linux/drivers/scsi/sd.h
Alan Jenkins 2b14290078 [SCSI] extend the last_sector_bug flag to cover more sectors
The last_sector_bug flag was added to work around a bug in certain usb
cardreaders, where they would crash if a multiple sector read included the
last sector. The original implementation avoids this by e.g. splitting an 8
sector read which includes the last sector into a 7 sector read, and a single
sector read for the last sector.  The flag is enabled for all USB devices.

This revealed a second bug in other usb cardreaders, which crash when they
get a multiple sector read which stops 1 sector short of the last sector.
Affected hardware includes the Kingston "MobileLite" external USB cardreader
and the internal USB cardreader on the Asus EeePC.

Extend the last_sector_bug workaround to ensure that any access which touches
the last 8 hardware sectors of the device is a single sector long.  Requests
are shrunk as necessary to meet this constraint.

This gives us a safety margin against potential unknown or future bugs
affecting multi-sector access to the end of the device.  The two known bugs
only affect the last 2 sectors.  However, they suggest that these devices
are prone to fencepost errors and that multi-sector access to the end of the
device is not well tested.  Popular OS's use multi-sector accesses, but they
rarely read the last few sectors.  Linux (with udev & vol_id) automatically
reads sectors from the end of the device on insertion.  It is assumed that
single sector accesses are more thoroughly tested during development.

Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
Tested-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
2008-07-27 10:16:13 -04:00

117 lines
3.2 KiB
C

#ifndef _SCSI_DISK_H
#define _SCSI_DISK_H
/*
* More than enough for everybody ;) The huge number of majors
* is a leftover from 16bit dev_t days, we don't really need that
* much numberspace.
*/
#define SD_MAJORS 16
/*
* This is limited by the naming scheme enforced in sd_probe,
* add another character to it if you really need more disks.
*/
#define SD_MAX_DISKS (((26 * 26) + 26 + 1) * 26)
/*
* Time out in seconds for disks and Magneto-opticals (which are slower).
*/
#define SD_TIMEOUT (30 * HZ)
#define SD_MOD_TIMEOUT (75 * HZ)
/*
* Number of allowed retries
*/
#define SD_MAX_RETRIES 5
#define SD_PASSTHROUGH_RETRIES 1
/*
* Size of the initial data buffer for mode and read capacity data
*/
#define SD_BUF_SIZE 512
/*
* Number of sectors at the end of the device to avoid multi-sector
* accesses to in the case of last_sector_bug
*/
#define SD_LAST_BUGGY_SECTORS 8
struct scsi_disk {
struct scsi_driver *driver; /* always &sd_template */
struct scsi_device *device;
struct device dev;
struct gendisk *disk;
unsigned int openers; /* protected by BKL for now, yuck */
sector_t capacity; /* size in 512-byte sectors */
u32 index;
u8 media_present;
u8 write_prot;
u8 protection_type;/* Data Integrity Field */
unsigned previous_state : 1;
unsigned ATO : 1; /* state of disk ATO bit */
unsigned WCE : 1; /* state of disk WCE bit */
unsigned RCD : 1; /* state of disk RCD bit, unused */
unsigned DPOFUA : 1; /* state of disk DPOFUA bit */
};
#define to_scsi_disk(obj) container_of(obj,struct scsi_disk,dev)
static inline struct scsi_disk *scsi_disk(struct gendisk *disk)
{
return container_of(disk->private_data, struct scsi_disk, driver);
}
#define sd_printk(prefix, sdsk, fmt, a...) \
(sdsk)->disk ? \
sdev_printk(prefix, (sdsk)->device, "[%s] " fmt, \
(sdsk)->disk->disk_name, ##a) : \
sdev_printk(prefix, (sdsk)->device, fmt, ##a)
/*
* A DIF-capable target device can be formatted with different
* protection schemes. Currently 0 through 3 are defined:
*
* Type 0 is regular (unprotected) I/O
*
* Type 1 defines the contents of the guard and reference tags
*
* Type 2 defines the contents of the guard and reference tags and
* uses 32-byte commands to seed the latter
*
* Type 3 defines the contents of the guard tag only
*/
enum sd_dif_target_protection_types {
SD_DIF_TYPE0_PROTECTION = 0x0,
SD_DIF_TYPE1_PROTECTION = 0x1,
SD_DIF_TYPE2_PROTECTION = 0x2,
SD_DIF_TYPE3_PROTECTION = 0x3,
};
/*
* Data Integrity Field tuple.
*/
struct sd_dif_tuple {
__be16 guard_tag; /* Checksum */
__be16 app_tag; /* Opaque storage */
__be32 ref_tag; /* Target LBA or indirect LBA */
};
#if defined(CONFIG_BLK_DEV_INTEGRITY)
extern void sd_dif_op(struct scsi_cmnd *, unsigned int, unsigned int);
extern void sd_dif_config_host(struct scsi_disk *);
extern int sd_dif_prepare(struct request *rq, sector_t, unsigned int);
extern void sd_dif_complete(struct scsi_cmnd *, unsigned int);
#else /* CONFIG_BLK_DEV_INTEGRITY */
#define sd_dif_op(a, b, c) do { } while (0)
#define sd_dif_config_host(a) do { } while (0)
#define sd_dif_prepare(a, b, c) (0)
#define sd_dif_complete(a, b) (0)
#endif /* CONFIG_BLK_DEV_INTEGRITY */
#endif /* _SCSI_DISK_H */