libata: increase 128 KB / cmd limit for ATAPI tape drives
PATCH 1/1 libata: increase 128 KB / cmd limit for ATAPI tape drives
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.
---
drivers/ata/libata-core.c +4 -0
@@ -2126,6 +2126,10 @@ int ata_dev_configure(struct ata_device 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);
include/linux/ata.h +6 -0
@@ -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,
@@ -522,6 +523,11 @@ static inline int atapi_cdb_len(const u1 } } +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) ||
Quoted 8 lines · On Tue, 30 Oct 2007 11:44:35 -0400 Tony Battersby <[email protected]> wrote:
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_sectorsvalue. Themax_sectorsvalue is currently calculated according to the command set for disk drives, which doesn't apply to tape drives. The defaultmax_sectorsvalue of 256 limits ATAPI tape drive commands to 128 KB. This patch against 2.6.24-rc1 increases themax_sectorsvalue for tape drives to 65535, which permits tape drive commands to transfer just under 32 MB.
Seems reasonable to me and is valid for all ATAPI devices as far as I can see since we use READ_10/WRITE_10 commands.
Alan
Jeff Garzik
AppliedQuoted 12 lines · Tony Battersby
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_sectorsvalue. Themax_sectorsvalue is currently calculated according to the command set for disk drives, which doesn't apply to tape drives. The defaultmax_sectorsvalue of 256 limits ATAPI tape drive commands to 128 KB. This patch against 2.6.24-rc1 increases themax_sectorsvalue 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.
Quoted 7 lines
Note that some of the chipset drivers also set their own
max_sectorsvalue, 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 <[email protected]>
applied