Diff line number Diff line
@@ -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.

drivers/ide/ide-disk.c

+0 −1
Original line number Diff line number Diff line
@@ -761,7 +761,6 @@ static void idedisk_add_settings(ide_drive_t *drive) 
	ide_add_setting(drive,	"bios_head",	SETTING_RW,	TYPE_BYTE,	0,	255,			1,	1,	&drive->bios_head,	NULL);

	ide_add_setting(drive,	"bios_sect",	SETTING_RW,	TYPE_BYTE,	0,	63,			1,	1,	&drive->bios_sect,	NULL);

	ide_add_setting(drive,	"address",	SETTING_RW,	TYPE_BYTE,	0,	2,			1,	1,	&drive->addressing,	set_lba_addressing);

	ide_add_setting(drive,	"bswap",	SETTING_READ,	TYPE_BYTE,	0,	1,			1,	1,	&drive->bswap,		NULL);

	ide_add_setting(drive,	"multcount",	SETTING_RW,	TYPE_BYTE,	0,	id->max_multsect,	1,	1,	&drive->mult_count,	set_multcount);

	ide_add_setting(drive,	"nowerr",	SETTING_RW,	TYPE_BYTE,	0,	1,			1,	1,	&drive->nowerr,		set_nowerr);

	ide_add_setting(drive,	"lun",		SETTING_RW,	TYPE_INT,	0,	7,			1,	1,	&drive->lun,		NULL);

drivers/ide/ide-taskfile.c

+2 −30
Original line number Diff line number Diff line
@@ -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

drivers/ide/ide.c

+1 −5
Original line number Diff line number Diff line
@@ -1303,7 +1303,7 @@ static int __init ide_setup(char *s) 
	if (s[0] == 'h' && s[1] == 'd' && s[2] >= 'a' && s[2] <= max_drive) {

		const char *hd_words[] = {

			"none", "noprobe", "nowerr", "cdrom", "nodma",

			"autotune", "noautotune", "minus8", "swapdata", "bswap",

			"autotune", "noautotune", "-8", "-9", "-10",

			"noflush", "remap", "remap63", "scsi", NULL };

		unit = s[2] - 'a';

		hw   = unit / MAX_DRIVES;
@@ -1339,10 +1339,6 @@ static int __init ide_setup(char *s) 
			case -7: /* "noautotune" */

				drive->autotune = IDE_TUNE_NOAUTO;

				goto obsolete_option;

			case -9: /* "swapdata" */

			case -10: /* "bswap" */

				drive->bswap = 1;

				goto done;

			case -11: /* noflush */

				drive->noflush = 1;

				goto done;

include/linux/ide.h

+0 −1
Original line number Diff line number Diff line
@@ -394,7 +394,6 @@ typedef struct ide_drive_s { 
	u8	state;			/* retry state */

	u8	waiting_for_dma;	/* dma currently in progress */

	u8	unmask;			/* okay to unmask other irqs */

	u8	bswap;			/* byte swap data */

	u8	noflush;		/* don't attempt flushes */

	u8	dsc_overlap;		/* DSC overlap */

	u8	nice1;			/* give potential excess bandwidth */