From f8d8e5799b75cf7ad530d2bf2a42229bf7360526 Mon Sep 17 00:00:00 2001 From: Tony Battersby Date: Tue, 30 Oct 2007 11:44:35 -0400 Subject: [PATCH] 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. Signed-off-by: Tony Battersby Signed-off-by: Jeff Garzik --- drivers/ata/libata-core.c | 4 ++++ include/linux/ata.h | 6 ++++++ 2 files changed, 10 insertions(+) diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c index 4dc6befa5760..24b3bd63621f 100644 --- a/drivers/ata/libata-core.c +++ b/drivers/ata/libata-core.c @@ -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); diff --git a/include/linux/ata.h b/include/linux/ata.h index 128dc7ad4901..61535e72834d 100644 --- a/include/linux/ata.h +++ b/include/linux/ata.h @@ -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) ||