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libata: increase 128 KB / cmd limit for ATAPI tape drives

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Commands sent to ATAPI tape drives via the SCSI generic (sg) driver are
limited in the amount of data that they can transfer by the max_sectors
value.  The max_sectors value is currently calculated according to the
command set for disk drives, which doesn't apply to tape drives.  The
default max_sectors value of 256 limits ATAPI tape drive commands to
128 KB.  This patch against 2.6.24-rc1 increases the max_sectors value
for tape drives to 65535, which permits tape drive commands to transfer
just under 32 MB.

Tested with a SuperMicro PDSME motherboard, AHCI, and a Sony SDX-570V
SATA tape drive.

Note that some of the chipset drivers also set their own max_sectors
value, which may override the value set in libata-core.  I don't have
any of these chipsets to test, so I didn't go messing with them.  Also,
ATAPI devices other than tape drives may benefit from similar changes,
but I have only tape drives and disk drives to test.

Signed-off-by: Tony Battersby <tonyb@cybernetics.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
This commit is contained in:
Tony Battersby 2007-10-30 11:44:35 -04:00 committed by Jeff Garzik
parent 03116d67e0
commit f8d8e5799b
2 changed files with 10 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

4
drivers/ata/libata-core.c
View file

@ -2304,6 +2304,10 @@ int ata_dev_configure(struct ata_device *dev)
dev->max_sectors = ATA_MAX_SECTORS;
}
if ((dev->class == ATA_DEV_ATAPI) &&
(atapi_command_packet_set(id) == TYPE_TAPE))
dev->max_sectors = ATA_MAX_SECTORS_TAPE;
if (dev->horkage & ATA_HORKAGE_MAX_SEC_128)
dev->max_sectors = min_t(unsigned int, ATA_MAX_SECTORS_128,
dev->max_sectors);

6
include/linux/ata.h
View file

@ -43,6 +43,7 @@ enum {
ATA_MAX_SECTORS_128 = 128,
ATA_MAX_SECTORS = 256,
ATA_MAX_SECTORS_LBA48 = 65535,/* TODO: 65536? */
ATA_MAX_SECTORS_TAPE = 65535,
ATA_ID_WORDS = 256,
ATA_ID_SERNO = 10,
@ -544,6 +545,11 @@ static inline int atapi_cdb_len(const u16 *dev_id)
}
}
static inline int atapi_command_packet_set(const u16 *dev_id)
{
return (dev_id[0] >> 8) & 0x1f;
}
static inline int is_atapi_taskfile(const struct ata_taskfile *tf)
{
return (tf->protocol == ATA_PROT_ATAPI) ||