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Diffstat (limited to 'xen/include/public/io/blkif.h')
| -rw-r--r-- | xen/include/public/io/blkif.h | 115 |
1 files changed, 115 insertions, 0 deletions
diff --git a/xen/include/public/io/blkif.h b/xen/include/public/io/blkif.h new file mode 100644 index 0000000000..8cd3696eb6 --- /dev/null +++ b/xen/include/public/io/blkif.h @@ -0,0 +1,115 @@ +/****************************************************************************** + * blkif.h + * + * Unified block-device I/O interface for Xen guest OSes. + * + * Copyright (c) 2003-2004, Keir Fraser + */ + +#ifndef __XEN_PUBLIC_IO_BLKIF_H__ +#define __XEN_PUBLIC_IO_BLKIF_H__ + +#define blkif_vdev_t u16 +#define blkif_sector_t u64 + +#define BLKIF_OP_READ 0 +#define BLKIF_OP_WRITE 1 +#define BLKIF_OP_PROBE 2 + +/* NB. Ring size must be small enough for sizeof(blkif_ring_t) <= PAGE_SIZE. */ +#define BLKIF_RING_SIZE 64 + +/* + * Maximum scatter/gather segments per request. + * This is carefully chosen so that sizeof(blkif_ring_t) <= PAGE_SIZE. + * NB. This could be 12 if the ring indexes weren't stored in the same page. + */ +#define BLKIF_MAX_SEGMENTS_PER_REQUEST 11 + +typedef struct { + u8 operation; /* 0: BLKIF_OP_??? */ + u8 nr_segments; /* 1: number of segments */ + blkif_vdev_t device; /* 2: only for read/write requests */ + unsigned long id; /* 4: private guest value, echoed in resp */ + blkif_sector_t sector_number; /* start sector idx on disk (r/w only) */ + /* @f_a_s[2:0]=last_sect ; @f_a_s[5:3]=first_sect ; @f_a_s[:12]=frame. */ + /* @first_sect: first sector in frame to transfer (inclusive). */ + /* @last_sect: last sector in frame to transfer (inclusive). */ + /* @frame: machine page frame number. */ + unsigned long frame_and_sects[BLKIF_MAX_SEGMENTS_PER_REQUEST]; +} PACKED blkif_request_t; + +#define blkif_first_sect(_fas) (((_fas)>>3)&7) +#define blkif_last_sect(_fas) ((_fas)&7) + +typedef struct { + unsigned long id; /* copied from request */ + u8 operation; /* copied from request */ + s16 status; /* BLKIF_RSP_??? */ +} PACKED blkif_response_t; + +#define BLKIF_RSP_ERROR -1 /* non-specific 'error' */ +#define BLKIF_RSP_OKAY 0 /* non-specific 'okay' */ + +/* + * We use a special capitalised type name because it is _essential_ that all + * arithmetic on indexes is done on an integer type of the correct size. + */ +typedef u32 BLKIF_RING_IDX; + +/* + * Ring indexes are 'free running'. That is, they are not stored modulo the + * size of the ring buffer. The following macro converts a free-running counter + * into a value that can directly index a ring-buffer array. + */ +#define MASK_BLKIF_IDX(_i) ((_i)&(BLKIF_RING_SIZE-1)) + +typedef struct { + BLKIF_RING_IDX req_prod; /* 0: Request producer. Updated by front-end. */ + BLKIF_RING_IDX resp_prod; /* 4: Response producer. Updated by back-end. */ + union { /* 8 */ + blkif_request_t req; + blkif_response_t resp; + } PACKED ring[BLKIF_RING_SIZE]; +} PACKED blkif_ring_t; + + +/* + * BLKIF_OP_PROBE: + * The request format for a probe request is constrained as follows: + * @operation == BLKIF_OP_PROBE + * @nr_segments == size of probe buffer in pages + * @device == unused (zero) + * @id == any value (echoed in response message) + * @sector_num == unused (zero) + * @frame_and_sects == list of page-sized buffers. + * (i.e., @first_sect == 0, @last_sect == 7). + * + * The response is a list of vdisk_t elements copied into the out-of-band + * probe buffer. On success the response status field contains the number + * of vdisk_t elements. + */ + +/* XXX SMH: Type values below are chosen to match ide_xxx in Linux ide.h. */ +#define VDISK_TYPE_FLOPPY 0x00 +#define VDISK_TYPE_TAPE 0x01 +#define VDISK_TYPE_CDROM 0x05 +#define VDISK_TYPE_OPTICAL 0x07 +#define VDISK_TYPE_DISK 0x20 + +#define VDISK_TYPE_MASK 0x3F +#define VDISK_TYPE(_x) ((_x) & VDISK_TYPE_MASK) + +/* The top two bits of the type field encode various flags. */ +#define VDISK_FLAG_RO 0x40 +#define VDISK_FLAG_VIRT 0x80 +#define VDISK_READONLY(_x) ((_x) & VDISK_FLAG_RO) +#define VDISK_VIRTUAL(_x) ((_x) & VDISK_FLAG_VIRT) + +typedef struct { + blkif_sector_t capacity; /* 0: Size in terms of 512-byte sectors. */ + blkif_vdev_t device; /* 8: Device number (opaque 16 bit value). */ + u16 info; /* 10: Device type and flags (VDISK_*). */ +} PACKED vdisk_t; /* 12 bytes */ + +#endif /* __XEN_PUBLIC_IO_BLKIF_H__ */ |