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author | Linus Torvalds <torvalds@linux-foundation.org> | 2015-04-24 20:22:09 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-04-24 20:22:09 +0300 |
commit | c6668726d2c2c581e6c417448c472c994d026f5f (patch) | |
tree | ccbc5a73b9dfe09a065cb5d8627aa2297e730ec0 /Documentation/target/tcmu-design.txt | |
parent | 06b45f2aa703837163496f5db6a53575665cc6b4 (diff) | |
parent | 68d4cef3bab3fb9bb0dbac690ba35a96cb5a16d9 (diff) | |
download | linux-c6668726d2c2c581e6c417448c472c994d026f5f.tar.xz |
Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending
Pull SCSI target updates from Nicholas Bellinger:
"Lots of activity in target land the last months.
The highlights include:
- Convert fabric drivers tree-wide to target_register_template() (hch
+ bart)
- iser-target hardening fixes + v1.0 improvements (sagi)
- Convert iscsi_thread_set usage to kthread.h + kill
iscsi_target_tq.c (sagi + nab)
- Add support for T10-PI WRITE_STRIP + READ_INSERT operation (mkp +
sagi + nab)
- DIF fixes for CONFIG_DEBUG_SG=y + UNMAP file emulation (akinobu +
sagi + mkp)
- Extended TCMU ABI v2 for future BIDI + DIF support (andy + ilias)
- Fix COMPARE_AND_WRITE handling for NO_ALLLOC drivers (hch + nab)
Thanks to everyone who contributed this round with new features,
bug-reports, fixes, cleanups and improvements.
Looking forward, it's currently shaping up to be a busy v4.2 as well"
* 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending: (69 commits)
target: Put TCMU under a new config option
target: Version 2 of TCMU ABI
target: fix tcm_mod_builder.py
target/file: Fix UNMAP with DIF protection support
target/file: Fix SG table for prot_buf initialization
target/file: Fix BUG() when CONFIG_DEBUG_SG=y and DIF protection enabled
target: Make core_tmr_abort_task() skip TMFs
target/sbc: Update sbc_dif_generate pr_debug output
target/sbc: Make internal DIF emulation honor ->prot_checks
target/sbc: Return INVALID_CDB_FIELD if DIF + sess_prot_type disabled
target: Ensure sess_prot_type is saved across session restart
target/rd: Don't pass incomplete scatterlist entries to sbc_dif_verify_*
target: Remove the unused flag SCF_ACK_KREF
target: Fix two sparse warnings
target: Fix COMPARE_AND_WRITE with SG_TO_MEM_NOALLOC handling
target: simplify the target template registration API
target: simplify target_xcopy_init_pt_lun
target: remove the unused SCF_CMD_XCOPY_PASSTHROUGH flag
target/rd: reduce code duplication in rd_execute_rw()
tcm_loop: fixup tpgt string to integer conversion
...
Diffstat (limited to 'Documentation/target/tcmu-design.txt')
-rw-r--r-- | Documentation/target/tcmu-design.txt | 43 |
1 files changed, 28 insertions, 15 deletions
diff --git a/Documentation/target/tcmu-design.txt b/Documentation/target/tcmu-design.txt index 5518465290bf..43e94ea6d2ca 100644 --- a/Documentation/target/tcmu-design.txt +++ b/Documentation/target/tcmu-design.txt @@ -138,27 +138,40 @@ signals the kernel via a 4-byte write(). When cmd_head equals cmd_tail, the ring is empty -- no commands are currently waiting to be processed by userspace. -TCMU commands start with a common header containing "len_op", a 32-bit -value that stores the length, as well as the opcode in the lowest -unused bits. Currently only two opcodes are defined, TCMU_OP_PAD and -TCMU_OP_CMD. When userspace encounters a command with PAD opcode, it -should skip ahead by the bytes in "length". (The kernel inserts PAD -entries to ensure each CMD entry fits contigously into the circular -buffer.) - -When userspace handles a CMD, it finds the SCSI CDB (Command Data -Block) via tcmu_cmd_entry.req.cdb_off. This is an offset from the -start of the overall shared memory region, not the entry. The data -in/out buffers are accessible via tht req.iov[] array. Note that -each iov.iov_base is also an offset from the start of the region. - -TCMU currently does not support BIDI operations. +TCMU commands are 8-byte aligned. They start with a common header +containing "len_op", a 32-bit value that stores the length, as well as +the opcode in the lowest unused bits. It also contains cmd_id and +flags fields for setting by the kernel (kflags) and userspace +(uflags). + +Currently only two opcodes are defined, TCMU_OP_CMD and TCMU_OP_PAD. + +When the opcode is CMD, the entry in the command ring is a struct +tcmu_cmd_entry. Userspace finds the SCSI CDB (Command Data Block) via +tcmu_cmd_entry.req.cdb_off. This is an offset from the start of the +overall shared memory region, not the entry. The data in/out buffers +are accessible via tht req.iov[] array. iov_cnt contains the number of +entries in iov[] needed to describe either the Data-In or Data-Out +buffers. For bidirectional commands, iov_cnt specifies how many iovec +entries cover the Data-Out area, and iov_bidi_count specifies how many +iovec entries immediately after that in iov[] cover the Data-In +area. Just like other fields, iov.iov_base is an offset from the start +of the region. When completing a command, userspace sets rsp.scsi_status, and rsp.sense_buffer if necessary. Userspace then increments mailbox.cmd_tail by entry.hdr.length (mod cmdr_size) and signals the kernel via the UIO method, a 4-byte write to the file descriptor. +When the opcode is PAD, userspace only updates cmd_tail as above -- +it's a no-op. (The kernel inserts PAD entries to ensure each CMD entry +is contiguous within the command ring.) + +More opcodes may be added in the future. If userspace encounters an +opcode it does not handle, it must set UNKNOWN_OP bit (bit 0) in +hdr.uflags, update cmd_tail, and proceed with processing additional +commands, if any. + The Data Area: This is shared-memory space after the command ring. The organization |