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Block driver using virtio.

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The block driver uses scatter-gather lists with sg[0] being the
request information (struct virtio_blk_outhdr) with the type, sector
and inbuf id.  The next N sg entries are the bio itself, then the last
sg is the status byte.  Whether the N entries are in or out depends on
whether it's a read or a write.

We accept the normal (SCSI) ioctls: they get handed through to the other
side which can then handle it or reply that it's unsupported.  It's
not clear that this actually works in general, since I don't know
if blk_pc_request() requests have an accurate rq_data_dir().

Although we try to reply -ENOTTY on unsupported commands, ioctl(fd,
CDROMEJECT) returns success to userspace.  This needs a separate
patch.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Rusty Russell 2007-10-22 11:03:38 +10:00
commit e467cde238
5 changed files with 367 additions and 0 deletions
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51
include/linux/virtio_blk.h Normal file
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#ifndef _LINUX_VIRTIO_BLK_H
#define _LINUX_VIRTIO_BLK_H
#include <linux/virtio_config.h>
/* The ID for virtio_block */
#define VIRTIO_ID_BLOCK 2
/* Feature bits */
#define VIRTIO_CONFIG_BLK_F 0x40
#define VIRTIO_BLK_F_BARRIER 1 /* Does host support barriers? */
/* The capacity (in 512-byte sectors). */
#define VIRTIO_CONFIG_BLK_F_CAPACITY 0x41
/* The maximum segment size. */
#define VIRTIO_CONFIG_BLK_F_SIZE_MAX 0x42
/* The maximum number of segments. */
#define VIRTIO_CONFIG_BLK_F_SEG_MAX 0x43
/* These two define direction. */
#define VIRTIO_BLK_T_IN 0
#define VIRTIO_BLK_T_OUT 1
/* This bit says it's a scsi command, not an actual read or write. */
#define VIRTIO_BLK_T_SCSI_CMD 2
/* Barrier before this op. */
#define VIRTIO_BLK_T_BARRIER 0x80000000
/* This is the first element of the read scatter-gather list. */
struct virtio_blk_outhdr
{
/* VIRTIO_BLK_T* */
__u32 type;
/* io priority. */
__u32 ioprio;
/* Sector (ie. 512 byte offset) */
__u64 sector;
/* Where to put reply. */
__u64 id;
};
#define VIRTIO_BLK_S_OK 0
#define VIRTIO_BLK_S_IOERR 1
#define VIRTIO_BLK_S_UNSUPP 2
/* This is the first element of the write scatter-gather list */
struct virtio_blk_inhdr
{
unsigned char status;
};
#endif /* _LINUX_VIRTIO_BLK_H */